The purpose of this proposal is to use recent theoretical developments in the neuropsychology and psychophysiology of antisocial personality disorder (psychopathy) in orer to: (a) clarify the importance of situational and motivational variables in predicting the influence of punishment (loss of reward) on the behavior of psychopaths; (b) operationalize a distinctive behavioral style that discriminates between psychopathic and nonpsychopathic offenders, and (c) provide behavioral data that will be essential to the evaluation and interpretation of the emerging physiologically-based theories of psychopathy and other syndromes of disinhibition. Like traditional explanations of the psychopaths' failure to learn from punishment, the neuropsychological model suggests that psychopaths are unresponsive to punishment in some circumstances (e.g., in the absence of incentives). However, the model suggests that psychopaths are hyperresponsive to punishment under conditions of positive incentive. Most importantly, this responsivity to punishment under conditions of "reward" leads to behavioral activation instead of the usual behavioral inhibition. Two sets of experiments are proposed that use behavioral tasks to assess the effects of incentive conditions on behavioral activation and behavioral inhibiton on criminals. In Set A, the effects of punishment on behavior are assessed using response time on a two choice (same-different) pattern matching task. Under punishment-only conditions, psychopaths are expected to respond more slowly than controls; when the task involves reward and punishment, psychopaths are expected to respond very quickly on trials following punishment; and when the task follows a punishment-only pretreatment, psychopaths are expected to appear "over-activated" on the task. In Set B, one experiment investigates the effect of this "paradoxical" response to punishment on the behavioral inhibition of psychopaths engaged in a passive-avoidance task. Another experiment explores the possibility that a tendency to behavioral activation under incentive conditions constitutes a relatively stable behavioral style that could account for the psychopaths' apparent failure to learn from experience, low frustration tolerance, and poor judgement. The health-related implications of this proposal pertain to the identification of a distinctive behavioral style among psychopaths that would further efforts to discover the etiology of psychopathy; provide a meas of identifying this style for the purposes of prevention and comparison with other impulsive populations; and provide a context for the development of more effective preventative or treatment interventions.