Demonstrating specific cognitive deficits: A psychometric perspective

Cognitive deficits associated with psychopathology often do not occur in is olation. Consequently, identifying a specific deficit in a disorder require s comparing the magnitude of group differences on theoretically relevant me asures with those on control tasks measuring other constructs, L. J, Chapma n and J. P. Chapman (1973) noted that common forms of such Group X Task int eractions are theoretically ambiguous unless performance measures have comp arable discriminating power. The principles of psychometric matching for di scriminating power developed in the Chapmans' research program are reviewed , and both criticisms and alternative psychometric approaches are evaluated . Psychometric matching can be mindful of threats to the construct validity of measures and frequently remains methodologically necessary. Otherwise, interactions involving measures that vary in sensitivity to individual diff erences may be misinterpreted as evidence for specific deficits.