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Srimant Tripathy, Haluk Ogmen, Jerome Gabarretta, Mark Baresh; MEMORY FOR DIRECTIONS OF MOTION OF MULTIPLE OBJECTS UNDERGOING BILINEAR MOTION. Journal of Vision 2012;12(9):719. doi: 10.1167/12.9.719.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: When several objects move along linear trajectories, information regarding their direction-of-motion is stored into high-capacity transient ("sensory") and low-capacity sustained (Visual Short-Term Memory, VSTM) memory systems by use of graded resources (Shooner et al., JOV, 2010). We now extend our earlier study to objects moving along bilinear trajectories, i.e. trajectories with a large deviation halfway through the trial. This task involves monitoring current as well as previous states of the objects. Methods: Observers attentively tracked multiple objects (n = 1 to 4) with bilinear motion trajectories and were cued to report one (Partial-Report, PR) or all (Full-Report, FR) directions of motion, either before deviation or after deviation. Experimental conditions (PR_before-deviation, PR_after-deviation, FR_before-deviation, FR_after-deviation) were randomly interleaved in each block. We measured precision as a function of stimulus duration (Exp1; t = 200-1200ms, n=3), set-size (Exp2; t = 800ms, n = 1 to 4) and the cue-delay (Exp3; t = 800ms, n = 3, delay = 0-1200ms; the delay was applied to after-deviation trials only). Results: Precision was greater for after-deviation conditions than for before-deviation conditions, consistent with the longer duration of decay of sensory memory for the latter. In Exp1, precision improved with duration and saturated around 800ms in all four conditions. Exp2 showed steeper loss of precision for FR compared to PR and for before-deviation compared to after-deviation. In Exp3, the precision in the after-deviation condition did not decay to the precision in the before-deviation condition, even when the cue in the after-deviation condition was delayed by 1200ms. Conclusions: Our results suggest that decay of sensory memory partially accounts for the loss of precision during tracking deviations in trajectories (Tripathy & Barrett, JOV, 2004). In addition, the performance in the before-deviation conditions cannot be explained by any model of tracking that only monitors the current state of tracked objects.
Meeting abstract presented at VSS 2012
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