Differential reward outcome learning in adult humans.

Differential reward outcome learning provides a unique reward outcome for each condition of a conditional discrimination task, and this increases the rate at which these tasks can be learned. The present experiment aims to show that irrespective of any difference in learning rate, conditional discrimination tasks and differential reward outcome tasks are solved using different strategies. Two groups of 30 adult subjects were taught a series of conditional visual discriminations. One group received different reward outcomes for each condition, whilst the other group received the same reward outcome for each condition. Both groups learned the visual discriminations at the same rate. Subjects were then taught a new conditional cue with a subset of previously learnt discrimination problems and then required to transfer the newly learnt instruction cue to the remaining discrimination problems that had been previously learnt. Although both groups appeared to transfer the newly learnt cue at the same rate, the subjects performing the differential reward outcome task learnt to a criterion level of performance with fewer errors. The results are discussed in relation to evidence from monkeys indicating different neural mechanisms underlying the learning of both tasks.