title: Effects of pornography

text: Pornography has many different forms which are difficult to cover in blanket form. Pornographic internet videos, for example, have been found to have different effects on viewers than material such as pornographic magazines. Within the field of pornography research, there are also other challenges that arise due to strong opinions and feelings on the topic. Confirmation bias has been prevalent on both sides due to societal taboos surrounding pornography. Studies have looked into both negative effects of pornography as well as potential benefits or positive effects of pornography. A large percentage of studies suffer from methodological issues. In one meta-study by researchers at Middlesex University in England, over 40,000 papers and articles were submitted to the team for review: 276 or 0.69% were suitable for consideration due to the low quality of research within the field.


title: Effects of pornography

text: One limitation to current research about pornography's effect on relationships is the sample. Researchers often, but not always, sample individuals who are in a relationship. They rarely sample both partners. This method limits the scope of research as pornography can affect a relationship depending on how often one or both partners watch and if they watch alone or together. For example, a Norwegian study on heterosexual partners evaluated these effects. The study found that couples experience higher levels of dysfunction when only one partner is watching alone. Partners who both watch pornography alone experienced low levels of dysfunction. Partners who did not watch at all experienced an average level of dysfunction.


title: Effects of pornography

text: Men who consume pornography regularly have reported less stable mental health, specifically higher levels of depression. Pornography can be considered addictive, especially in men.


title: Effects of pornography

text: Pornography addiction is a purported behavioral addiction characterized by compulsive, repeated use of pornographic material which causes serious consequences to one's physical, mental, social, and/or financial well-being. There is no diagnosis of pornography addiction in the current "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5), though the DSM-5 considered the diagnosis of hypersexuality-related behavioral disorders (to which porn addiction was a subset), but rejected it because "there is insufficient peer-reviewed evidence to establish the diagnostic criteria and course descriptions needed to identify these behaviors as mental disorders." Instead, some psychologists suggest that any maladaptive sexual symptoms represent a manifestation of an underlying disorder, such as depression or anxiety which is simply manifesting itself sexually, or, alternatively, there is no underlying disorder and the behavior simply is not maladaptive. It is argued that psychologists do not recognize the concept of addiction, only chemical dependence, and some believe the concept and diagnosis to be stigmatizing and unhelpful.


title: Effects of pornography

text: Two 2016 neurology reviews found evidence of addiction related brain changes in internet pornography users. Psychological effects of these brain changes are described as desensitization to reward, a dysfunctional anxiety response, and impulsiveness. Another 2016 review suggests that internet behaviors, including the use of pornography, be considered potentially addictive, and that problematic use of online pornography be considered an "internet-use disorder".


title: Effects of pornography

text: Introductory psychology textbook authors Coon, Mitterer and Martini, passingly mentioning NoFap (former pornography users who have since chosen to abstain from the material) speak of pornography as a "supernormal stimulus" but use the model of compulsion rather than addiction.


title: Effects of pornography

text: A number of studies have found neurological markers of addiction in Internet porn users, which is consistent with a large body of research finding similar markers in other kinds of problematic internet users. Yet other studies have found that critical biomarkers of addiction are missing.


title: Effects of pornography

text: According to the American Society of Addiction Medicine, some psychological and behavioral changes characteristic of addiction brain changes include addictive cravings, impulsiveness, weakened executive function, desensitization, and dysphoria. BOLD fMRI results have shown that individuals diagnosed with compulsive sexual behavior (CSB) show enhanced cue reactivity in brain regions associated traditionally with drug-cue reactivity. These regions include the amygdala and the ventral striatum. Men without CSB who had a long history of viewing pornography exhibited a less intense response to pornographic images in the left ventral putamen, possibly suggestive of desensitization. ASAMs position is inconsistent with the American Association of Sex Educators, Counselors, and Therapists, who cite lack of strong evidence for such classification, describing ASAM as not informed by "accurate human sexuality knowledge".


title: Effects of pornography

text: Neuropsychopharmacological and psychological researches on pornography addiction conducted between 2015 and 2021 have concluded that most studies have been focused entirely or almost exclusively on men in anonymous settings, and the findings are contradicting. Some researches support the idea that pornography addiction qualifies as a form of behavioral addiction into the umbrella construct of hypersexual behavior and/or a subset of compulsive sexual behavior (CSB), and should be treated as such, whereas others have detected the increased activation of ventral striatal reactivity in men for cues predicting erotic but not monetary rewards and cues signaling erotic pictures, therefore suggesting similarities between pornography addiction and conventional addiction disorders.


title: Effects of pornography

text: ICD-11 added pornography to CSBD. CSBD is not an addiction and should not be conflated with sex addiction.


title: Effects of pornography

text: Some clinicians and support organizations recommend voluntary use of Internet content-control software, internet monitoring, or both, to manage problematic online pornography use. Sex researcher Alvin Cooper and colleagues suggested several reasons for using filters as a therapeutic measure, including curbing accessibility that facilitates problematic behavior and encouraging clients to develop coping and relapse prevention strategies. Cognitive therapist Mary Anne Layden suggested that filters may be useful in maintaining environmental control. Internet behavior researcher David Delmonico stated that, despite their limitations, filters may serve as a "frontline of protection."


title: Effects of pornography

text: Rothman stated "The professional public health community is not behind the recent push to declare pornography a public health crisis." She and another researcher have called these moves a "political stunt".


title: Effects of pornography

text: Individuals who have developed form of dependence on pornography use, and do consider themselves as addicted to pornography, have experienced withdrawal symptoms. A study on effects and consumption of pornography across large sample of students from various universities has shown more than a half tried to give up consumption for pornography (or at least minimize the use of such material). Within those who at least made one attempt, almost 75% experienced at least one symptom of withdrawal. Withdrawal symptoms included erotic dreams, irritability, attention disturbance, and sense of loneliness. Other recorded potential symptoms included depression, anxiety, obsessive thoughts, and an intense longing for pornography. On topic on anxiety, a survey performed on a sample of internet users with porn dependency, concluded 24% of the participants had experienced anxiety symptoms if access to porn on the Internet was inhibited. Individuals who showcased an abstinence from online pornography has shown "most common positive effects" to include improvements in day-to-day functioning, increased energy, mental clarity and productivity. Some surveyed individuals even experienced enhanced sensation and greater pleasure from ordinary activities.


title: Effects of pornography

text: A study of 359 college men found that high viewership of pornography relates to increased masculinity and body dissatisfaction. Sexual performance changes a man's view of his masculinity, and often his self-esteem. Pornography is not the only factor affecting men's self-esteem and body image. Popular media often depicts strong but lean men. Pornography is significant to men's self-image. It connects a lean body type to sexual validation. As of 2021, few studies have evaluated how exposure to pornography relates to men's body image. Researchers recommend that others conduct more studies on pornography's effect on men's psychology.


title: Effects of pornography

text: Heterosexual pornography reinforces a concept called the centerfold syndrome. In 1995, psychologist Gary R. Brooks wrote about men and the centerfold syndrome. This concept asserted that gender roles in media contribute to high sexual dysfunction in men. Sexual dysfunction has many parts. One part is the viewing of women as body parts, trophies, or sexual conquests. These concepts are often known as voyeurism, objectification, and trophyism. Another part is tying female approval of manliness to a man's self-image. The third part of sexual dysfunction includes avoiding intimacy, attachment, and emotions. Heterosexual pornography reinforces this syndrome through observational learning. In other words, the story within pornography becomes the expected reality. Deviations from that story create low self-esteem.


title: Effects of pornography

text: Studies rarely observe women's viewership of pornography. One modern study with female subjects provided mixed results. Pornography does not affect women's perception of body image and relationship satisfaction if it is free of behavior. Violence is one example. All other viewership appears to minimally affect body image and relationship satisfaction.


title: Effects of pornography

text: A 2021 study has shown a mediating role of pornography use among women and how it affects the consciousness of body image and attachment insecurities. Girls who have not experienced a sensitive response to their needs and/or were emotionally deprived under the parent/caretaker childhood environment had a greater chance of developing insecurities about their body image. The use of pornography seems to amplify attachment fears and anxiety. Such anxiety is correlated to females seeking approval of their bodies and self-worth from their counterpart in a relationship setting. The findings did correlate with past research articles which found that "anxious but not avoidant attachment affects body image, the drive for thinness, body dissatisfaction and body appreciation." Furthermore, pornography use could also amplify women's body image self-consciousness in an intimate setting. The acts performed in pornographic movies created a feeling of pressure among women, not only creating a higher negative body image but also the feeling of being criticized by their partners if their body was not resembling the body shape of models in pornographic content. However, mediating role between pornography, and anxiety attachment, and body image self-consciousness was found only in women in a relationship at the time of the study, which correlated with attachment theory.


title: Effects of pornography

text: A 2019 survey of 1083 U.S. adults evaluated the relationship between pornography and unethical behavior in the workplace. Unethical behavior, according to the researchers, consists of delay discounting and dehumanization. Delay discounting involves the idea of waiting versus acting now and future reward. It is to expect lower rewards in the future versus when acting now. The expectation of a high reward for acting now can lead to reduced self-control and increased impulsivity. Dehumanization is a form of moral disengagement in which people view others as less than human. According to the study, increased pornography use causes increased dehumanization and unethical behavior.


title: Effects of pornography

text: The sexual effects of pornography on intimacy and relationships observe some of the most gendered differences. Men and women differ vastly in how they are impacted by pornography both within and beyond a romantic or sexual relationship.


