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Geoffrey Harrison, Chelsia Lau, Jason Rajsic, Daryl Wilson; Effect of object substitution masking on the perceived duration of supra-threshold object representations. Journal of Vision 2015;15(12):1231. doi: 10.1167/15.12.1231.
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© 2017 Association for Research in Vision and Ophthalmology.
Object substitution masking (OSM) describes a decrease in the ability to accurately report the identity of an object (the target) when a surrounding four-dot mask (4DM) remains on the screen after the offset of the target. Current theories propose that OSM results from the visual system updating the initial target plus mask representation in favor of the later mask only representation. Notably, object updating theories of OSM are underspecified with regard to the temporal dynamics of the updating process. To examine the possibility that OSM results in the reduction of a target’s perceived duration, two experiments combined a temporal order judgement task with an OSM paradigm. In Experiment 1, eight objects (two targets and six distractors) were presented along with two 4DMs which either overlapped the two targets or two distractors. On every trial, the presentation duration of the distractors and one of the targets were equivalent (100 ms) whereas the other target’s duration was varied (25, 50, 75, 100, 125, 150 or 175 ms). Participants made a forced choice judgement of the relative duration of the two targets. Accuracy was used to generate psychometric curves representing perceived durations of targets. Critically, the offset of one of the masks was always simultaneous with its associated object, whereas the offset of the other mask was delayed by 300 ms. When masks overlapped the targets, there was a shift in the psychometric curve indicating that the delayed mask reduced the perceived duration of its associated target. Experiment 2 extended the standard presentation duration of all the objects to 500 ms and used a blocked design in which the masks either overlapped the targets, or were radially displaced from them. Both experiments provide novel evidence that OSM can reduce the perceived duration of supra-threshold objects without affecting detection accuracy.
Meeting abstract presented at VSS 2015
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