Effect of stimulus intensity on response time distribution in multisensory integration

To increase the efficiency of multimodal user interfaces, one has to design them according to how multimodal features appear in the real world. Although spatial coincidence and matching intensity levels are important for perception, these factors received little attention in human-computer interaction studies. In our present study we aimed to map how spatial coincidence and different intensity levels influence response times. Sixteen participants performed a simple auditory localization task, where sounds were presented either alone or together with visual non-targets. We found that medium intensity visual stimuli facilitated responses to low intensity sounds. Analyses of response time distributions showed that intensity of target and non-target stimuli affected different parameters of the ex-Gaussian distribution. Our results suggest that multisensory integration and response facilitation may occur even if the non-target has low predictive power to the location of the target. Furthermore, we show that the parameters of the ex-Gaussian distribution can be related to distinct cognitive processes. The current results are potentially applicable in the design of an intelligent warning system that employs the user's reaction time to adapt the warning signal for optimal results.