A substantial amount of evidence suggests that bilateral damage to the amygdala is associated with fearlessness and in some cases, psychopathic personality traits. Additionally, lesions to this area have been shown to lead to other emotional and behavioral changes. Damage to this area can severely affect personality and decision-making, and as noted, can produce signs

 of psychopathic personality traits. However, it is undetermined as to whether unilateral lesions to the amygdala will have the same influence on these traits compared to bilateral lesions. In order to investigate if unilateral amygdala lesions lead to psychopathic traits, we administered the Psychopathic Personality Inventory-Revised (PPI-R) test to 20 individuals with focal, unilateral lesions to the anterior temporal lobes, including the amygdala. The PPI-R provides comprehensive assessment of various levels of psychopathic traits, e.g., fearlessness, cold-heartedness, and stress immunity. The pattern of results from our study suggests that patients with amygdala lesions were elevated on specific psychopathic traits, such as fearlessness and impulsive nonconformity, but scored normally on other subscales. We conclude that individuals with unilateral amygdala lesions display small but significant elevations on some, but not all, psychopathic traits, implying that amygdala dysfunction may play a role in some aspects of psychopathic personality.