Multisensory processing of redundant information in go/no-go and choice responses

In multisensory research, faster responses are commonly observed when multimodal stimuli are presented, as compared to unimodal target presentations. This so-called redundant-signals effect can be explained by several frameworks, including separate-activation and coactivation models. The redundant-signals effect has been investigated in a large number of studies; however, most of those studies have been limited to the rejection of separate-activation models. Coactivation models have been analyzed in only a few studies, primarily using simple response tasks. Here, we investigated the mechanism of multisensory integration underlying go/no-go and choice responses to redundant auditory-visual stimuli. In the present study, the mean and variance of response times, as well as the accuracy rates of go/no-go and choice responses, were used to test a coactivation model based on the linear superposition of diffusion processes (Schwarz, 1994) within two absorbing barriers. The diffusion superposition model accurately describes the means and variances of response times as well as the proportions of correct responses observed in the two tasks. Linear superposition thus seems to be a general principle in the integration of redundant information provided by different sensory channels, and is not restricted to simple responses. The results connect existing theories of multisensory integration with theories on choice behavior.