Dissociations among tasks involving inhibition: a single-case study.
Recent theories of working memory have emphasized the role of inhibition in suppressing irrelevant information. Moreover, psychometric studies have reported that several inhibition tasks with very diverse requirements load on a single inhibition factor. A patient with left inferior frontal damage, Patient M.L., previously reported to have a semantic short-term memory deficit (R. C. Martin & He, 2004), showed evidence of difficulty with inhibition on short-term memory tasks. We investigated whether he would show evidence of inhibition difficulty on two verbal tasks (a Stroop task and a recent-negatives task) and two nonverbal tasks (a nonverbal spatial Stroop task and an antisaccade task). M.L. was impaired on both verbal tasks but performed normally on the nonverbal tasks. M.L.'s data also represent a dissociation between Stroop and antisaccade performance, two tasks that load on a single factor in factor-analytic studies. The implications of these data for theories of inhibition and executive function are discussed.