title: Effects of pornography

text: The consumption of pornography has been shown to have an impact on sexual risk-taking, including less frequent usage of condoms and birth control, as well as more casual sexual encounters. It can negatively impact sexual functioning, especially in men. However, pornography can function as an educational resource for individuals to improve their sexual knowledge, and women who consume pornography more regularly experience increased desire for sexual activity, indicating that pornography might be useful as a form of foreplay.


title: Effects of pornography

text: Sexual desire is one of the factors most strongly moderated by gender differences. In general, men experience the most acute effects from pornography in terms of sexual desire. Straight men report less sexual desire, both for their partner and in general, directly after consuming pornography. Men also typically utilize pornography for masturbation and solo-sexual activities, rather than partnered or joint purposes. Strong associations exist between increased pornography consumption, as well as frequency of pornography consumption, and problematic decreases in sexual desire for men. Men who more frequently use pornography report less desire for their partner, and less desire for sex in general.


title: Effects of pornography

text: While most modern research on pornography focuses on men, the findings in women hold interesting information on pornography's gendered impact on sexual desire. Women have found a positive correlation between pornography consumption and sexual desire, indicating that women who view pornography feel more positively about expressing their sexual desire. In addition to increased sexual desire, women also express more sexual desire specifically for their partner on days when they watch pornography, indicating pornography may function as a form of foreplay.


title: Effects of pornography

text: Although men and women do differ in many significant ways with respect to pornography consumption and sexual behavior, they share one important similarity: brain activity. Men and women's brain activity while watching pornography is nearly identical, suggesting that both men and women experience similar arousal while watching pornography. Further, both men and women report significant support for female-centric pornography, though men express similar levels of arousal to both traditional male-centric pornography as well as female-centric pornography. While women report more general negativity towards traditional, male-centric pornography, women express stronger support and higher levels of self-reported arousal for female-centric pornography.


title: Effects of pornography

text: In general, pornography consumption in couples has been associated with greater sexual desire. Although research in the way of same-sex relationships is limited, available findings indicate that pornography use is connected to an increased level of sexual desire. Men partnered with women report less sexual desire in general with increased pornography consumption, whereas women in both mixed-sex or same-sex relationships report greater sexual desire overall. Also, individuals were less likely to consume pornography the day after engaging in sexual intercourse.


title: Effects of pornography

text: In 2016, model and actress Pamela Anderson and Orthodox Rabbi Shmuley Boteach co-authored a viral "Wall Street Journal" opinion piece, in which they called online pornography a "public hazard of unprecedented seriousness."


title: Effects of pornography

text: Sexual function is a rising concern with pornography consumption. Primarily thought to affect men, there is a notable relationship between pornography consumption and sexual function problems. Commonly reported problems include erectile dysfunction, delayed ejaculation, anorgasmia, and a lack of sexual desire. Recently, rates of sexual dysfunction have been increasing in younger age brackets. Medical professionals suspect pornography may be one factor contributing to this increase, however there is little causal evidence of such an effect. Another issue is delayed ejaculation, during which men may experience a large disconnect between their orgasm and ejaculation, or difficulty achieving ejaculation. Overarching research shows little evidence of pornography having any effect on delayed ejaculation. Despite the lack of evidence for more physical issues with sexual function, pornography is related to problematic decreases of sexual desire and sexual satisfaction, though the direction of this relationship remains up for debate without additional causal research.


title: Effects of pornography

text: In women, there is little evidence for pornography-induced sexual dysfunction. The most commonly observed effect is increased anxiety or distress, which may then lead to issues of sexual function. The most commonly reported issue for women is arousal dysfunction, indicating a difficulty in achieving or maintaining arousal during sexual activity. This could potentially lead to physical issues, such as painful penetration or vaginismus, making sexual intercourse painful and unpleasant. Women also tend to report more negative effects with regards to pornography, including strong feelings of shame or guilt.


title: Effects of pornography

text: For both men and women, pornography may lead individuals to make riskier decisions with their sexual health. A study analyzing the use of barrier contraceptives by German adults found that, when pornography is viewed as an educational resource, there is an inverse relationship between pornography consumption and condom usage; people who viewed more pornography tended to not use condoms as frequently. Overall, the most frequently reported issues with sexual function that relate to pornography are decreases in sexual desire for men, and decreases in sexual satisfaction overall.


title: Effects of pornography

text: Research on pornography's effect on sexual satisfaction is highly varied. Numerous studies looking at both individuals and couples have found different, at times contradictory, results. One study found a negative relationship between pornography consumption and sexual satisfaction across two samples of men. In addition, frequency of pornography consumption, rather than the type of pornography consumed, is negatively correlated with sexual satisfaction; the type of pornography an individual consumed had no effect on sexual satisfaction. When considering couples and their pornography consumption, couples with a greater discordance reported being more sexually dissatisfied than couples who watched pornography together, as well as couples who jointly abstained from pornography altogether.


title: Effects of pornography

text: When looking at women, there is a positive correlation between pornography consumption and sexual satisfaction. Some suggest the connection between male pornography use and sexual dissatisfaction may be the other way around, with men resorting to pornography due to sexual satisfaction, or even perhaps a cyclical effect. An indirect, yet positive, effect on sexual satisfaction has been found when looking at sexual preference.


title: Effects of pornography

text: Individuals who use pornography alongside masturbation as the primary tool of sexual arousal and fulfillment of one's sexual satisfaction (or needs) may become conditioned to prefer pornography more than other needs of sexual arousal. Furthermore, the "frequency of pornography consumption was also directly related to a relative preference for pornographic rather than partnered sexual excitement." The individuals in the given study primarily used pornography for masturbation purposes. Such preference of pornography over sexual satisfaction fulfilled with a partner, especially in the case of extracting sexual information from pornography, would lead to lower overall sexual satisfaction. Individuals who seek pornography as the main source of information about sexuality were associated with lower sexual excitement, and in return, lower sexual satisfaction in a partnered relationship. Gender did not affect the results of such findings.


title: Effects of pornography

text: However, pornography among some individuals is not only used for sexual satisfaction. A study on affection substitution has shown that "pornography consumption is positively related to affection deprivation, depression, and loneliness and inversely related to experienced affection, relational satisfaction, and closeness." All presented above variants, except affection deprivation, had a significant correlation based on statistical data. Due to such positive relations, individuals who consume pornography not only use it to satisfy their sexual arousal but also to reduce loneliness and create a coping mechanism against social disconnection. Some of the examples of coping mechanisms may include "creating parasocial relationships with the characters depicted in pornography."


title: Effects of pornography

text: The use of pornography is extremely varied, especially in the United States. Consumption rates —including general consumption, frequency of consumption, length of time, and type of pornography— vary by gender, age, and relationship status, as well as frequency of consumption, which all factor into overall pornography consumption rates. In general, men consume more pornography, and consume pornography more frequently, than women. A vast majority of men report having consumed pornography, with rates ranging from 50% to 90%, usually plateauing in the upper 80% range. Women, however, report significantly less and significantly more varied consumption of pornography, with between 30% and 80% of women saying they have viewed pornography in their lifetime. This variation reflects differences in nationality and culture in terms of sex positivity and pornography acceptance, as well as the unreliability of self-reporting. Despite the variation and lower reports of pornography consumption for women, female viewership of pornography is steadily increasing. Women tend to prefer less hardcore porn compared to men, and men report consuming pornography in conjunction with masturbation more frequently than women.


title: Effects of pornography

text: One of the more current findings revolves around how pornography impacts sexual preference. Theories speculate that increase pornography consumption may alter an individual's preferences during sexual intercourse to more closely resemble what is depicted in pornography. This may include both the acts depicted, as well as the behaviors displayed by actors. Among men, there is a positive relationship between pornography consumption and a desire for more porn-like sexual experience. Frequency of consumption and type of pornography consumed are related to increased desire for more porn-like sex, which is measured by items indicating an expressed preference for "kinkier sex," "hotter sex," and a more porn-like "sexual appearance." The latter includes grooming habits, as well as hair color and body type. While correlational, the findings do present evidence that pornography consumption has a role in sexual preferences, though causal relationships cannot be confirmed. This effect is mitigated by both the type of pornography consumed, as well as the frequency of pornography consumption, and the finding holds for both men and women.


title: Effects of pornography

text: A study by Professor Kathryn C. Seigfried-Spellar and Professor Marcus Rogers found results which suggested deviant pornography use followed a Guttman-like progression, concluding that individuals with a younger "age of onset" for adult pornography use were more likely to engage in deviant pornography (bestiality or child) compared to those with a later "age of onset".


title: Effects of pornography

text: Prolonged exposure to pornographic content can lead to a development of increased sexual stimuli tolerance. Study showed earlier exposure may lead to potential desensitization to the stimuli, meaning individuals seek longer stimulation (12.0%) and more intensive sexual stimuli (17.6%) to reach climax. Such increase in tolerance was connected to a change in online pornography use pattern, major one's being "switching to a novel genre of explicit material (46.0%), use of materials that do not match sexual orientation (60.9%) and need to use more extreme (violent) material (32.0%)."


title: Effects of pornography

text: A cross-sectional study on prevalence and patterns in pornography use has detected individuals who mentioned an increased need for more extreme content. Although this may have been depicted as a result of desensitization due to frequent use of pornography, thus a need to use more graphic, violent, and degrading porn material to achieve similar sexual arousal, the actual causation comes from aggression as "more extreme pornography material was more frequently reported by males describing themselves as aggressive." On the other hand, females who increased their search for extreme pornographic content came from the curiosity aspect itself rather than a need due to desensitization.


