Shin'ya Nishida1, Alan Johnston. 1. Human and Information Science Laboratory, NTT Communication Science Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi-shi, 243-0198, Kanagawa, Japan.
Abstract
BACKGROUND: When simultaneous visual events appear to occur at different times, the discrepancy has generally been ascribed to time differences in neural transmission or cortical processing that lead to asynchronous awareness of the events. RESULTS: We found, however, that an apparent delay of changes in motion direction relative to synchronous color changes occurs only for rapid alternations, and this delay is not accompanied by a difference in reaction time. We also found that perceptual asynchrony depends on the temporal structure of the stimuli (transitions [first-order temporal change] versus turning points [second-order temporal change]) rather than the attribute type (color versus motion). CONCLUSIONS: We propose that the perception of the relative time of events is based on the relationship of representations of temporal pattern that we term time markers. We conclude that the perceptual asynchrony effects studied here do not reflect differential neural delays for different attributes; rather, they arise from a faulty correspondence match between color transitions and position transitions (motion), which in turn results from a difficulty in detecting turning points (direction reversals) and a preference for matching markers of the same type.
BACKGROUND: When simultaneous visual events appear to occur at different times, the discrepancy has generally been ascribed to time differences in neural transmission or cortical processing that lead to asynchronous awareness of the events. RESULTS: We found, however, that an apparent delay of changes in motion direction relative to synchronous color changes occurs only for rapid alternations, and this delay is not accompanied by a difference in reaction time. We also found that perceptual asynchrony depends on the temporal structure of the stimuli (transitions [first-order temporal change] versus turning points [second-order temporal change]) rather than the attribute type (color versus motion). CONCLUSIONS: We propose that the perception of the relative time of events is based on the relationship of representations of temporal pattern that we term time markers. We conclude that the perceptual asynchrony effects studied here do not reflect differential neural delays for different attributes; rather, they arise from a faulty correspondence match between color transitions and position transitions (motion), which in turn results from a difficulty in detecting turning points (direction reversals) and a preference for matching markers of the same type.