Perception & Psychophysics

, Volume 2, Issue 3, pp 101-105

First online:

Pupillary responses in a pitch-discrimination task

  • Daniel HahnemannAffiliated withCenter for cognitive studies, Harvard University
  • , Jackson BeattyAffiliated withHuman Performance Center, University of Michigan


Pupils were measured while observers made pitch judgments under the method of constant stimuli. A substantial dilation occurs immediately after the presentation of the comparison tone, and the size of this response is closely correlated to the difficulty of the discrimination. Baseline changes occur within each block of trials, but have little effect on the magnitude of dilations. Responses to redundant stimuli, including the standard itself, decrease during the experimental session. The results support the validity of pupillary measurements as an index of processing load.