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Celine Paeye, Laurent Madelain; Finding the target as a reinforcer of saccadic amplitude variability in a visual search task.. Journal of Vision 2012;12(9):1236. doi: 10.1167/12.9.1236.
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We recently showed that part of saccadic amplitude variability may be controlled by operant learning (Paeye & Madelain, 2011). Saccadic amplitude distributions were reinforced with a tone depending on amplitude variability criteria.
In the present study we designed a new paradigm involving a visual search task to test whether finding a target among distractors could also be effective to reinforce various saccadic amplitude variability levels: the target was visible only if the saccadic amplitude variability reached a specific criterion.
Subjects were instructed to perform a visual search task. At the beginning of each trial 24 distractors (0.3 deg circles with a dash tilted to the left) were displayed. We used a gaze-contingent criterion to display the target (a 0.3 deg circle with a dash tilted to the right) at the item location that was looked at.
In a first experimental condition the target appeared when the current saccadic amplitude was rare (to increase amplitude variability). In a second experimental condition the target was displayed when the current saccadic amplitude was frequent (to decrease amplitude variability). In a control group target appearance was independent of saccadic amplitudes.
U-value (measuring distribution uncertainty) increased from a baseline of 0.57 on average to 0.86 at the end of the first experimental condition and then returned to 0.51 after changing the reinforcement criteria. In the control group averaged U-value first decreased (from 0.56 to 0.49) and then remained at a low level (0.52).
These results were confirmed in a second experiment. Furthermore we found that learning transferred to regular visual search trials (in which the target was displayed independently of subjects behavior).
Seeing the target is a consequence controlling saccadic properties. Moreover these results confirm that an operant learning process can guide saccadic amplitude variability.
Meeting abstract presented at VSS 2012
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