DOES A FEATURE-POSITIVE EFFECT OCCUR DURI NG CLASSICAL-CONDITIONING IN HUMANS

Jenkins and Sainsbury (1969, 1979) first described an asymmetry in pig eon's operant discrimination learning which they called a feature-posi tive effect. Subsequent studies demonstrated that other animals as wel l as humans also show a similar asymmetry. The effect is often explain ed as being caused by a bias in information processing which results f rom the neglect of negative information as a discriminative cue. The e ffect has also been observed in classical conditioning experiments, bu t not yet with human subjects. Sometimes, however, a reversal of the a symmetry, i.e., a feature-negative effect, has been observed. The expe riment reported here primarily intended to demonstrate a feature-posit ive effect in a classical conditioning procedure with human subjects. Secondly, we also wanted to test an alternative explanation of the fea ture-positive effect. We found that a substantial feature-positive eff ect does indeed occur during classical conditioning in human subjects. Our results, however, did not fully support the alternative explanati on based on rule learning.