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Abigail Lee, Justin Ales, Julie Harris; Temporal integration of speed change in motion perception. Journal of Vision 2018;18(10):293. doi: 10.1167/18.10.293.
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Speed change discrimination, where a stimulus containing a step change in speed is discriminated from a constant speed stimulus, is more difficult than discriminating between two separate stimuli with different constant speeds (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). Here, we explore one possible explanation for this: if there is no temporal separation between two presented speeds, there could be temporal integration of motion signals, making it harder to discriminate between the speeds. 8 naïve observers completed a speed change discrimination task in which a moving line either had a step increase or decrease in speed. The task was to indicate whether the stimulus speed increased or decreased. Three different temporal separation conditions were used. In the first, the moving line instantaneously changed speed at some point during its motion (0s temporal separation condition). In the other conditions, the line disappeared for either 0.5s or 1s, then reappeared in the same location and continued along its trajectory at the new speed (0.5s temporal separation and 1s temporal separation conditions). We explored two ranges of speeds, with initial speeds of either 2deg/s ('slow') or 20deg/s ('fast'). Thresholds, as measured by Weber fractions, were not significantly different across temporal separation conditions using fast speeds (thresholds ± SEM, 0s: 0.138 ± 0.012; 0.5s: 0.144 ± 0.008; 1s: 0.136 ± 0.008). This was also found for conditions using slow speeds (thresholds ± SEM, 0s: 0.196 ± 0.038; 0.5s: 0.183 ± 0.027; 1s: 0.165 ± 0.018). Adding temporal separation therefore does not decrease the difficulty of the speed change discrimination task. These results suggest that temporal integration of speeds alone is not responsible for making speed change discrimination a difficult task.
Meeting abstract presented at VSS 2018
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