Impulsivity and inhibitory control in normal development and childhood psychopathology.

Two experiments investigated the development and pathology of inhibitory control in children. Inhibitory control was investigated with the stop-signal paradigm, which is based on a formal theory of inhibition and directly measures the mechanism of inhibition. The ability to inhibit developed little after Grade 2, but subjects with attention deficit disorder with hyperactivity (ADDH) showed deficient inhibitory control. Their deficient inhibitory control was attributable to the subgroup of ADDH subjects with pervasive hyperactivity who had a more severe inhibitory deficit than did the situational hyperactive subgroup, the normal group, and the pathological controls. These studies reflect the utility of the stop-signal paradigm as a measure of inhibitory control. The concept of inhibitory control is central in theories of child development and in the definition and explanation of psychopathological disorders of childhood—in particular, of attention deficit disorder with hyperactivity (ADDH; Douglas, 1983; Kogan, 1983; Milich Kramer, 1984). Inhibitory control is one of several processes that perform the executive functions