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Laurent Madelain; Saccadic reaction time distributions follow the matching law in a concurrent variable interval reinforcement schedule. Journal of Vision 2014;14(10):745. doi: 10.1167/14.10.745.
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Studies of decision-making process revealed that animals are sensitive to the sources and timing of rewards and use these variables to choose among alternatives. In particular experiments on foraging behavior indicate that the distribution of time among foraging sites is proportional to their relative value. These relations were expanded to a general principle of choice termed the matching law (Herrnstein, 1961) which states that the fraction of choices made to an option will match the fraction of total income earned from that option. Because saccadic reaction time distributions are known to be strongly affected by reinforcement schedules (Madelain et al, 2007) we now ask whether saccade latencies as well could match reinforcement proportions in concurrent schedule. Our procedure was similar to the one used by Sugrue et al (2004) except that reinforcement depended on saccade latencies rather than on target choice. We had one subject (the author) make saccades to a visual target stepping horizontally by 10 deg at a 0.6Hz rate. Fast and slow latencies (defined with respect to the first and last quartile of baseline RT distribution, [100-160]ms and [217-320]ms respectively) were reinforced in a concurrent Variable Interval schedule with unsignaled changes of reinforcement ratios (9/1, 1/1 or 1/9) during extensive training. Using the generalized matching equation we found that saccade latencies were well controlled by the current schedule (sensitivity=0.704, bias=-0.004). A moving 30-trials temporal window revealed that local distributions of latencies were correlated with the local ratios of obtained reward (R2=0.79, P<0.05). Interestingly, saccade peak velocities were significantly higher in the "fast" than in the "slow" latencies. These data indicate that saccade latency distributions follow the rules of other choice behavior and may depend on past behavior more than previously thought.
Meeting abstract presented at VSS 2014
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