BIOLOGICAL SIGNIFICANCE AS A DETERMINANT OF CUE COMPETITION

Many researchers have noted the similarities between causal judgment i n humans and Pavlovian conditioning in animals. One recently noted dis crepancy between these two forms of learning is the absence of backwar d blocking in animals, in contrast with its occurrence in human causal ity judgment. Here we report two experiments that investigated the rol e of biological significance in backward blocking as a potential expla nation of this discrepancy. With rats as subjects, we used sensory pre conditioning and second-order conditioning procedures, which allowed t he to-be-blocked cue to retain low biological significance during trai ning for some animals, but not for others. Backward blocking was obser ved only when the tar get cue was of low biological significance durin g training. These results suggest that the apparent discrepancy betwee n human causal judgment and animal Pavlovian conditioning arises not b ecause of a species difference, but because human causality studies or dinarily use stimuli of low biological significance, whereas animal Pa vlovian studies ordinarily use stimuli of high biological significance , which are apparently protected against cue competition.