Easier tasks can have better discriminating power: the case of verbal fluency

Loren and Jean Chapman highlighted the importance that the psychometric characteristics of a task may have when comparing different populations (L. J. Chapman & J. P. Chapman, 1973, 1978). Specifically, they pointed out that when comparing 2 tasks measuring different constructs, there is a greater likelihood of finding larger deficits on a task with higher discriminating power, irrespective of what the task measures. While researchers have addressed this issue, they typically have assumed that more difficult tasks have greater discriminating power, often without actually measuring discriminating power. In this article, the authors present data from 2 studies using phonologic and category fluency tasks to demonstrate that the critical factor for task selection and matching is discriminating power, not task difficulty.