Short answers, pulled from the story.
Psychopathy is a personality construct characterized by impaired empathy and remorse, persistent antisocial behavior, and bold, disinhibited, and egocentric traits, often masked by superficial charm. Psychosis is a separate condition involving hallucinations, delusions, or a marked disconnection from reality. The two are categorically different, though popular media frequently conflates them.
Canadian psychologist Robert D. Hare introduced the Psychopathy Checklist in 1980, building on Hervey Cleckley's criteria from the 1940s and his own research on criminals and incarcerated offenders in Canada. It was revised in 1991 to become the PCL-R and is widely referred to as the "gold standard" for assessing psychopathy.
Research has found differences in the amygdala, hippocampus, anterior and posterior cingulate cortex, striatum, insula, and frontal and temporal cortex in individuals scoring high on the PCL-R. Studies have also found significantly reduced microstructural integrity in the uncinate fasciculus, the white matter connecting the amygdala and the orbitofrontal cortex, in people scoring 25 or higher with a history of violent behavior. An approximate 18% smaller amygdala size has been linked to lower emotional sensation regarding fear and sadness.
Both genetic and environmental factors contribute. A study of children found more than 60% heritability for callous and unemotional traits. A study by Farrington of London males found that the strongest environmental predictors of a high psychopathy score in adulthood included having a convicted parent, physical neglect, low father involvement, and low family income. Proponents of the triarchic model believe psychopathy results from an interaction between genetic predispositions and an adverse environment.
No cure or approved pharmacological therapy exists for the emotional, interpersonal, and moral deficits of psychopathy. The most supported approaches focus on managing antisocial behavior rather than changing core character, including reward-based management in institutional settings and treatments that emphasize the tangible value of prosocial behavior. One study found the antipsychotic clozapine may reduce behavioral dysfunctions in high-security hospital inpatients with antisocial personality disorder and psychopathic traits.
Robert Hare described psychopathy as lacking a sense of empathy or morality, and sociopathy as differing from the average person mainly in the sense of right and wrong. The term sociopathy may have been introduced in 1909 in Germany by Karl Birnbaum and in 1930 in the US by George E. Partridge as an alternative emphasizing social and environmental causes. Hare noted that those who see the causes as primarily social tend to prefer the term sociopathy, while those who believe psychological, biological, and genetic factors are also involved tend to prefer psychopathy.