Abstract
A prevailing view is that audiovisual integration requires temporally coincident signals. Here we demonstrate that audiovisual temporal coincidence alone (i.e., synchrony) does not necessarily lead to audiovisual binding. In visual search experiments, subjects found a modulating visual target vastly more efficiently when it was paired with a synchronous auditory signal. By manipulating the shape of temporal modulation (sine-wave vs. square-wave vs. difference-wave; harmonic sine-wave synthesis; gradient of onset/offset ramps) we show that abrupt audiovisual events are required for this search efficiency to occur, and that sinusoidal audiovisual modulations do not support efficient search. Thus, temporal alignment will only lead to audiovisual integration if the changes in the component signals are both synchronized and transient. We propose that transient signals are necessary in synchrony-driven binding to avoid spurious integration when unrelated signals occur close together in time.