Attentively tracking a feature (e.g. a disc) in an ambiguous radial motion display results in the perception of a clear motion direction (either clockwise or counter-clockwise, see Verstraten et al., Vision Research 2000; vol. 40, 3651-3664). Attentive tracking has an upper temporal limit. Here we investigate whether auditory stimulation, either in or out of synchrony with the visual stimulus can affect this tracking limit.

Two circular arrays of 10 evenly spaced discs were alternated in time and space, separated by a blank ISI. This results in successive steps of 18 degrees, and 20 attentive steps to complete one full revolution. Using the keyboard observers adjusted the alternation frequency of the two circular arrays, such that they could just attentively track a single disc for at least two full revolutions. The maximum alternation frequency at which observers could track a disc was measured for 3 main conditions: attentive tracking without auditory stimulation, tracking accompanied by an in-phase auditory stimulus and, tracking with asynchronous auditory beeps. The beeps were presented through headphones and contained no spatial information. Given the higher temporal resolution of the auditory system and assuming an auditory-visual interaction (e.g. Shams et al., Nature 2000; vol. 408, 788) we expected in-phase beeps to facilitate attentive tracking.

The results showed that in-phase auditory stimulation increased the upper temporal limit of attentive tracking. Moreover, out of phase beeps did not impair tracking performance. These results make it tempting to suggest that the mechanism responsible for the temporal resolution of visual attention receives facilitatory input from the auditory system.