Signal intensity, task context, and auditory-visual interactions.

A study is reported of the effect of signal intensity on immediate cross-modal bias between vision and audition. Each signal was presented at high or low intensity, giving rise to four conditions. The study also dealt with the effectiveness of instructions and task context in directing attention. Two kinds of task (pointing) contexts were compared: a constant or unimodal context in which the modality of the target signal was the same throughout a session, and a bimodal one in which it changed from trial to trial. In both conditions subjects were instructed that the signals might come from the same or from different positions, depending on the trial. For visual bias of audition the results show that a signal with high intensity was more biasing and less biased than one with low intensity. Auditory bias of vision did not reach significance in any of the four intensity conditions. Type of task context had no effect on the extent of bias, suggesting that a constant-task (unimodal) context was no more effective in directing attention than instructions alone.