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Abigail RI Lee, Justin M Ales, Julie M Harris; Exploring how distance and duration information contributes to speed change discrimination. Journal of Vision 2019;19(10):168a. doi: 10.1167/19.10.168a.
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© ARVO (1962-2015); The Authors (2016-present)
Visual speed discrimination has been well studied. However, due to the relationship between speed, distance and time, it is difficult to determine which of these three cues is used for speed discrimination tasks. This problem can be avoided by using a speed change discrimination task, where participants discriminate a stimulus containing a step change in speed from one moving at a constant speed. Speed change discrimination tasks do not contain distance or duration cues, but these tasks are much more difficult than speed discrimination tasks (Lee, Ales & Harris, J Vis., 17(10):416, 2017; Monen & Brenner, Perception, 23(6):681–690, 1994; Snowden & Braddick, Vision Res., 31(5):907–914, 1992). One theory is that speed judgements actually involve the use distance and duration cues present, and this results in improved speed discrimination performance. Here we designed experiments that tease apart distance and duration from speed by carefully manipulating all three cues. The first experiment determined if participants’ (n=9) performance in a speed discrimination task was influenced by duration or distance by using stimuli with identical ranges of speeds, but variable duration and distance cues. We found participants’ speed discrimination performance depended only on stimulus speed, indicating participants discounted duration and distance and relied purely on speed information. In the second experiment (n=7), we tested whether adding distance or duration information improved speed change discrimination performance. We compared performance in conditions that only contained speed information with performance for stimuli that had additional distance or duration cues. We found no difference in performance between conditions. Our results suggest that speed is the cue used for speed discrimination, and the absence of distance and duration information is not what makes speed change discrimination difficult.
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