Content area
Full text
The differential outcomes effect refers to the increase in accuracy obtained in discrimination tasks when rewards provided for correct responses vary according to the stimulus presented. The present research examined this effect in a sample of university students discriminating multiple stimuli. A computer task was used to teach the meanings of 15 Japanese kanji characters, with both immediate (photos) and backup (lottery prizes) rewards following correct responses. Students were randomly allocated to one of three conditions: a differential condition (photos and prizes were uniquely associated with specific kanji), a partial differential condition (photos but not prizes were uniquely associated with specific kanji), and a nondifferential condition (photos and prizes were randomly associated with specific kanji). Participants in the differential condition learned the kanji meanings more quickly than those in the nondifferential condition. Accuracy in the partial differential condition was intermediate to, and not significantly different from, the other two conditions. These results extend the generality of the differential outcomes effect and have important practical implications.
In a standard discrimination procedure, common rewards are provided for correct responses to different stimuli. In a differential outcomes procedure, the rewards provided for correct responses vary according to the stimulus presented. The improvement in accuracy obtained with the latter procedure, compared to that obtained with common or random rewards, is known as the differential outcomes effect (DOE).
Trapold (1970) was the first to demonstrate a DOE. His experiment was designed to assess a two-process theory of learning. He suggested that an association is formed not only between the stimulus (S) and response (R), but also between the stimulus and the reinforcer (SR). The predicted S-SR association meant that the stimulus would come to elicit a learned representation/expectation of the reinforcer that consistently followed it. If this were the case, one would expect higher accuracy when differential outcomes are used, as additional discriminable information is available at the time of responding. Trapold tested this reasoning by teaching rats to discriminate between a clicker and a tone. Responses to the left bar were reinforced after presentation of the clicker. Responses to the right bar were reinforced after presentation of the tone. Rats who experienced differential outcomes received food for one type of correct response and sucrose solution for the other....