title: Effects of pornography

text: The research focused on associations of dark personality traits with online activities has also found some dark traits related to online sexual use. Specific online activities of the study covered social media, online gaming, online gambling, online shopping and online sex. The results showed that "Machiavellianism, spitefulness, sadism, and narcissism were related to different types of internet activities such as online sex, social media use, online gambling, online gaming, and online shopping." Individuals' correlation to sexual use to such study variables is Machiavellianism (.32), spitefulness (.31), sadism (.34), narcissism (.24), and psychopathy (.26).


title: Effects of pornography

text: A controlled study describes the relationship between given behaviors or environmental conditions and health effects in a laboratory setting in which conditions other than those under study are effectively held constant across groups of participants receiving various levels of the experimental condition(s). Since it is considered that the only functional difference between groups is the level of experimental condition(s) received, researchers can strongly infer cause-and-effect relationships from statistically significant associations between experimental condition(s) and health consequences. Thus, if executed properly, controlled studies have high levels of internal validity. However, such studies often suffer from questionable external validity due to the considerable differences between real-world environments and the experimental context, and the consequent belief that results cannot be generalized beyond that context.


title: Effects of pornography

text: The link between pornography and sexual aggression has been the subject of multiple meta-analyses. Meta-analyses conducted in the 1990s suggested to researchers that there might not be an association of any kind between pornography and rape supportive attitudes in non-experimental studies. However, a meta-analysis by Hald, Malamuth and Yuen (2000) suggests that there is a link between consumption of violent pornography and rape-supportive attitudes in certain populations of men, particularly when moderating variables are taken into consideration.


title: Effects of pornography

text: A meta-analysis conducted in 2015 found that pornography "consumption was associated with sexual aggression in the United States and internationally, among males and females, and in cross-sectional and longitudinal studies. Associations were stronger for verbal than physical sexual aggression, although both were significant. The general pattern of results suggested that violent content may be an exacerbating factor."


title: Effects of pornography

text: An earlier review of this literature by Ferguson and Hartley in 2009 argued that "it is time to discard the hypothesis that pornography contributes to increased sexual assault behavior". They stated that the authors of some studies tended to highlight positive findings while de-emphasizing null findings and concluded that controlled studies, on balance, were not able to support links between pornography and sexual violence.


title: Effects of pornography

text: Ferguson and Hartley updated their review with a 2020 meta-analysis. This meta-analysis concluded that mainstream pornography could not be linked to sexual violence and was associated with reductions in sexual violence at the societal level. Small correlations were found between violent porn viewing and sexual aggression, but evidence was unable to differentiate whether this was a causal or selection effect (i.e. sexual offenders seeking out violent porn).


title: Effects of pornography

text: Rothman stated in 2021: "In other words, five studies found that the sexual violence perpetrators had seen "less" pornography than other criminals." She added "Should these few “bad apples” spoil the pleasure of the potentially much larger subset of people who enjoy violent-looking pornography with no ill effects?"


title: Effects of pornography

text: An epidemiological study describes the association between given behaviors or environmental conditions, and physical or psychological health by means of observation of real-world phenomena through statistical data. Epidemiological studies generally have high levels of external validity, insofar as they accurately describe events as they occur outside of a laboratory setting, but low levels of internal validity, since they do not strongly establish cause-and-effect relationships between the behaviors or conditions under study, and the health consequences observed.


title: Effects of pornography

text: Danish criminologist Berl Kutchinsky's "Studies on Pornography and sex crimes in Denmark" (1970), a scientific report ordered by the Presidential Commission on Obscenity and Pornography, found that the legalizing of pornography in Denmark had not resulted in an increase of sex crimes. In 1998 Milton Diamond from the University of Hawaii noted that in Japan, the number of reported cases of child sex abuse dropped markedly after the ban on sexually explicit materials was lifted in 1969; however, in Denmark and Sweden, there was a very slight increase in reported rapes after the liberalization of their pornography laws during the same time period, which scientists attribute to a higher awareness of what amounts to sex abuse.


title: Effects of pornography

text: Some researchers argue that there is a correlation between pornography and a decrease of sex crimes. "The effects of Pornography: An International Perspective" was an epidemiological study which found that the massive growth of the pornography industry in the United States between 1975 and 1995 was accompanied by a substantial decrease in the number of sexual assaults per capita - and reported similar results for Japan.


title: Effects of pornography

text: In 1986, a review of epidemiological studies by Neil M. Malamuth found that the quantity of pornographic material viewed by men was positively correlated with degree to which they endorsed sexual assault. Malamuth's work describes Check (1984), who found among a diverse sample of Canadian men that more exposure to pornography led to higher acceptance of rape myths, violence against women, and general sexual callousness. In another study, Briere, Corne, Runtz and Neil M. Malamuth, (1984) reported similar correlations in a sample involving college males. On the other hand, the failure to find a statistically significant correlation in another previous study led Malamuth to examine other interesting correlations, which took into account the information about sexuality the samples obtained in their childhood, and pornography emerged as the second most important source of information. Malamuth's work has been criticized by other authors, however, such as Ferguson and Hartley (2009) who argue Malamuth has exaggerated positive findings and has not always properly discussed null findings. In a "Quartz" publication, Malamuth argued that porn is like alcohol: "whether it's bad for you depends on who you are" (stating that it increases violence in a few people, not in most people; it makes most people more relaxed).


title: Effects of pornography

text: The consumption of pornography has a large reach across various areas of relationships in life. Pornography can influence an individual's relationship and intimacy through a number of channels, including overall level of satisfaction in their relationships, communication within a relationship, and setting boundaries for infidelity within a relationship.


title: Effects of pornography

text: Pornography's impact on relationship satisfaction comes under scrutiny, as findings range from negative correlations, to positive relationships. Pornography consumption is correlated with less relationship satisfaction, sexual satisfaction, and in men, less sexual desire for their partner. Researchers have concluded this could be because the novelty value of porn makes it difficult for a female partner to compete. Some research reports positive findings for women who consume pornography more regularly, including increased relationship satisfaction and decreased distress.


title: Effects of pornography

text: The research on the relationship between pornography use and relationship satisfaction is vast and mixed. While some believe pornography consumption leads people to become less satisfied in their relationships, others believe it can have the direct opposite effect. Pornography consumption tends to accompany lower levels of satisfaction in long-term, heterosexual relationships. Most of the current research is correlational, indicating a connection but not a cause; however, one major trend is the rate of divorce. Couples who increase their consumption of pornography are nearly twice as likely to divorce than couples who do not, with the rate rising from 5% to 11%. Also, married adults who watch porn are twice as likely to be divorced after 6 years than married adults who don't watch porn. One mitigator is the frequency of pornography consumption. More frequent pornography consumption is negatively associated with relationship satisfaction. Individuals who report more frequent use of pornography within a relationship also report low levels of satisfaction in their relationships.


title: Effects of pornography

text: However, many reject the idea that pornography is inherently harmful to relationship satisfaction. Joint pornography consumption within a relationship has been connected to increased levels of relationship satisfaction for both partners. Couples who consumed pornography together expressed more satisfaction with their relationships than couples in which only one individual used pornography. This suggests that there is more at play than simply the consumption of pornography, such as the role of honesty and partner perception. Individuals whose partners are honest about their own pornography consumption tend to feel more satisfied in their relationships, to a point. There is evidence for an "honesty threshold," indicating that the relationship between honesty and pornography is not linear, and partners do not want to hear every detail about the other's pornography habits. This indicates that, although honesty and disclosure is important for pornography consumption, there seems to be a threshold of helpful honesty that, once surpassed, may cause more harm. In addition, when women consume pornography, they report lower levels of distress than their counterparts. While women often consume pornography less often than men, men are fairly accurate at perceiving their partner's pornography consumption. Women, on the other hand, are less accurate at perceiving their male partner's pornography use.


title: Effects of pornography

text: Some research suggests that there is no connection between relationship satisfaction and pornography use, whether individually or jointly. Although finding evidence in their second study for a negative correlation, a study of two independent male samples found no relationship between pornography and relationship satisfaction in their first sample. Conversely, other studies found no relationship whatsoever between joint pornography use and satisfaction. When analyzing couples and their pornography consumption over the course of one month, researchers found no correlation between relationship satisfaction and pornography use.


title: Effects of pornography

text: Communication is a vital component of any healthy relationship, and many researchers question how pornography may impact the ability of a couple to communicate openly. Honesty has been shown to be a mitigator in relationship effects of pornography consumption. Couples in which partners are honest about their pornography consumption report greater satisfaction than couples dealing with concealment, or dishonesty, surrounding pornography use. Pornography consumption among couples leads to improved communication about sexual desires, and increased openness in communication. Conversely, active concealment of pornography use habits can lead to less openness in communication and trust.


title: Effects of pornography

text: Another important aspect is the communication of affection within relationships. Affection Exchange Theory establishes the inherent role of affection within romantic relationships, and even in the role of survival, reproduction, and sexual selection. Trait attachment is positively associated with relationship satisfaction. Individuals who score higher in trait attachment report feeling and expressing greater sexual desire for their partners, compared to individuals who score lower in trait attachment. Some evidence indicates that the connection between Affection Exchange Theory and sexual desire is, in fact, stronger than the connection to relationship satisfaction, suggesting that sexual desire may have a crucial moderating role between the two. While this study found no correlation between pornography consumption and trait affection, researchers noted that increased feelings of guilt were related to lower levels of sexual desire for one's partner. This is somewhat indicative of partner-imposed or communicated guilt, or possibly reflecting an effect of the sexual scripts of pornography creating unrealistic expectations that lead to magnified dissatisfaction.


