Figure 9.8 The Wisconsin Card Sorting Task Subjects start sorting cards by one dimension (color, for instance) then, without notice, they are reinforced for sorting by another dimension (shape, for instance). The number of errors on “switch” trials is a measure of the executive function of switching.

(With permission from E. A. Berg (1948). A simple objective technique for measuring flexibility in thinking. Journal of General Psychology 39:15-22. Copyright © 1948. Reproduced by permission of Taylor & Francis Ltd. http://www.tandf.co.uk/journals and Taylor & Francis LLC http://www.tandfonline.com)