We need to estimate the amount of explanatory parsimony that might be achievable by postulating particular cognitive defects, each subsuming several surface features. It is possible that performance is impaired on a broad range of tests, however, because the cognitive processes that are defective are not those relying on specific processors but rather the pervasive, nonspecific processes that coordinate and monitor the activity of other processors. However, to establish such a dissociation, several preconditions would have to satisfied. The demonstration would be suspect if either group showed equal abnormality in tests that purport to be sensitive to dysfunction in other brain regions. Moreover, it would also need to be established that patients with lesions restricted to nonfrontal regions perform normally on these tests.
Contrary evidence abounds.
The WCST is sensitive to temporal lobe dysfunction. The lack of any such control measures in Abbruzzese et al. reveals a general failure to design for falsifiability rather than corroboration. Moreover, the fact that the two tests, set in opposition, both purport to yield measures of perseveration is a reminder of the cognitive opacity of such tests. Whereas a true double dissociation would reflect a categorical distinction between processing operations recruited by either test, the obtained pattern of results is at least as likely to reflect variation in one of the pervasive nonspecific requirements of such tests. For example, perfect OAT performance can be obtained with a working memory load extending back a single trial.