title: Effects of pornography

text: Because the creation of pornography involves unsimulated sex, usually without condoms (barebacking), pornographic actors have been found to be particularly vulnerable to sexually transmitted diseases.


title: Effects of pornography

text: The AIDS Healthcare Foundation tried several times to have California's Department of Industrial Relations, Division of Occupational Safety and Health's Appeals Board force companies in the pornography industry to treat actors and actresses as employees subject to occupational safety and health regulation. In a 2014 case brought against Treasure Island Media, an administrative judge ruled that the company had to comply with the regulations.


title: Effects of pornography

text: In the United Kingdom, the Association of Teachers and Lecturers feels schoolchildren need to be educated about pornography and warned what is reasonable and what is unacceptable. The UK children's commissioner initiated a meta-study conducted by researchers at Middlesex University which concluded that pornography is linked to unrealistic attitudes about sex, beliefs that women are sex objects, more frequent thoughts about sex, and found that children and young people who view pornography tend to hold less progressive gender role attitudes. Miranda Horvath stated about this: "But it is not possible to establish causation from correlational studies, and to say whether pornography is changing or reinforcing attitudes."


title: Effects of pornography

text: The Journal of Adolescence concluded in 2019 that the adolescent brain, due to its immature development, may be more sensitive to sexually explicit material, but due to a lack of empirical research, no firm conclusions can be drawn.


title: Effects of pornography

text: There are considerable ethical problems with performing some kinds of research on the effects of pornography use on minors. For example, Rory Reid (UCLA) declared, "Universities don't want their name on the front page of a newspaper for an unethical study exposing minors to porn."


title: Hypocrisy

text: Hypocrisy is the practice of engaging in the same behavior or activity for which one criticizes another or the practice of claiming to have moral standards or beliefs to which one's own behavior does not conform. In moral psychology, it is the failure to follow one's own expressed moral rules and principles. According to British political philosopher David Runciman, "Other kinds of hypocritical deception include claims to knowledge that one lacks, claims to a consistency that one cannot sustain, claims to a loyalty that one does not possess, claims to an identity that one does not hold". American political journalist Michael Gerson says that political hypocrisy is "the conscious use of a mask to fool the public and gain political benefit".


title: Hypocrisy

text: Hypocrisy has been a subject of folk wisdom and wisdom literature from the beginnings of human history. Increasingly, since the 1980s, it has also become central to studies in behavioral economics, cognitive science, cultural psychology, decision making, ethics, evolutionary psychology, moral psychology, political sociology, positive psychology, social psychology, and sociological social psychology.


title: Hypocrisy

text: The word "hypocrisy" comes from the Greek ὑπόκρισις ("hypokrisis"), which means "jealous", "play-acting", "acting out", "coward" or "dissembling". The word "hypocrite" is from the Greek word ὑποκριτής ("hypokritēs"), the agentive noun associated with ὑποκρίνομαι (hypokrinomai κρίση, "judgment" »κριτική (kritikē), "critics") presumably because the performance of a dramatic text by an actor was to involve a degree of interpretation, or assessment.


title: Hypocrisy

text: Alternatively, the word is an amalgam of the Greek prefix "hypo-", meaning "under", and the verb "krinein", meaning "to sift or decide". Thus the original meaning implied a deficiency in the ability to sift or decide. This deficiency, as it pertains to one's own beliefs and feelings, informs the word's contemporary meaning.


title: Hypocrisy

text: Whereas "hypokrisis" applied to any sort of public performance (including the art of rhetoric), "hypokrites" was a technical term for a stage actor and was not considered an appropriate role for a public figure. In Athens during the 4th century BC, for example, the great orator Demosthenes ridiculed his rival Aeschines, who had been a successful actor before taking up politics, as a "hypocrites" whose skill at impersonating characters on stage made him an untrustworthy politician. This negative view of the "hypokrites," perhaps combined with the Roman disdain for actors, later shaded into the originally neutral "hypokrisis." It is this later sense of "hypokrisis" as "play-acting", i.e., the assumption of a counterfeit persona, that gives the modern word "hypocrisy" its negative connotation.


title: Hypocrisy

text: Hypocrisy became a major topic in English political history in the early 18th century. The Toleration Act of 1689 allowed for certain rights, but it left Protestant nonconformists (such as Congregationalists and Baptists) deprived of important rights, including that of office-holding. Nonconformists who wanted office ostentatiously took the Anglican sacrament once a year in order to avoid the restrictions. High Church Anglicans were outraged and outlawed what they called "occasional conformity" in 1711 with the Occasional Conformity Act 1711. In the political controversies using sermons, speeches, and pamphlet wars, both high churchmen and Nonconformists attacked their opponents as insincere and hypocritical, as well as dangerously zealous, in contrast to their own moderation.


title: Hypocrisy

text: In his famous book "Fable of the Bees" (1714) English author Bernard Mandeville (1670–1733) explored the nature of hypocrisy in contemporary European society. On the one hand Mandeville was a ‘moralist’ heir to the French Augustinianism of the previous century, viewing sociability as a mere mask for vanity and pride. On the other he was a ‘materialist’ who helped found modern economics. He tried to demonstrate the universality of human appetites for corporeal pleasures. He argued that the efforts of self-seeking entrepreneurs are the basis of emerging commercial and industrial society, a line of thought that influenced Adam Smith (1723–1790) and 19th century utilitarianism. The tension between these two approaches modes ambivalences and contradictions—concerning the relative power of norms and interests, the relationship between motives and behaviours, and the historical variability of human cultures. In the Enlightenment of the 18th century, discussions of hypocrisy were common in the works of Voltaire, Rousseau, and Montaigne.


title: Hypocrisy

text: In the 1750 to 1850 era, Whig aristocrats in England boasted of their special benevolence for the common people. They claimed to be guiding and counseling reform initiatives to prevent the outbreaks of popular discontent that caused instability and revolution across Europe. However Tory and radical critics accused the Whigs of hypocrisy—alleging they were deliberately using the slogans of reform and democracy to boost themselves into power while preserving their precious aristocratic exclusiveness.


title: Hypocrisy

text: Meanwhile, a steady stream of observers from the Continent commented on the English political culture. Liberal and radical observers noted the servility of the English lower classes, the obsession everyone had with rank and title, the extravagance of the aristocracy, a supposed anti-intellectualism, and a pervasive hypocrisy that extended into such areas as social reform.


title: Hypocrisy

text: In the propaganda battles of World War II, Japan attacked American hypocrisy by emphasizing the injustice of the incarceration camps for Japanese in the United States. Radio Tokyo emphasized that the camps revealed the hypocritical American claim to democratic ideals and fair play. The propaganda quoted American founding fathers, neutral sources, and dissenting opinions from major American newspapers. Radio Tokyo utilized fictitious sources as well. It proclaimed the moral superiority of Japan while threatening to mistreat American POWs in retaliation.


title: Hypocrisy

text: American historian Martin Jay in "The Virtues of Mendacity: On Lying in Politics" (2012) explores how writers over the centuries have treated hypocrisy, deception, flattery, lying and cheating, slander, false pretenses, living on borrowed glory, masquerading, conventions of concealment, playacting before others and the arts of dissimulation. He assumes that politics is worthwhile, but since it is unavoidably linked to lying and hypocrisy, Jay concludes that lying must not be all that bad.


title: Hypocrisy

text: In Islam, Quranic Chapter 63 is often titled "The Hypocrites" Hypocrisy is viewed as a serious sickness. The Qur'an rails against those who claim to be believers and peacemakers, thinking they are fooling God and others, but only fool themselves.


title: Hypocrisy

text: In some translations of the Book of Job, the Hebrew word "chaneph" is rendered as "hypocrite", though it usually means "godless" or "profane". In the Christian Bible, Jesus condemns the scribes and Pharisees as hypocrites in the passage known as the Woes of the Pharisees.


title: Hypocrisy

text: In the Buddhist text Dhammapada, Gautama Buddha condemns a man who takes the appearance of an ascetic but is full of passions within.


title: Hypocrisy

text: In Switzerland Carl Jung (1875–1961) attributed hypocrisy to those who are not aware of the dark or shadow-side of their nature. Jung wrote:


title: Hypocrisy

text: It is under all circumstances an advantage to be in full possession of one's personality, otherwise the repressed elements will only crop up as a hindrance elsewhere, not just at some unimportant point, but at the very spot where we are most sensitive. If people can be educated to see the shadow-side of their nature clearly, it may be hoped that they will also learn to understand and love their fellow men better. A little less hypocrisy and a little more self-knowledge can only have good results in respect for our neighbor; for we are all too prone to transfer to our fellows the injustice and violence we inflict upon our own natures.


title: Hypocrisy

text: In "New Paths in Psychology" Jung pointedly referred to the "hypocritical pretenses of man". "Dream-analysis above all else mercilessly uncovers the lying morality and hypocritical pretences of man, showing him, for once, the other side of his character in the most vivid light". Jung omitted this characterization from his later essay "On the Psychology of the Unconscious", which developed out of the former.


title: Hypocrisy

text: Niccolò Machiavelli noted that "the mass of mankind accept what "seems" as what "is"; nay, are often touched more nearly by appearances than by realities". Natural selection works by the principle of survival of the fittest, and several researchers have shown that humans evolved to play the game of life in a Machiavellian way. The best way to cultivate a reputation for fairness is to really be fair. But since it is much harder to "be" fair than to "seem" fair, and since laziness is built deep into human nature, humans more often choose appearance over reality.


