Representational blending in human conditional learning: Implications for associative theory.

In two experiments, participants were presented with pictures of different foods (A, B, C, D, X,) and learned which combinations resulted in an allergic reaction in a fictitious patient, Mr X. In Problem 1, when A or B (but not C or D) was combined with food X an allergic reaction occurred, and when C or D (but not A or B) was combined with Y an allergic reaction occurred. In Experiment 1, participants also received Problem 2 in which A, B, C, and D interacted with foods V and W either in the same way as X and Y, respectively, or in a different way. Participants performed more proficiently in the former than in the latter condition. In Experiment 2, after training on Problem 1, participants judged whether or not novel combinations of foods (e.g., AB, CD, AD, CB) would cause an allergic reaction in Mr X. They were no more likely to indicate that AB or CD would cause an allergic reaction than AD or CB, but made their judgements more rapidly and with greater confidence on AB and CD trials than on AD and CB trials. These results (1) indicate that shared representations come to be addressed by the components of similar compounds (e.g., AX and BX) that have predicted the same outcome (an allergic reaction), and (2) are inconsistent with standard, associative theories of learning, but (3) are consistent with findings from nonhuman animals and with a connectionist interpretation of these findings.     

Recognition Memory in Pigeons for Stimuli Presented Repeatedly: Perceptual Learning or Reduced Associative Interference?

Todd and Mackintosh (1990) found that recognition memory of pigeons for pictures was better when the same pictures were used each session (a recency task) than when different slides were used (a novelty task); they attributed the superior performance on the recency task to perceptual learning. Three experiments explored two alternative accounts. One was that their use of a within-subject design could have allowed the strategy adopted in the recency task to influence adversely the strategy used in the novelty task. This possibility was ruled out by Experiment 1, which showed superior performance in the recency task when a between-subject design was used. A second account proposes that slide-reward associations formed (in both tasks) during first presentations of slides interfere with appropriate performance during second presentations (associative interference); in the recency task, however, the high long-term associative strength of the slides restricts the consequence of a single slide-reward pairing to a short-term effect, and associative interference occurs at short retention intervals only. This account was explored in Experiment 2, which found no evidence that increases in retention interval resulted in reduction of associative interference in the recency task, and in Experiment 3, where associative interference was shown to occur but was of comparable magnitude in the recency and novelty tasks. By elimination, the results support a perceptual learning interpretation.