Dynamics of choice during estimation of subjective value

This study characterized preferential choice in binary trials and investigated intra-session variations in response time (RT). In Experiment 1, participants (N=77) were asked to choose the preferred of two images of body wash; all unique combinations of 19 images were presented. The results showed: (a) marked and consistent individual preferences for specific stimuli; (b) RT decreased monotonically with increasing exposure to each stimulus; (c) RT decreased exponentially as a function of relative preference ranking of the 2 images in a trial; and (d) a regression model efficiently predicted trial RT as a function of exposure and relative preference. Experiment 2 (N=112) explored the effect of amount of exposure on RT, and relative preference as a function of the type of choice task (a previously completed vs. a new choice task). The results showed that: (a) within a single choice task, amount of exposure and relative preference between the stimuli predicted the systematic changes in RT observed in Exp. 1; and (b) when the choice task changed, the effects of previous amount of exposure, and relative stimulus preference did not transfer to the new task.