Biological significance attenuates overshadowing, relative validity, and degraded contingency effects

Miller and Matute (1996) showed that blocking is attenuated when the blocke d conditioned stimulus (CS) is "biologically significant" (i.e., when the C S has the potential to elicit vigorous responding of ang kind). To the exte nt that blocking is representative of cue competition, this finding suggest s that biological significance protects CSs against cue competition effects in general. In the present experiments we tested this possibility by exami ning the influence of biological significance of CSs on other examples of c ue competition, namely, overshadowing, the relative stimulus validity effec t, and the de graded contingency effect in rats. In Experiment 1, we found that intense auditory stimuli induced transient unconditioned lick suppress ion, thereby indicating that intense sounds were of high inherent biologica l significance. In Experiment 2A, we found that cues with high inherent bio logical significance were protected from overshadowing. In Experiment 2B, t his finding was extended to cues with high acquired biological significance , which was obtained through prior pairings with a reinforcer of the valenc e opposite to that used in the overshadowing treatment. In Experiments 3 an d 4, we found that cues with high inherent biological significance attenuat ed the relative validity effect and the degraded contingency effect, respec tively. These results lend support to the view that biological significance (inherent and acquired) protects stimuli from cue competition effects, a f inding that is problematic for many contemporary theories of learning.