Sensory interaction: vision is modulated by hearing.

An irrelevant noise was turned on at various points during a visual reaction-time task. Latencies were reliably smaller than on quiet trials, provided the noise was turned on when a subject was looking at a relevant visual stimulus. This effect occurred regardless of whether the distribution of interstimulus intervals was constant or varied during a session, as well as independently of a subject's base rate of response and level of practice in the task. But it disappeared if reaction times in completely noisy sessions were compared to performances in quiet stimulated by a test form, but not with the particular ear stimulated by a noise. A model is suggested for these and related results in which the arousal elicited by a loud sound in the central nervous system either activates associative memories of form, inhibits early components of striate cortical unit response to the intensive properties of a visual stimulus, or both.