Ss of the experimental group responded to a weak tone accompanied by a small increase in the general illumination of the room. S's of the control group were given the same tone without the light. Both groups were instructed to signal E that the tone was heard by pressing a telegraph key. The Ss were then given 30 trials of the tone and then 10 trials of the light and 10 trials of the tone in random order. Finally, one auditory threshold was obtained when the light was present with the tones, and another threshold was obtained without the light. S's of the experimental group showed a significant increase in auditory acuity when the light was present over their auditory acuity without the light. The control group showed no difference in auditory acuity. (PsycINFO Database Record (c) 2006 APA, all rights reserved)