Effects on pupil size of manual and verbal indicators of cognitive task fulfillment

A total of20 Ss attempted to generate images to concrete and abstract stimulus words while pupillary activity was continuously photographed. One group (N =5) was required to press a key when an image occurred, a second to describe the image, and a third to press a key as well as describe the image. No overt indicator was required of a fourth group. Results showed that greater dilation occurred during the imagery task than during a control period only in those conditions in which an overt response indicated task fulfillment. Consistent with earlier findings significantly greater dilation occurred to abstract than concrete stimulus words in the key press condition.