Susan Galvin

Department of Psychology, University of Otago, Dunedin, New Zealand

Perception Without Awareness

In the busy, modern, human brain, not all machinations are brought into conscious awareness, and it is intriguing to consider which of our sensory processes escape our notice. It has been suggested that if observers can discriminate between a signal and noise (a type I task in the theory of signal detectability) yet cannot discriminate between their own correct and incorrect decisions (a type II task) then the signal discriminations are subliminal. However, the mathematics underlying type II decisions reveals that type II performance can be worse than type I performance even when the task is not subliminal. I have proposed that only type II performance falling below the type II performance predicted from the observed type I performance should be considered evidence of perception without awareness. We measured type I and type II performance for utrocular detection — reporting which eye has received a stimulus in stereoscopic viewing. We found that, initially, type II performance generally fell below that predicted from type I performance, and for control tasks, type II performance fell within the predicted range. However, after ridiculous amounts of practice the difference between performance in utrocular and control tasks lessened. I will discuss the nature of the type II task, and its usefulness as a measure of perception without awareness.

This page was last updated on 16 Feb 2001.

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