the “dynamic developmental” theory of attention-deficit/hyperactivity disorder (adhd) has come full circle from wender's (1971) reinforcement hypothesis. by specifying the principle of time constraints on reinforcement and extinction, the present theory allows for empirical validation. however, the theory implies, but does not discuss, implications for the neurophysiology of comorbidity in adhd. the authors' attribution of comorbid oppositional behavior to parental and societal reinforcement leaves out biological factors.