The role of temporal integration in auditory stream segregation

Grouping distinct, temporally separated sounds is assumed to follow Gestalt principles, such as similarity or proximity. In the auditory streaming paradigm, the probability of perceiving all sounds as part of the same repeating pattern (the integrated percept) increases when the inter-stimulus interval (ISI) is increased from medium to long intervals. However, ISIs shorter than 50 ms have not been systematically explored. Here we show that below ca. 60 ms intervals the direction of the effect of ISI on perception is reversed compared to longer ISIs: decreasing the ISI increases the probability of the integrated percept. This suggests that temporal proximity plays a different role in auditory stream segregation at very short than at longer ISIs. As the effect of temporal proximity may vary among individuals, we tested whether the proportion of the integrated reports with short ISIs could be associated with individual differences in the temporal resolution of the central auditory system. We found that individual differences in the temporal integration threshold (as measured by a Temporal Order Judgment task) correlated with the percentage of integrated percept reports in some of the short-ISI regions. Although this result cannot be regarded as strong evidence, it is compatible with the notion that temporal integration plays a role in auditory stream segregation at short ISIs