title: Hypocrisy

text: "So convenient a thing is it to be a reasonable creature, since it enables one to find or make a reason for everything one has a mind to do." Benjamin Franklin's observation has been confirmed by recent studies in self-deception. In everyday reasoning, humans do little to get real evidence when taking positions or making decisions, and do even less to get evidence for opposing positions. Instead, they tend to fabricate "pseudo-evidence" – often "after" the decision had already been made ("post hoc fabrication").


title: Hypocrisy

text: Humans take a position, look for evidence that supports it, then, if they find "some" evidence – enough so that the position "makes sense" – they stop thinking altogether (the "makes-sense stopping rule"). And, when pressed to produce real evidence, they tend to seek and interpret "evidence" that confirms what they already believe (the "confirmation bias").


title: Hypocrisy

text: Moreover, humans tend to think highly of themselves, highlighting strengths and achievements, and overlooking weakness and failures (the "self-serving bias"). When asked to rate themselves on virtues, skills, or other desirable traits (including ethics, intelligence, driving ability, and sexual skills), a large majority say they are above average. Power and privilege magnify the distortion: 94% of college professors think that they do above average work. This effect is weaker in Asian countries and in other cultures which value the group more highly than the self.


title: Hypocrisy

text: Evolutionary psychologist Robert Kurzban argues that one's moral modules lead one to condemn infidelity while mating modules induce one to commit it.


title: Hypocrisy

text: Robert Wright wrote that "Human beings are a species splendid in their array of moral equipment, tragic in their propensity to misuse it, and pathetic in their constitutional ignorance of the misuse." Humans are very good at challenging the beliefs of other people, but when it comes to their own beliefs, they tend to protect them, not challenge them. A consistent finding of psychological research is that humans are fairly accurate in their perceptions of others, but generally inaccurate in their perceptions of themselves. Humans tend to judge others by their behavior, but think they have special information about themselves – that they know what they are "really like" inside – and thus effortlessly find ways to explain away selfish acts, and maintain the illusion that they are better than others.


title: Hypocrisy

text: Social psychologists have generally viewed hypocrisy as an instantiation of attitudinal and/or behavioral inconsistency. Accordingly, many social psychologists have focused on the role of dissonance in explaining individuals' aversion to hypocritical thinking and behavior. Individuals are motivated to avoid hypocritical stances in order to forestall the negative drive state of dissonance. For example, a dissonance-based study on the use of condoms among young adults showed that induced hypocrisy can lead to increased purchase and use of condoms.


title: Hypocrisy

text: Alternatively, some social psychologists have suggested that individuals view hypocrisy negatively because it suggests that hypocrites are providing a false signal regarding their moral goodness.


title: Hypocrisy

text: Hypocrisy has been an intermittent topic of interest to philosophers since at least Machiavelli. Philosophical issues raised by hypocrisy can be broadly divided into two kinds: metaphysical/conceptual and ethical. Most philosophical commentary on hypocrisy is concerned with the ethical questions it raises: is hypocrisy morally wrong or bad? If it is, is there anything distinctly objectionable about it, or can it be easily subsumed under a broader category of morally objectionable conduct–for example, deceit? Is hypocrisy necessary or desirable for the sake of certain valuable activities–most notably, politics?


title: Hypocrisy

text: Recently, hypocrisy has emerged as a key focus in philosophical discussions of the ethics of blame. It seems that even if a person has violated some moral norm and is genuinely blameworthy for doing so, it is open to them to challenge the blame leveled at them on the grounds that it is hypocritical; a typical expression of this idea is the phrase, "You have no right to blame me!" Accordingly, some philosophers argue that in order to have the standing or entitlement to blame others, one's blame must not be hypocritical. Defenses of this position have usually focused on the connection between hypocrisy and fairness: the basic idea is that the hypocritical blamer in some way fails to treat the target of her blame as a moral equal. Other proposed explanations include the idea that standing in a moral community requires a reciprocal willingness to accept blame, a willingness that hypocrites lack. Patrick Todd argues that all and only those who are committed to the relevant norms possess the standing to blame, and hypocrites lack commitment in the relevant sense. Other philosophers reject the "No-hypocrisy" condition on standing altogether. Typically, these philosophers do not deny that sometimes the wrongness of hypocrisy can outweigh a would-be blamer's entitlement to blame others; but they will insist that this is not invariably the case, and some hypocrites do have standing to blame. R.A. Duff suggests that underlying the disagreement between these two views is a disagreement about the size and scope of moral community, while Kyle Fritz and Daniel Miller suggest that the rejection of the "No-hypocrisy" condition reflects a failure to distinguish between the right to blame and the value of blaming.


title: Hypocrisy

text: The definition of hypocrisy itself is the fundamental question of the relatively new philosophical discussions on hypocrisy. Early answers tended to focus on the deceptive or inconsistent qualities of hypocrisy. For Eva Kittay, for example, the fundamental attribute of hypocrites is "self-referential deception," and for Gilbert Ryle, to be hypocritical is to "try to appear activated by a motive other than one's real motive." On Dan Turner's view, by contrast, the fundamental feature is "conflict or disparity" between a person's attitudes, where this may or may not involve deception. Bela Szabados and Daniel Statman argue that self-deception is the characteristic attribute of "garden variety of hypocrisies." Roger Crisp and Christopher Cowten identify four types of hypocrisy: pretense of moral goodness, moral criticism of others by those possessing faults of their own, failure to satisfy self-acknowledged moral requirements, and a complacent, unreflective commitment to virtues feigned or preached. What unifies these types is a "metavice," a lack of "moral seriousness." More recently, some philosophers–notably, Benjamin Rossi and Fritz and Miller–have defined hypocrisy in terms of dispositions to blame others or to avow commitment to certain norms together with an unwillingness to accept blame from others or to blame themselves. Rossi's "Commitment Account of Hypocrisy" addresses paradigmatic cases of hypocrisy that Fritz and Miller's "Differential Blaming Disposition Account" does not include.


title: Hypocrisy

text: Although there are many negatives to hypocrisy, there can be benefits from it as well. There are also benefits from ignoring it. Political theorist Judith N. Shklar argues, in "Let Us Not Be Hypocritical," we are all too eager to construe even minor deviations from our opponents' professed beliefs as hypocrisy, rather than understandable imperfections and weaknesses to which everyone is prone.


title: Hypocrisy

text: Political journalist Michael Gerson notes that, "There is often hypocritical deception involved in political and diplomatic negotiations, which generally start with principled, nonnegotiable demands that are negotiated away in the process of finding a compromise." Gerson concludes:


title: Hypocrisy

text: hypocrisy is unavoidable and necessary. If people were required, at all times, to live up to ideals of honesty, loyalty and compassion in order for those ideals to exist, there would be no ideals. Being a moral person is a struggle in which everyone repeatedly fails, becoming a hypocrite in each of those moments. A just and peaceful society depends on hypocrites who ultimately refused to abandon the ideals they betray.


title: Green's theorem

text: In vector calculus, Green's theorem relates a line integral around a simple closed curve to a double integral over the plane region bounded by . It is the two-dimensional special case of Stokes' theorem.


title: Green's theorem

text: Let be a positively oriented, piecewise smooth, simple closed curve in a plane, and let be the region bounded by . If and are functions of defined on an open region containing and have continuous partial derivatives there, then


title: Green's theorem

text: In physics, Green's theorem finds many applications. One is solving two-dimensional flow integrals, stating that the sum of fluid outflowing from a volume is equal to the total outflow summed about an enclosing area. In plane geometry, and in particular, area surveying, Green's theorem can be used to determine the area and centroid of plane figures solely by integrating over the perimeter.


title: Green's theorem

text: The following is a proof of half of the theorem for the simplified area "D", a type I region where "C" and "C" are curves connected by vertical lines (possibly of zero length). A similar proof exists for the other half of the theorem when "D" is a type II region where "C" and "C" are curves connected by horizontal lines (again, possibly of zero length). Putting these two parts together, the theorem is thus proven for regions of type III (defined as regions which are both type I and type II). The general case can then be deduced from this special case by decomposing "D" into a set of type III regions.


title: Green's theorem

text: are true, then Green's theorem follows immediately for the region D. We can prove () easily for regions of type I, and () for regions of type II. Green's theorem then follows for regions of type III.


title: Green's theorem

text: Now compute the line integral in (). "C" can be rewritten as the union of four curves: "C", "C", "C", "C".


title: Green's theorem

text: The integral over "C" is negated because it goes in the negative direction from "b" to "a", as "C" is oriented positively (anticlockwise). On "C" and "C", "x" remains constant, meaning


title: Green's theorem

text: Combining () with (), we get () for regions of type I. A similar treatment yields () for regions of type II. Putting the two together, we get the result for regions of type III.


title: Green's theorem

text: Proof of Theorem. Let formula_6 be an arbitrary positive real number. By continuity of formula_7, formula_8 and compactness of formula_9, given formula_10, there exists formula_11 such that whenever two points of formula_9 are less than formula_13 apart, their images under formula_14 are less than formula_6 apart. For this formula_16, consider the decomposition given by the previous Lemma. We have


title: Green's theorem

text: For each formula_19, the curve formula_20 is a positively oriented square, for which Green's formula holds. Hence


title: Green's theorem

text: Every point of a border region is at a distance no greater than formula_13 from formula_23. Thus, if formula_24 is the union of all border regions, then formula_25; hence formula_26, by Lemma 2. Notice that


title: Green's theorem

text: The remark in the beginning of this proof implies that the oscillations of formula_7 and formula_8 on every border region is at most formula_6. We have


title: Green's theorem

text: The hypothesis of the last theorem are not the only ones under which Green's formula is true. Another common set of conditions is the following:


title: Green's theorem

text: The functions formula_39 are still assumed to be continuous. However, we now require them to be Fréchet-differentiable at every point of formula_40. This implies the existence of all directional derivatives, in particular formula_41, where, as usual, formula_42 is the canonical ordered basis of formula_43. In addition, we require the function formula_44 to be Riemann-integrable over formula_40.


