Figure 3.

Example of choice behaviors. Vertical bars in the upper portions of the inset indicate the left (L) and right (R) choice in each trial. Tall and short bars show rewarded and non-rewarded trials, respectively. Dark blue and pink bars indicate trials with variable- and fixed-reward conditions and lines in the center indicate the left-choice frequency of a given rat in the last 20 trials. The reward probability of the fixed-reward condition was 50–90% for the left-right choice. The reward-probability setting of variable-reward-condition block is shown at the top. In blocks with a light-blue color, more-rewarding choices of variable- and fixed-reward conditions were identical. Rats succeeded in distinguishing the variable- and fixed-reward conditions for action learning.