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Junji Watanabe, Susumu Tachi; Visual persistence of saccade-induced image smear. Journal of Vision 2005;5(8):447. doi: 10.1167/5.8.447.
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Visual persistence has been studied mainly in normal viewing, which indicates eyes are fixed. Recently, some reports have demonstrated that the result of temporal judgment tasks in perisaccadic periods have different tendencies than in normal viewing (e.g.,Yarrow et al., 2001). The reports indicate that a person's subjective sense of time, or internal clock, ticks more slowly in perisaccadic periods. Few studies, however, have investigated the mechanism of time perception around the time of a saccade. We, therefore, measured the visual persistence of a perisaccadic light stimulus, which is fundamental for studying perisaccadic time perception. Based on Di Lollo's sequential method (1977), we specifically determined the duration of a saccade-induced image smear, which is painted by a stationary light stimulus when an eye movement is performed. In our experiment, a flickering light stimulus was presented through the duration of a saccade (34 ms) in a dark environment, and a dot array (saccade-induced image smear by a flickering light stimulus) was observed due to retinal afterimages. After the presentation of the dot array, another light point was presented with one of six inter-stimulus intervals (0, 40, 80, 120, 160, 200 ms). The observers were asked to answer whether the image smear and the light point were perceived as one image or they were sequentially presented. We defined PSE of the inter-stimulus interval as the duration of saccade-induced image smear. We compared the duration for saccade-induced image smear with the duration when a physically spreading light array was observed in normal viewing. Although the results of temporal judgment tasks in previous studies indicated a slowing of the internal clock in perisaccadic periods, our results show that the duration of the saccade-induced image smear lasts as long as the duration of afterimages induced by a physically moving illuminant.
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