Reinforced stimulus preexposure effects as a function of US intensity: Implications for understanding the Hall–Pearce effect

Three conditioned suppression experiments examined the Hall–Pearce (1979) negative transfer effect in rats. Experiment 1 replicated the effect: CS-USweak pairings retarded subsequent fear conditioning to the CS as a result of CS-USstrong pairings. The size of this retardation was less than that produced by non-reinforced CS presentations (latent inhibition). When the magnitude of the USweak was reduced in Experiment 2, the Hall–Pearce effect was greater than latent inhibition. Experiment 3 confirmed the findings of the two previous experiments, and demonstrated that magnitude of the Hall–Pearce negative transfer effect is inversely related to the magnitude of the USweak. From these findings it is suggested that the Hall–Pearce effect consists of a balance between a positive transfer of associative strength, and negative transfer based on CS- and US-preexposure effects.