Psychological Some laboratory research demonstrates correlations between<unk>  and atypical responses to aversive stimuli, including weak conditioning to painful stimuli and poor learning of avoiding responses that cause punishment, as well as low reactivity in the autonomic nervous system as measured with skin conductance while waiting for a painful stimulus but not when the stimulus occurs. While it has been argued that the reward system functions normally, some studies have also found reduced reactivity to pleasurable stimuli. According to the response modulation hypothesis,<unk> c individuals have also had difficulty switching from an ongoing action despite environmental cues signaling a need to do so. This may explain the difficulty responding to punishment, although it is unclear if it can explain findings such as deficient conditioning. There may be methodological issues regarding the research. While establishing a range of idiosyncrasies on average in linguistic and affective processing under certain conditions, this research program has not confirmed a common pathology of<unk> . Neurological Dysfunction of the orbitofrontal cortex, among other areas, is implicated in the mechanism of<unk> . Thanks to advancing MRI studies, experts are able to visualize specific brain differences and abnormalities of individuals with<unk>  in areas that control emotions, social interactions, ethics, morality, regret, impulsivity and conscience within the brain. Blair, a researcher who pioneered research into<unk> c tendencies stated, "With regard to<unk> , we have clear indications regarding why the pathology gives rise to the emotional and behavioral disturbance and important insights into the neural systems implicated in this pathology". Dadds et al., remarks that despite a rapidly advancing neuroscience of empathy, little is known about the developmental underpinnings of the<unk> c disconnect between affective and cognitive empathy. A 2008 review by Weber et al. suggested that<unk>  is sometimes associated with brain abnormalities in prefrontal-temporo-limbic regions that are involved in emotional and learning processes, among others. Neuroimaging studies have found structural and functional differences between those scoring high and low on the PCL-R in a 2011 review by Skeem et al. stating that they are "most notably in the amygdala, hippocampus and parahippocampal gyri, anterior and posterior cingulate cortex, striatum, insula, and frontal and temporal cortex". A 2010 meta-analysis found that antisocial, violent and<unk> c individuals had reduced structure function in the right orbitofrontal cortex, right anterior cingulate cortex and left dorsolateral prefrontal cortex. The amygdala and frontal areas have been suggested as particularly important. People scoring 25 or higher in the PCL-R, with an associated history of violent behavior, appear on average to have significantly reduced microstructural integrity between the white matter connecting the amygdala and orbitofrontal cortex (such as the uncinate fasciculus). The evidence suggested that the degree of abnormality was significantly related to the degree of<unk>  and may explain the offending behaviors. Furthermore, changes in the amygdala have been associated with "callous-unemotional" traits in children. However, the amygdala has also been associated with positive emotions, and there have been inconsistent results in the studies in particular areas, which may be due to methodological issues. Some of these findings are consistent with other research and theories. For example, in a neuroimaging study of how individuals with<unk>  respond to emotional words, widespread differences in activation patterns have been shown across the temporal lobe when<unk> c criminals were compared to "normal" volunteers, which is consistent with views in clinical psychology. Additionally, the notion of<unk>  being characterized by low fear is consistent with findings of abnormalities in the amygdala, since deficits in aversive conditioning and instrumental learning are thought to result from amygdala dysfunction, potentially compounded by orbitofrontal cortex dysfunction, although the specific reasons are unknown. Considerable research has documented the presence of the two subtypes of primary and secondary<unk> . Proponents of the primary-secondary<unk>  distinction and triarchic model argue that there are neurological differences between these subgroups of<unk>  which support their views. For instance, the boldness factor in the triarchic model is argued to be associated with reduced activity in the amygdala during fearful or aversive stimuli and reduced startle response, while the disinhibition factor is argued to be associated with impairment of frontal lobe tasks. There is evidence that boldness and disinhibition are genetically distinguishable. Biochemical High levels of testosterone combined with low levels of cortisol and/or serotonin have been theorized as contributing factors. Testosterone is "associated with approach-related behavior, reward sensitivity, and fear reduction", and injecting testosterone "shifts the balance from punishment to reward sensitivity", decreases fearfulness, and increases "responding to angry faces". Some studies have found that high testosterone levels are associated with antisocial and aggressive behaviors, yet other research suggests that testosterone alone does not cause aggression but increases dominance-seeking. It is unclear from studies if<unk>  correlates with high testosterone levels, but a few studies have found that disruption of serotonin neurotransmission disrupts cortisol reactivity to a stress-inducing speech task. Thus, dysregulation of serotonin in the brain may contribute to the low cortisol levels observed in<unk> . Cortisol increases withdrawal behavior and sensitivity to punishment and aversive conditioning, which are abnormally low in individuals with<unk>  and may underlie their impaired aversion learning and disinhibited behavior. High testosterone levels combined with low serotonin levels are associated with "impulsive and highly negative reactions", and may increase violent aggression when an individual is provoked or becomes frustrated. Several animal studies note the role of serotonergic functioning in impulsive aggression and antisocial behavior. However, some studies on animal and human subjects have suggested that the emotional-interpersonal traits and predatory aggression of<unk> , in contrast to impulsive and reactive aggression, is related to increased serotoninergic functioning. A study by Dolan and Anderson, regarding the relationship between serotonin and<unk> c traits in a sample of personality disordered offenders, found that serotonin functioning as measured by prolactin response, while inversely associated with impulsive and antisocial traits, were positively correlated with arrogant and deceitful traits, and, to a lesser extent, callous and remorseless traits. Bariş Yildirim theorizes that the 5-HTTLPR "long" allele, which is generally regarded as protective against internalizing disorders, may interact with other serotoninergic genes to create a hyper-regulation and dampening of affective processes that results in<unk> 's emotional impairments. Furthermore, the combination of the 5-HTTLPR long allele and high testosterone levels has been found to result in a reduced response to threat as measured by cortisol reactivity, which mirrors the fear deficits found in those afflicted with<unk> . Studies have suggested other correlations.<unk>  was associated in two studies with an increased ratio of HVA (a dopamine metabolite) to 5-HIAA (a serotonin metabolite). Studies have found that individuals with the traits meeting criteria for<unk>  show a greater dopamine response to potential "rewards" such as monetary promises or taking drugs such as amphetamines. This has been theoretically linked to increased impulsivity. A 2010 British study found that a large 2D:4D digit ratio, an indication of high prenatal estrogen exposure, was a "positive correlate of<unk>  in females, and a positive correlate of callous affect<unk>  sub-scale) in males". Findings have also shown monoamine oxidase A to affect the predictive ability of the PCL-R. Monoamine oxidases (MAOs) are enzymes that are involved in the breakdown of neurotransmitters such as serotonin and dopamine and are, therefore, capable of influencing feelings, mood, and behavior in individuals. Findings suggest that further research is needed in this area.
Psychopathy
Gemütlose psychopathy
Externalizing disorder
Internalizing disorder
Tic disorder
Agoraphobia
Personality pathology
Kleptomania