He would do something horrific and pretend like it was normal and nothing was wrong. (Phineas Gage: A Gruesome but True Story About Brain Science).
In a study conducted by Raines, Venables, and Williams in 1990 it was shown that future criminals had lower skin conductance activity, lower heart rate during rest periods, and more slow-frequency brain wave activity which are signs of low arousal. To offset their low arousal, the people suffering from this disorder, seek stimulation. The arousal that they experience is something that a normal person would seek from talking to friends or watching a movie but instead these people who suffer from this disorder gain it through such horrible acts a lying, cheating, and stealing. (Abnormal Psychology Third Edition (Instructors Edition), pg. 402/The Psychopathology of Crime: Criminal Behavior As a Clinical Disorder, pg. 237 ).
Another theory is labeled the cortical immaturity hypothesis of psychopathy. This theory hypothesizes that the cerebral cortex of psychopaths is at a primitive stage of development. This would explain the behavior of psychopaths often described as child-like. This hypothesis was formulated because, children have an abundance of low frequency theta waves that disappear, as they become adults, but in adult psychopaths it was found that they exhibit these brainwaves also when they are awake. The abundance of low frequency theta waves can be explained simply. Because psychopaths have a lack for not caring, being hooked up to all sorts of equipment and having tests run on them was not an elevating effect. This would make them exhibit high theta waves because theta waves indicate such states as drowsiness and boredom. When a normal person is hooked up to machines and has tests conducted on them you would not see high activity of theta waves because they would be concerned about the procedures and surroundings. (Abnormal Psychology Third Edition (Instructors Edition), pg.