Cognitive processing of uncertainty: Its effect on pupillary dilation and preference ratings

The prediction of greater pupillary dilation as unpredictability (induced by random-turn shapes) increased was supported (p <.001) in studies involving 40 young adults and 10 children. The postulated linearity of this increase found support, except in cases where apparent stimulus-selection strategies attenuated the dilation at higher levels of variability. Those Ss who did preference ratings concomitantly with the intake of visual unpredictability evidenced significantly greater dilation (p <.001) at the time of reporting the rating. Both children and adults dilated significantly less to the shapes after prolonged experience with similar stimuli. indicating development of either ability to handle variability or to selectively filter input, but age was not a factor. The lack of any significant relationship between pupillary dilation and preference indicated the need for more definitive work in determining when these two indices profitably complement each other. Finally, adults dilated more to provocative auditory stimuli than to the visual shapes.