In two experiments hungry rats received extensive training to lever press for food outcomes before one outcome was devalued by aversion conditioning and responding tested in extinction. If the rats were trained on a concurrent schedule in which two responses yielded different outcomes, performance during the extinction test was reduced by devaluation of the associated outcome. By contrast, if a single response was trained concurrently with the noncontingent presentations of the other outcome, test performance was insensitive to devaluation of the contingent outcome. This finding demonstrates that training on a schedule that offers a choice between responses that yield different outcomes prevents the onset of behavioral autonomy.

The capacity for goal-directed behavior requires not only the encoding of the response-outcome relationship but also the ability to resolve conflict induced by competing responses. Recent neuroimaging studies have identified the prefrontal cortex as critical for resolving conflict between competing responses. At present, however, much of this evidence is indirect, and the necessity of dorsomedial prefrontal cortex (dmPFC) function for the resolution of conflict in goal-directed behavior has not been assessed. Here, we develop a rodent paradigm to investigate response conflict caused by the concurrent activation of a correct and incorrect response. In this paradigm, the outcome of one response also acts as a discriminative stimulus signaling that the other response is correct. Whereas rats with a functional dmPFC are able to resolve this conflict, inactivation of dmPFC using an infusion of muscimol produced a deficit by selectively interfering with their ability to inhibit the incorrect, competing response.

The ability of rats to solve a discrimination between two objects that differ in length was investigated in five experiments. Using a rectangular swimming pool, Experiment 1 revealed it is easier to locate a submerged platform when it is near the center of a long rather than a short wall. For Experiments 2–4, the objects were black or white panels pasted onto the gray walls of a square pool, with two long panels pasted to two opposing walls and two short panels pasted to the remaining walls. The platform was easier to locate when it was placed near the middle of a long rather than a short panel. This effect was found when the long panels were twice (Experiments 2–4) or four times the length of the short panels (Experiment 4). Experiment 5 demonstrated that rats can solve a discrimination between panels of length 15 and 45 cm more readily than when they are 70 and 100 cm. The results are consistent with the claim that generalization gradients based on stimulus magnitude are steeper for stimuli that are weaker rather than stronger than the stimulus used for the original training.

. (2013) 'Overshadowing of geometry learning by discrete landmarks in the water maze : e ects of relative salience and relative validity of competing cues.', Journal of experimental psychology : animal behaviour processes., 39 (2). pp. 126-139.Further information on publisher's website:Publisher's copyright statement:c 2013 APA, all rights reserved. This article may not exactly replicate the nal version published in the APA journal. It is not the copy of record.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

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