Figure 2.

Choice behavior governed by reward size. (A) Mean ± SEM frequency of switching choice from one target to the other, as a function of the size of the reward obtained on the previous trial. For display purposes, the reward magnitudes were binned into bins of small (valve opening durations <80 ms), medium (valve opening durations ≥80 ms and <160 ms) and large rewards (valve opening durations ≥160 ms). The SEMs are smaller than the data point markers in this figure. (B) The histogram of the number of consecutive choices of the same target. The dashed line represents an exponential fit. (C) Mean ± SEM reaction time as a function of the magnitude of the reward size obtained on the previous trial. (D) Histograms of actual reward values (valve opening times) obtained by the monkeys for choosing an option from a distribution characterized by a particular mean value.