Reinforcer specificity in the enhancement of conditioning by posttrial surprise

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Two experiments using male hooded rats studied the extent to which unpredicted changes in posttrial events after reinforced compound conditioning trials affected conditioning to one of the elements when the other had been previously paired with the reinforcer. In Exp I (n = 64), employing conditioned suppression of leverpressing with shock as the reinforcer, both the addition of an unexpected shock 8 sec after each compound trial and the omission of an expected posttrial shock enhanced conditioning to the nonpretrained element. By contrast, the addition and omission of posttrial free food had no effect on such conditioning. In Exp II (n = 64), employing a discriminated leverpress task with food as the reinforcer, the unexpected addition and omission of free food after each compound trial enhanced conditioning, whereas the equivalent manipulations of posttrial shock had no effect. In order for surprising posttrial events to enhance conditioning by a predicted reinforcer, they may need to be generated by changes in stimuli that are the same as or at least similar to the reinforcer. (25 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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