Executive functions and task switching

Over the past few decades, the interest in executive functions has been gro wing, both in cognitive psychology and in neuropsychology. Already for some time, neuropsychologists have been trying to gain insight in the origins o f the prefrontal syndrome. The crucial problem they are facing is related t o the validity and reliability of the neuropsychological tests used to asse ss the dysexecutive syndrome (Rabbitt, 1997). Validity is a problem because the syndrome is ill-defined and multifaceted. Executive control is require d in many situations, among others in situations that involve planning and decision making, in situations that involve error correction or trouble sho oting, in situations where well-learned responses are lacking, in dangerous or technically difficult situations and in situations that require the ove rcoming of a strong habitual response or that require resistance to temptat ion (Burgess, 1997, p. 84). Although all these aspects are quite typical of the dysexecutive syndrome, most patients will fail only in some of the sit uations listed. Consequently, a test which is sensitive to a particular def icit (e.g., planning) may be insensitive to other deficits (e.g., inhibitio n). For these reasons, low correlations are expected between tests in a sam ple of prefrontal patients. Moreover, many so-called frontal tests share fe atures with problem-solving and intelligence tests, which leads some schola rs to propose that executive function is nothing but Spearman's g (see e.g. , Sternberg, 1985). Yet there is evidence against this view (e.g., Ardila, Pineda, & Rosselli, 2000; Crinella & Yu, 2000).