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Sabine Born; Repetitive visual pattern masking enlarges the perceived distance between stimuli (but does not diminish crowding). Journal of Vision 2018;18(10):857. doi: 10.1167/18.10.857.
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© ARVO (1962-2015); The Authors (2016-present)
Many visual phenomena attest how masks reduce the visibility of a stimulus. But can masking also affect an object's spatial representation? In the current study, I explored effects of pattern masks on the perceived spacing between two clearly visible objects. On each trial, two pairs of bars were presented for a total duration of two seconds, one pair to the left, and one to the right of central fixation. Participants were asked to judge in which pair the two bars were further apart. The bars of a pair were either presented continuously, or they were flickering on and off in synchrony (at a frequency of 5 Hz), or they were presented alternating, giving the impression of one single object moving back and forth (apparent motion). With flickering or alternating bars, a pattern mask consisting of small grey squares of random luminance could be presented during the off-phases of the stimuli (50 ms). Although these masks may impoverish the representation of the bars, they remained perfectly detectable due to their long and repetitive presentation. Surprisingly, with masking, the distance between the two bars was overestimated when compared to an equivalent pair presented without mask on the other side. But also when pitted against a continuously presented pair of bars, a strong and robust bias emerged to report the distance between the masked bars as larger. Following up on this effect, I reckoned that if pattern masking enlarges the perceived spacing between objects, it may also diminish crowding. In a first pilot experiment, this was not the case. Quite to the contrary, a similar repetitive masking procedure led to poorer performance in a crowding setup. The stimuli in the masked and unmasked conditions were not equated for visibility, though, which may explain the disruptive effect of the masks on identification accuracy.
Meeting abstract presented at VSS 2018
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