Brightness contrast effects in a pupillometric experiment

Pupillometric experiments which employ picture slides as stimuli have been criticized for their failure to control intrastimulus brightness variation. This factor has been suggested as the source of pupil size changes that are observed in response to picture slide stimuli, rather than the emotional response of the subject. The present study required subjects to direct their gaze to areas of a slide that varied in brightness. On the basis of the obtained results, it was concluded that brightness contrast does not play a major role in the pupil's response to picture slide stimuli which have been properly prepared.