title: Green's theorem

text: Suppose formula_52 and formula_53 are continuous functions whose restriction to formula_54 is Fréchet-differentiable. If the function


title: Green's theorem

text: Green's theorem is a special case of the Kelvin–Stokes theorem, when applied to a region in the formula_58-plane.


title: Green's theorem

text: We can augment the two-dimensional field into a three-dimensional field with a "z" component that is always 0. Write F for the vector-valued function formula_59. Start with the left side of Green's theorem:


title: Green's theorem

text: The surface formula_62 is just the region in the plane formula_54, with the unit normal formula_64 defined (by convention) to have a positive z component in order to match the "positive orientation" definitions for both theorems.


title: Green's theorem

text: Green's theorem is also a straightforward result of the general Stokes' theorem using differential forms and exterior derivatives:


title: Green's theorem

text: Considering only two-dimensional vector fields, Green's theorem is equivalent to the two-dimensional version of the divergence theorem:


title: Green's theorem

text: where formula_68 is the divergence on the two-dimensional vector field formula_69, and formula_64 is the outward-pointing unit normal vector on the boundary.


title: Green's theorem

text: To see this, consider the unit normal formula_64 in the right side of the equation. Since in Green's theorem formula_72 is a vector pointing tangential along the curve, and the curve "C" is the positively oriented (i.e. anticlockwise) curve along the boundary, an outward normal would be a vector which points 90° to the right of this; one choice would be formula_73. The length of this vector is formula_74 So formula_75


title: Green's theorem

text: Applying the two-dimensional divergence theorem with formula_77, we get the right side of Green's theorem:


title: Green's theorem

text: Green's theorem can be used to compute area by line integral. The area of a planar region formula_54 is given by


title: Green's theorem

text: It is named after George Green, who stated a similar result in an 1828 paper titled "An Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism". In 1846, Augustin-Louis Cauchy published a paper stating Green's theorem as the penultimate sentence. This is in fact the first printed version of Green's theorem in the form appearing in modern textbooks. Bernhard Riemann gave the first proof of Green's theorem in his doctoral dissertation on the theory of functions of a complex variable.


title: Berkeley Software Distribution

text: The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley. The term "BSD" commonly refers to its open-source descendants, including FreeBSD, OpenBSD, NetBSD, and DragonFly BSD.


title: Berkeley Software Distribution

text: BSD was initially called Berkeley Unix because it was based on the source code of the original Unix developed at Bell Labs. In the 1980s, BSD was widely adopted by workstation vendors in the form of proprietary Unix variants such as DEC Ultrix and Sun Microsystems SunOS due to its permissive licensing and familiarity to many technology company founders and engineers.


title: Berkeley Software Distribution

text: Although these proprietary BSD derivatives were largely superseded in the 1990s by UNIX SVR4 and OSF/1, later releases provided the basis for several open-source operating systems including FreeBSD, OpenBSD, NetBSD, DragonFly BSD, Darwin, and TrueOS. These, in turn, have been used by proprietary operating systems, including Apple's macOS and iOS, which derived from them, and Microsoft Windows, which used (at least) part of its TCP/IP code, which was legal. Code from FreeBSD was also used to create the operating system for the PlayStation 4, PlayStation 3, PlayStation Vita, and Nintendo Switch.


title: Berkeley Software Distribution

text: The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the operating system, allowing researchers at universities to modify and extend Unix. The operating system arrived at Berkeley in 1974, at the request of computer science professor Bob Fabry who had been on the program committee for the Symposium on Operating Systems Principles where Unix was first presented. A PDP-11/45 was bought to run the system, but for budgetary reasons, this machine was shared with the mathematics and statistics groups at Berkeley, who used RSTS, so that Unix only ran on the machine eight hours per day (sometimes during the day, sometimes during the night). A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project. Understanding BSD requires delving far back into the history of Unix, the operating system first released by AT&T Bell Labs in 1969. BSD began life as a variant of Unix that programmers at the University of California at Berkeley, initially led by Bill Joy, began developing in the late 1970s.


title: Berkeley Software Distribution

text: At first, BSD was not a clone of Unix, or even a substantially different version of it. It just included some extra features, which were intertwined with code owned by AT&T.


title: Berkeley Software Distribution

text: In 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor. He helped to install Version 6 Unix and started working on a Pascal implementation for the system. Graduate students Chuck Haley and Bill Joy improved Thompson's Pascal and implemented an improved text editor, ex. Other universities became interested in the software at Berkeley, and so in 1977 Joy started compiling the first Berkeley Software Distribution (1BSD), which was released on March 9, 1978. 1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out.


title: Berkeley Software Distribution

text: The second Berkeley Software Distribution (2BSD), released in May 1979, included updated versions of the 1BSD software as well as two new programs by Joy that persist on Unix systems to this day: the vi text editor (a visual version of ex) and the C shell. Some 75 copies of 2BSD were sent out by Bill Joy.


title: Berkeley Software Distribution

text: A VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAX's virtual memory capabilities. The kernel of 32V was largely rewritten to include Berkeley graduate student Özalp Babaoğlu's virtual memory implementation, and a complete operating system including the new kernel, ports of the 2BSD utilities to the VAX, and the utilities from 32V was released as 3BSD at the end of 1979. 3BSD was also alternatively called Virtual VAX/UNIX or VMUNIX (for Virtual Memory Unix), and BSD kernel images were normally called codice_1 until 4.4BSD.


title: Berkeley Software Distribution

text: After 4.3BSD was released in June 1986, it was determined that BSD would move away from the aging VAX platform. The Power 6/32 platform (codenamed "Tahoe") developed by Computer Consoles Inc. seemed promising at the time, but was abandoned by its developers shortly thereafter. Nonetheless, the 4.3BSD-Tahoe port (June 1988) proved valuable, as it led to a separation of machine-dependent and machine-independent code in BSD which would improve the system's future portability.


title: Berkeley Software Distribution

text: In addition to portability, the CSRG worked on an implementation of the OSI network protocol stack, improvements to the kernel virtual memory system and (with Van Jacobson of LBL) new TCP/IP algorithms to accommodate the growth of the Internet.


title: Berkeley Software Distribution

text: Until then, all versions of BSD used proprietary AT&T Unix code, and were therefore subject to an AT&T software license. Source code licenses had become very expensive and several outside parties had expressed interest in a separate release of the networking code, which had been developed entirely outside AT&T and would not be subject to the licensing requirement. This led to Networking Release 1 (Net/1), which was made available to non-licensees of AT&T code and was freely redistributable under the terms of the BSD license. It was released in June 1989.


title: Berkeley Software Distribution

text: After Net/1, BSD developer Keith Bostic proposed that more non-AT&T sections of the BSD system be released under the same license as Net/1. To this end, he started a project to reimplement most of the standard Unix utilities without using the AT&T code. Within eighteen months, all of the AT&T utilities had been replaced, and it was determined that only a few AT&T files remained in the kernel. These files were removed, and the result was the June 1991 release of Networking Release 2 (Net/2), a nearly complete operating system that was freely distributable.


title: Berkeley Software Distribution

text: Net/2 was the basis for two separate ports of BSD to the Intel 80386 architecture: the free 386BSD by William Jolitz and the proprietary BSD/386 (later renamed BSD/OS) by Berkeley Software Design (BSDi). 386BSD itself was short-lived, but became the initial code base of the NetBSD and FreeBSD projects that were started shortly thereafter.


title: Berkeley Software Distribution

text: BSDi soon found itself in legal trouble with AT&T's Unix System Laboratories (USL) subsidiary, then the owners of the System V copyright and the Unix trademark. The "USL v. BSDi" lawsuit was filed in 1992 and led to an injunction on the distribution of Net/2 until the validity of USL's copyright claims on the source could be determined. The lawsuit slowed development of the free-software descendants of BSD for nearly two years while their legal status was in question, and as a result systems based on the Linux kernel, which did not have such legal ambiguity, gained greater support. The lawsuit was settled in January 1994, largely in Berkeley's favor. Of the 18,000 files in the Berkeley distribution, only three had to be removed and 70 modified to show USL copyright notices. A further condition of the settlement was that USL would not file further lawsuits against users and distributors of the Berkeley-owned code in the upcoming 4.4BSD release.


title: Berkeley Software Distribution

text: The final release from Berkeley was 1995's 4.4BSD-Lite Release 2, after which the CSRG was dissolved and development of BSD at Berkeley ceased. Since then, several variants based directly or indirectly on 4.4BSD-Lite (such as FreeBSD, NetBSD, OpenBSD and DragonFly BSD) have been maintained.


title: Berkeley Software Distribution

text: The permissive nature of the BSD license has allowed many other operating systems, both open-source and proprietary, to incorporate BSD source code. For example, Microsoft Windows used BSD code in its implementation of TCP/IP and bundles recompiled versions of BSD's command-line networking tools since Windows 2000. Darwin, the basis for Apple's macOS and iOS, is based on 4.4BSD-Lite2 and FreeBSD. Various commercial Unix operating systems, such as Solaris, also incorporate BSD code.


