Impact of evoked reward expectation on ocular information during a controlled card game

The possibility of assessing reward expectations was examined using the environment of a poker game which was controlled by the experimenters. Subjects were asked to express their degree of expectation of obtaining a reward from their bets at two stages of each hand. In the results, pupils dilated according to the extent of a subject’s reward expectation. In particular, as mean pupil sizes for the 2nd round of betting increased with the subject’s expectation of a reward during the game, there were significant differences between the three grades of expectations. Also, pupil sizes correlated with the change in expectation between the two rounds of each hand. Other indices such as saccade frequency and microsaccade frequency also responded to the expectation of a reward. These results provide evidence that metrics of oculo-motors can be an index of the level of reward expectation in the environment of a controlled card game.