Stimulus exposure effects in human associative learning

Learning that one cue (CS) predicts a second, salient cue (US) can often be slowed by prior exposure to one or both stimuli. In animals, CS±US learning is more strongly retarded following uncorrelated exposure to both CS and US than following exposure to the US alone. In this paper we present several studies showing a similar effect in humans, using a computer-based task. Experiments 1 and2useda between-groupsdesign anddemonstrateda strongCS/US exposure effect, whether or not theUSwas signalled by a neutral cue during exposure. Experiment 3 demonstratedsimilar effects using awithin-subjects design. Overall, these results are consistent with several theoretical interpretations and suggest that uncorre-lated CS/US exposure leads to a robust retardation of subsequent CS±US learning in humans. Some of the most interesting recent paradigms for exploring learning have exploited the fact that prior exposure to stimuli can affect the rate at which associations between those stimuli are subsequently learned. For example, learning that a previously neutral cue (the conditioned stimulus or CS) predicts a salient outcome (the unconditioned stimulus or US) is retarded by prior exposure to the CS alone; this effect has been termed ` l̀aten