title: Berkeley Software Distribution

text: Starting with the 8th Edition, versions of Research Unix at Bell Labs had a close relationship to BSD. This began when 4.1cBSD for the VAX was used as the basis for Research Unix 8th Edition. This continued in subsequent versions, such as the 9th Edition, which incorporated source code and improvements from 4.3BSD. The result was that these later versions of Research Unix were closer to BSD than they were to System V. In a Usenet posting from 2000, Dennis Ritchie described this relationship between BSD and Research Unix:


title: Berkeley Software Distribution

text: Eric S. Raymond summarizes the longstanding relationship between System V and BSD, stating, "The divide was roughly between longhairs and shorthairs; programmers and technical people tended to line up with Berkeley and BSD, more business-oriented types with AT&T and System V."


title: Berkeley Software Distribution

text: In 1989, David A. Curry wrote about the differences between BSD and System V. He characterized System V as being often regarded as the "standard Unix." However, he described BSD as more popular among university and government computer centers, due to its advanced features and performance:


title: Berkeley Software Distribution

text: Berkeley's Unix was the first Unix to include libraries supporting the Internet Protocol stacks: "Berkeley sockets". A Unix implementation of IP's predecessor, the ARPAnet's NCP, with FTP and Telnet clients, had been produced at the University of Illinois in 1975, and was available at Berkeley. However, the memory scarcity on the PDP-11 forced a complicated design and performance problems.


title: Berkeley Software Distribution

text: By integrating sockets with the Unix operating system's file descriptors, it became almost as easy to read and write data across a network as it was to access a disk. The AT&T laboratory eventually released their own STREAMS library, which incorporated much of the same functionality in a software stack with a different architecture, but the wide distribution of the existing sockets library reduced the impact of the new API. Early versions of BSD were used to form Sun Microsystems' SunOS, founding the first wave of popular Unix workstations.


title: Berkeley Software Distribution

text: Some BSD operating systems can run native software of several other operating systems on the same architecture, using a binary compatibility layer. This is much simpler and faster than emulation; for example, it allows applications intended for Linux to be run at effectively full speed. This makes BSDs not only suitable for server environments, but also for workstation ones, given the increasing availability of commercial or closed-source software for Linux only. This also allows administrators to migrate legacy commercial applications, which may have only supported commercial Unix variants, to a more modern operating system, retaining the functionality of such applications until they can be replaced by a better alternative.


title: Berkeley Software Distribution

text: Current BSD operating system variants support many of the common IEEE, ANSI, ISO, and POSIX standards, while retaining most of the traditional BSD behavior. Like AT&T Unix, the BSD kernel is monolithic, meaning that device drivers in the kernel run in privileged mode, as part of the core of the operating system.


title: Berkeley Software Distribution

text: Several operating systems are based on BSD, including FreeBSD, OpenBSD, NetBSD, MidnightBSD, MirOS BSD, GhostBSD, Darwin and DragonFly BSD. Both NetBSD and FreeBSD were created in 1993. They were initially derived from 386BSD (also known as "Jolix"), and merged the 4.4BSD-Lite source code in 1994. OpenBSD was forked from NetBSD in 1995, and DragonFly BSD was forked from FreeBSD in 2003.


title: Berkeley Software Distribution

text: BSD was also used as the basis for several proprietary versions of Unix, such as Sun's SunOS, Sequent's DYNIX, NeXT's NeXTSTEP, DEC's Ultrix and OSF/1 AXP (now Tru64 UNIX). NeXTSTEP later became the foundation for Apple Inc.'s macOS.


title: Sex-determination system

text: A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes.


title: Sex-determination system

text: In some species there are hermaphrodites. There are also some species that are only one sex due to parthenogenesis, the act of a female reproducing without fertilization.


title: Sex-determination system

text: In some species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology. In animals this is often accompanied by chromosomal differences, generally through combinations of XY, ZW, XO, ZO chromosomes, or haplodiploidy. The sexual differentiation is generally triggered by a main gene (a "sex locus"), with a multitude of other genes following in a domino effect.


title: Sex-determination system

text: In other cases, sex of a fetus is determined by environmental variables (such as temperature). The details of some sex-determination systems are not yet fully understood. Hopes for future fetal biological system analysis include complete-reproduction-system initialized signals that can be measured during pregnancies to more accurately determine whether a determined sex of a fetus is male, or female. Such analysis of biological systems could also signal whether the fetus is hermaphrodite, which includes total or partial of both male and female reproduction organs.


title: Sex-determination system

text: Some species such as various plants and fish do not have a fixed sex, and instead go through life cycles and change sex based on genetic cues during corresponding life stages of their type. This could be due to environmental factors such as seasons and temperature. In some gonochoric species, a few individuals may have sex characteristics of both sexes, a condition called intersex.


title: Sex-determination system

text: While diversity in sex determination systems is common throughout the diversity of biology, the systems beyond XY/XX/XO in mammals are often characterized as less common or abnormal, because of the social influence of centering certain human cultural norms when researching sex determination. As such, general biology courses often focus on the simplified genetics of this one system, harmfully excluding people and other organisms from what most people learn in their biology courses.


title: Sex-determination system

text: The XX/XY sex-determination system is the most familiar, as it is found in humans. The XX/XY system is found in most other mammals, as well as some insects. In this system, most females have two of the same kind of sex chromosome (XX), while most males have two distinct sex chromosomes (XY). The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes (autosomes), and are sometimes called allosomes. In some species, such as humans, organisms remain sex indifferent for a time after they're created; in others, however, such as fruit flies, sexual differentiation occurs as soon as the egg is fertilized.


title: Sex-determination system

text: Some species (including humans) have a gene SRY on the Y chromosome that determines maleness. Members of SRY-reliant species can have uncommon XY chromosomal combinations such as XXY and still live.


title: Sex-determination system

text: Human sex is determined by the presence or absence of a Y chromosome with a functional SRY gene. Once the SRY gene is activated, cells create testosterone and anti-müllerian hormone which typically ensures the development of a single, male reproductive system. In typical XX embryos, cells secrete estrogen, which drives the body toward the female pathway.


title: Sex-determination system

text: In Y-centered sex determination, the SRY gene is the main gene in determining male characteristics, but multiple genes are required to develop testes. In XY mice, lack of the gene DAX1 on the X chromosome results in sterility, but in humans it causes adrenal hypoplasia congenita. However, when an extra DAX1 gene is placed on the X chromosome, the result is a female, despite the existence of SRY. Even when there are normal sex chromosomes in XX females, duplication or expression of SOX9 causes testes to develop. Gradual sex reversal in developed mice can also occur when the gene FOXL2 is removed from females. Even though the gene DMRT1 is used by birds as their sex locus, species who have XY chromosomes also rely upon DMRT1, contained on chromosome 9, for sexual differentiation at some point in their formation.


title: Sex-determination system

text: Some species, such as fruit flies, use the presence of two X chromosomes to determine femaleness. Species that use the number of Xs to determine sex are nonviable with an extra X chromosome.


title: Sex-determination system

text: Some fish have variants of the XY sex-determination system, as well as the regular system. For example, while having an XY format, "Xiphophorus nezahualcoyotl" and "X. milleri" also have a second Y chromosome, known as Y', that creates XY' females and YY' males.


title: Sex-determination system

text: At least one monotreme, the platypus, presents a particular sex determination scheme that in some ways resembles that of the ZW sex chromosomes of birds and lacks the SRY gene. The platypus has ten sex chromosomes; males have an XYXYXYXYXY pattern while females have ten X chromosomes. Although it is an XY system, the platypus' sex chromosomes share no homologues with eutherian sex chromosomes. Instead, homologues with eutherian sex chromosomes lie on the platypus chromosome 6, which means that the eutherian sex chromosomes were autosomes at the time that the monotremes diverged from the therian mammals (marsupials and eutherian mammals). However, homologues to the avian DMRT1 gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination. More research must be conducted in order to determine the exact sex determining gene of the platypus.


title: Sex-determination system

text: In this variant of the XY system, females have two copies of the sex chromosome (XX) but males have only one (X0). The "0" denotes the absence of a second sex chromosome. Generally in this method, the sex is determined by amount of genes expressed across the two chromosomes. This system is observed in a number of insects, including the grasshoppers and crickets of order Orthoptera and in cockroaches (order Blattodea). A small number of mammals also lack a Y chromosome. These include the Amami spiny rat ("Tokudaia osimensis") and the Tokunoshima spiny rat ("Tokudaia tokunoshimensis") and "Sorex araneus", a shrew species. Transcaucasian mole voles ("Ellobius lutescens") also have a form of XO determination, in which both sexes lack a second sex chromosome. The mechanism of sex determination is not yet understood.


title: Sex-determination system

text: The nematode "C. elegans" is male with one sex chromosome (X0); with a pair of chromosomes (XX) it is a hermaphrodite. Its main sex gene is XOL, which encodes XOL-1 and also controls the expression of the genes TRA-2 and HER-1. These genes reduce male gene activation and increase it, respectively.


