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The Differential Outcome Effect with Typical Adult Humans




Schmidtke, Kelly

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A mechanism that affects nonhuman animal learning is expectation, as explored with experiments that produce the differential outcome effect (DOE). To obtain the DOE, animals are trained using a differential outcomes procedure where each correct choice response is correlated with a particular outcome. Animals trained with the differential outcomes procedure learn to "expect" a particular reinforcer, and this "expectation" helps them learn tasks faster and perform them more accurately than animals that cannot "expect" a particular reinforcer. While the DOE appears when nonhuman animals are trained using the differential outcomes procedure, it has been more elusive when typical adult humans are trained using the same procedure. Contrary to past experiments, the present experiments demonstrate that expectancies do affect typical adult human learning. Previous failures to obtain the DOE with typical adult humans result because previous experiments have employed tasks that were too simple and participants acquired the associations quickly regardless of the expectancies they could or could not form. In the present Experiment 1 participants saw a Kanji character (a Japanese word), and then 9 English words. If the participant selected the correct English word, then they saw either a correlated or uncorrelated outcome followed by a second correlated or uncorrelated outcome. If the participants choose the wrong word, then they saw either corrective or noncorrective feedback. Because Kanji are less discriminable and 15 associations were required, this task proved difficult for participants and the DOE was obtained. In Experiment 2, after a participant made an incorrect choice response they saw noncorrective feedback. Participants in Experiment 1 acquired the information faster and more completely than participants in Experiment 2 but the DOE was obtained regardless of the type of feedback given. In Experiment 3, after a participant responded correctly they saw an entry into a prize lottery and then saw a picture. Those participants who saw a correlated prize acquired the kanji’s meanings faster than those who saw an uncorrelated prize, but the picture condition had no effect. These results suggest that the temporal placement of the outcomes matter. In Experiment 4, the participants learned who painted 15 abstract paintings. The DOE was not obtained in this experiment because all participants learned the task quickly. However, an additional post test indicates that these participants also learned about proximal outcomes, suggesting that associations are learned not only between stimuli and responses but also between responses and outcomes. These experiments add to the DOE literature and comparative psychology by asserting that expectancies are a general mechanism that affects species learning.