Most psychologists agree that a person's basic personality—whether they are an introvert or extrovert, for example—remains the same throughout life. What we might see as personality changes are actually just responses to external factors, such as getting a job, getting married or becoming a parent. That said, research does indicate that our personalities become more solidified, or stable, as we get older. 
 
 That change is not linear, however. New research indicates that our personalities become increasingly stable as our 20s melt into our 30s, 40s and even 50s, but that that stability then often begins to taper off in old age, Research Digest reports. 
 
 Researchers in New Zealand recruited 4,000 men and women aged 20 to 80 to complete a personality questionnaire twice, with a gap of two years in between. The survey measured a person's honesty-humility factor as well as five major personality traits: extraversion, agreeableness, conscientiousness, neuroticism and openness to experience, Research Digest writes. They compared how people's scores varied between years, and analyzed how all of the participants personalities related to one another, depending on age. 
 
 Most people's personalities were generally stable, they found, but the stability of those trait followed a bell curve over time, peaking at middle-age and then dropping again. For certain traits—conscientiousness, openness to experience, and honesty-humility—Research Digest writes, the oldest participants' personality stability matched those of the youngest. 
 
 Other interesting finds included "domain specific" variations, or ones that seem to be linked to what a person is dealing with at a particular point in their life. People in their 30s, for example, showed high levels of neuroticism, but by the time they reached their 50s that had tapered off and had been replaced by conscientiousness, openness and honesty-humility. ||||| Photo: Nat Fein/Getty Images 
 
 At any given moment, an estimated 108 million people in the United States are on a diet. But despite the fact that the U.S. weight-loss industry makes roughly $20 billion in revenue each year, people continue to fail for one reason or another. Part of the problem, new research suggests, is that our eating habits are influenced by deep-seated personality traits. Your neuroticism, in other words, could be partially responsible for your love of chocolate and cheese. 
 
 For the study, published in the journal Appetite, researchers at the Swiss Federal Institute of Technology sent three questionnaires — one on personality, one on eating habits, and one on food choices — to a random sample of addresses. After excluding subjects who skipped more than 10 percent of the questions, data from nearly a thousand participants (with an average age of 55 years old) was analyzed. 
 
 The personality questions were designed to measure what psychologists believe are the five basic dimensions of personality — openness, conscientiousness, extroversion, agreeableness, and neuroticism. The researchers were curious whether, and to what extent, high or low scores on these different traits would correlate with certain eating habits. 
 
 “We found that a person’s personality does, in fact, determine why he or she eats and what he or she eats,” said Carmen Keller, the study’s lead author. For one thing, “A lack of conscientiousness leads people to eat impulsively and to lose self-control in the face of tempting food situations with palatable and nicely smelling and tasting food,” she explained. In addition, “Neurotic people may eat too much high-caloric food to deal with their negative emotions.” 
 
 Extroversion, which, unlike neuroticism or a lack of conscientiousness tends to have mostly positive connotations in society, was also linked to potentially unhealthy eating habits. “A surprising result is that extroverted people eat more due to external reasons — such as a nice smell or the taste of food — and, in turn, they often consume more meat, sweet foods, savory foods, and sugar-sweetened drinks,” explained Keller. “It might be that the higher sociability of extroverted people results in having more meals with other people and, therefore, eating foods that are not healthy.” Indeed, a lot of past research has suggested that social components greatly influence both what people eat and how frequently they exercise, including studies showing that people-pleasers eat more, women mimic each other’s eating behaviors, and finding a walking group can help you become healthier. 
 
 Taken together, the results reported by Keller and her team suggest that certain personality characteristics can be seen as “risk factors” for an unhealthy lifestyle. “These findings add to a growing body of evidence showing the importance of the personality traits of neuroticism and conscientiousness for a variety of health-related behaviors, including a healthy diet,” said Tim Bogg, an assistant professor of psychology at Wayne State University, who has studied conscientiousness and health, but who wasn’t involved in this study. “The results show that part of the complicated puzzle of maintaining a healthy diet over the long term is related to our general tendencies for emotion regulation and self-control, not simply how good we are at counting calories or avoiding trans fats.” 
 
 In other words, there could be an underrated “know thyself” aspect to successful weight management — understanding how you respond to a stressful day at work, say, or to attending a party where there’s likely to be a lot of food. As Fiona Johnson, a research associate at University College London who also wasn’t affiliated with this study explained, since personality traits are “largely stable over the life course,” understanding the connection between them and eating habits could offer important new opportunities for people to better monitor and control their eating habits. “Overcoming these fundamental tendencies can be very difficult, and identifying ways in which people can boost their capacity to control their eating (eating self-regulation) is the next big challenge in eating research.” 
 
 There are limitations to this study — for example, it only sampled Swiss subjects, and did so with self-reported inventories — but it certainly adds some evidence to the common-sense notion that our personalities, which greatly influence how we react to just about everything, also affect what — and how much — to eat. So while there’s more research to be done, those trying to lose weight might want to look into not just calorie-counting apps and healthier foods at the supermarket, but personality inventories, too.
– There's no doubt about it: The human body goes through major changes in youth and old age. And these biological and social changes may be the reasons behind what researchers are calling less stable personalities at those life stages. In fact, according to a study of almost 4,000 New Zealanders between the ages of 20 and 80, the stability of one's personality increases through youth and into middle age and peaks in our 50s, before we slide back into less stable versions of ourselves, reports Research Digest. As the Smithsonian puts it, "in some ways, our 80-year-old selves mirror our 20-year-old selves." Some traits peaked at different times; the most stable traits in one's 30s are extraversion and neuroticism, while in the late 40s and early 50s it is openness, honesty-humility, and conscientiousness. The only trait that showed "gradually reduced stability" throughout life was agreeableness; apparently we are simply less and less agreeable as we pack the years on. Still, one's most basic personality—introvert vs. extrovert, for example—tends to remain consistent throughout one's life, even if the stability of traits waxes and wanes, notes the Smithsonian. (Other researchers have even calculated the country's most extroverted city.)