title: Sex-determination system

text: The ZW sex-determination system is found in birds, some reptiles, and some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ). In the chicken, this was found to be dependent on the expression of DMRT1. In birds, the genes FET1 and ASW are found on the W chromosome for females, similar to how the Y chromosome contains SRY. However, not all species depend upon the W for their sex. For example, there are moths and butterflies that are ZW, but some have been found female with ZO, as well as female with ZZW. Also, while mammals deactivate one of their extra X chromosomes when female, it appears that in the case of Lepidoptera, the males produce double the normal amount of enzymes, due to having two Z's. Because the use of ZW sex determination is varied, it is still unknown how exactly most species determine their sex. However, reportedly, the silkworm "Bombyx mori" uses a single female-specific piRNA as the primary determiner of sex. Despite the similarities between the ZW and XY systems, these sex chromosomes evolved separately. In the case of the chicken, their Z chromosome is more similar to humans' autosome 9. The chicken's Z chromosome also seems to be related to the X chromosome of the platypus. When a ZW species, such as the Komodo dragon, reproduces parthenogenetically, usually only males are produced. This is due to the fact that the haploid eggs double their chromosomes, resulting in ZZ or WW. The ZZ become males, but the WW are not viable and are not brought to term.


title: Sex-determination system

text: In both XY and ZW sex determination systems, the sex chromosome carrying the critical factors is often significantly smaller, carrying little more than the genes necessary for triggering the development of a given sex.


title: Sex-determination system

text: The ZZ/Z0 sex-determination system is found in some moths. In these insects there is one sex chromosome, Z. Males have two Z chromosomes, whereas females have one Z. Males are ZZ, while females are Z0.


title: Sex-determination system

text: In some Bryophyte and some algae species, the gametophyte stage of the life cycle, rather than being hermaphrodite, occurs as separate male or female individuals that produce male and female gametes respectively. When meiosis occurs in the sporophyte generation of the life cycle, the sex chromosomes known as U and V assort in spores that carry either the U chromosome and give rise to female gametophytes, or the V chromosome and give rise to male gametophytes.


title: Sex-determination system

text: Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Sex determination is controlled by the zygosity of a complementary sex determiner ("csd") locus. Unfertilized eggs develop into haploid individuals which have a single, hemizygous copy of the "csd" locus and are therefore males. Fertilized eggs develop into diploid individuals which, due to high variability in the "csd" locus, are generally heterozygous females. In rare instances diploid individuals may be homozygous, these develop into sterile males.


title: Sex-determination system

text: The gene acting as a "csd" locus has been identified in the honeybee and several candidate genes have been proposed as a "csd" locus for other Hymenopterans.


title: Sex-determination system

text: Most females in the Hymenoptera order can decide the sex of their offspring by holding received sperm in their spermatheca and either releasing it into their oviduct or not. This allows them to create more workers, depending on the status of the colony.


title: Sex-determination system

text: Other uncommon systems include those of the green swordtail (a polyfactorial system with the sex-determining genes on several chromosomes) the Chironomus midges; the juvenile hermaphroditism of zebrafish, with an unknown trigger; and the platyfish, which has W, X, and Y chromosomes. This allows WY, WX, or XX females and YY or XY males.


title: Sex-determination system

text: Mating type in microorganisms is analogous to sex in multi-cellular organisms, and is sometimes described using those terms, though they are not necessarily correlated with physical body structures. Some species have more than two mating types. "Tetrahymena," a type of ciliate, has seven mating types. "Schizophyllum commune," a type of fungus, has 23,328.


title: Sex-determination system

text: Many other sex-determination systems exist. In some species of reptiles, including alligators, some turtles, and the tuatara, sex is determined by the temperature at which the egg is incubated during a temperature-sensitive period. There are no examples of temperature-dependent sex determination (TSD) in birds. Megapodes had formerly been thought to exhibit this phenomenon, but were found to actually have different temperature-dependent embryo mortality rates for each sex. For some species with TSD, sex determination is achieved by exposure to hotter temperatures resulting in the offspring being one sex and cooler temperatures resulting in the other. This type of TSD is called "Pattern I". For others species using TSD, it is exposure to temperatures on both extremes that results in offspring of one sex, and exposure to moderate temperatures that results in offspring of the opposite sex, called "Pattern II" TSD. The specific temperatures required to produce each sex are known as the female-promoting temperature and the male-promoting temperature. When the temperature stays near the threshold during the temperature sensitive period, the sex ratio is varied between the two sexes. Some species' temperature standards are based on when a particular enzyme is created. These species that rely upon temperature for their sex determination do not have the SRY gene, but have other genes such as DAX1, DMRT1, and SOX9 that are expressed or not expressed depending on the temperature. The sex of some species, such as the Nile tilapia, Australian skink lizard, and Australian dragon lizard, has an initial bias, set by chromosomes, but can later be changed by the temperature of incubation.


title: Sex-determination system

text: It is unknown how exactly temperature-dependent sex determination evolved. It could have evolved through certain sexes being more suited to certain areas that fit the temperature requirements. For example, a warmer area could be more suitable for nesting, so more females are produced to increase the amount that nest next season.


title: Sex-determination system

text: In amniotes, environmental sex determination preceded the genetically determined systems of birds and mammals; it is thought that a temperature-dependent amniote was the common ancestor of amniotes with sex chromosomes.


title: Sex-determination system

text: There are other environmental sex determination systems including location-dependent determination systems as seen in the marine worm "Bonellia viridis" – larvae become males if they make physical contact with a female, and females if they end up on the bare sea floor. This is triggered by the presence of a chemical produced by the females, bonellin. Some species, such as some snails, practice sex change: adults start out male, then become female. In tropical clown fish, the dominant individual in a group becomes female while the other ones are male, and bluehead wrasses ("Thalassoma bifasciatum") are the reverse. Some species, however, have no sex-determination system. Hermaphrodite species include the common earthworm and certain species of snails. A few species of fish, reptiles, and insects reproduce by parthenogenesis and are female altogether. There are some reptiles, such as the boa constrictor and Komodo dragon that can reproduce both sexually and asexually, depending on whether a mate is available.


title: Sex-determination system

text: Chromosomal sex determination may have evolved early in the history of eukaryotes. But in plants it has been suggested to have evolved recently.


title: Sex-determination system

text: The accepted hypothesis of XY and ZW sex chromosome evolution in amniotes is that they evolved at the same time, in two different branches.


title: Sex-determination system

text: No genes are shared between the avian ZW and mammal XY chromosomes and the chicken Z chromosome is similar to the human autosomal chromosome 9, rather than X or Y. This suggests not that the ZW and XY sex-determination systems share an origin but that the sex chromosomes are derived from autosomal chromosomes of the common ancestor of birds and mammals. In the platypus, a monotreme, the X chromosome shares homology with therian mammals, while the X chromosome contains an avian sex-determination gene, further suggesting an evolutionary link.


title: Sex-determination system

text: However, there is some evidence to suggest that there could have been transitions between ZW and XY, such as in "Xiphophorus maculatus", which have both ZW and XY systems in the same population, despite the fact that ZW and XY have different gene locations. A recent theoretical model raises the possibility of both transitions between the XY/XX and ZZ/ZW system and environmental sex determination The platypus' genes also back up the possible evolutionary link between XY and ZW, because they have the DMRT1 gene possessed by birds on their X chromosomes. Regardless, XY and ZW follow a similar route. All sex chromosomes started out as an original autosome of an original amniote that relied upon temperature to determine the sex of offspring. After the mammals separated, the reptile branch further split into Lepidosauria and Archosauromorpha. These two groups both evolved the ZW system separately, as evidenced by the existence of different sex chromosomal locations. In mammals, one of the autosome pair, now Y, mutated its SOX3 gene into the SRY gene, causing that chromosome to designate sex. After this mutation, the SRY-containing chromosome inverted and was no longer completely homologous with its partner. The regions of the X and Y chromosomes that are still homologous to one another are known as the pseudoautosomal region. Once it inverted, the Y chromosome became unable to remedy deleterious mutations, and thus degenerated. There is some concern that the Y chromosome will shrink further and stop functioning in ten million years: but the Y chromosome has been strictly conserved after its initial rapid gene loss.


title: Sex-determination system

text: There are some vertebrate species, such as the medaka fish, that evolved sex chromosomes separately; their Y chromosome never inverted and can still swap genes with the X. These species' sex chromosomes are relatively primitive and unspecialized. Because the Y does not have male-specific genes and can interact with the X, XY and YY females can be formed as well as XX males. Non-inverted Y chromosomes with long histories are found in pythons and emus, each system being more than 120 million years old, suggesting that inversions are not necessarily an eventuality. XO sex determination can evolve from XY sex determination with about 2 million years.


title: Order of magnitude

text: An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic distributions are common in nature and considering the order of magnitude of values sampled from such a distribution can be more intuitive. When the reference value is 10, the order of magnitude can be understood as the number of digits in the base-10 representation of the value. Similarly, if the reference value is one of some powers of 2, since computers store data in a binary format, the magnitude can be understood in terms of the amount of computer memory needed to store that value.


title: Order of magnitude

text: Differences in order of magnitude can be measured on a base-10 logarithmic scale in “decades” (i.e., factors of ten). Examples of numbers of different magnitudes can be found at Orders of magnitude (numbers).


title: Order of magnitude

text: Generally, the order of magnitude of a number is the smallest power of 10 used to represent that number. To work out the order of magnitude of a number formula_1, the number is first expressed in the following form:


title: Order of magnitude

text: where formula_3, or approximately formula_4. Then, formula_5 represents the order of magnitude of the number. The order of magnitude can be any integer. The table below enumerates the order of magnitude of some numbers in light of this definition:


title: Order of magnitude

text: The geometric mean of formula_6 and formula_7 is formula_8, meaning that a value of exactly formula_8 (i.e., formula_10) represents a geometric "halfway point" within the range of possible values of formula_11.


title: Order of magnitude

text: Some use a simpler definition where <math>0.5, perhaps because the arithmetic mean of formula_8 and formula_13 approaches formula_14 for increasing formula_15. This definition has the effect of lowering the values of formula_5 slightly: