Cross-modal enhancement of perceived brightness: sensory interaction versus response bias.

Stein, London, Wilkinson, and Price (1996) reported the presence of cross-modal enhancement of perceived visual intensity: Participants tended to rate weak lights as brighter when accompanied by a concurrent pulse of white noise than when presented alone. In the present study, two methods were used to determine whether the enhancement reflects an early-stage sensory process or a later-stage decisional process, such as a response bias. First, enhancement was eliminated when the noise accompanied the light on only 25% versus 50% of the trials. Second, enhancement was absent when tested with a paired-comparison method. These findings are consistent with the hypothesis that the sound-induced enhancement in judgments of brightness reflects a response bias, rather than an early sensory process--that is, enhancement is the result of a relatively late decisional process.