Abstract
Human perception of time is prone to errors. One remarkable example is the compression of perceived duration at the time of saccades (Morrone, Ross, & Burr, 2005) or smooth pursuit eye movements (Schütz & Morrone, 2010). We were interested whether similar misperceptions occur during other types of eye movements, which stabilize fixation. Investigating the perception of duration at the time of microsaccades might contribute to the understanding of the saccade-related compression of time, given that the neural machinery responsible for both movements is partly shared but their perceptual effects, such as visual suppression, do not necessarily overlap. To this aim, we had observers reproduce the duration of peripheral high-frequency (2.5 cyc/deg) vertically oriented Gabor patches. We chose this display as we expected it to bring about strong visual transients at the occurrence of microsaccades, which are mainly horizontally oriented and have horizontal amplitudes in the range of our stimulus wavelength. The gratings were presented for 259 to 706 ms and participants re-produced their duration with a keypress when prompted by a go-signal which appeared 700 to 1700 ms after the offset of the grating. Our observers consistently reproduced the duration as shorter when they had executed a microsaccade while the grating was present, as compared to the trials where no microsaccade was detected. This effect was evident in particular for durations above 500 ms and its magnitude, about 30 ms, was comparable to the average duration of microsaccades. Overall, our data indicate that the duration of visual events at the time of microsaccades is compressed, despite the fact that microsaccades are involuntary and are not associated with a suppression of visual signals. This finding parallels the results of experiments on saccades and smooth pursuit eye movements and questions the hypothesis that saccade-related time compression is due to reduced stimulus visibility.
LOEWE programme of the State of Hesse.