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The aim of this study was to delineate the minimal conditions for extinction of Pavlovian modulation in humans. Previous experiments at our lab showed that, after X ? A+/A� acquisition training, X� trials did not extinguish differential X ? A+/A� responding, while X ? A� trials did. Additionally, X ? A� extinction training seemed only to extinguish differential X ? A+/A� responding, while leaving differential responding on a concurrently trained Y ? B+/B� discrimination intact. It thus seemed that the X ? A+/A� discrimination can only be extinguished by X ? A� extinction trials. (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16�24, 1986), on the other hand, found that the minimal conditions for extinction were broader in pigeons: Namely, he found that an acquired X ? A+/A� discrimination could be extinguished by presenting the original feature X in combination with a different target (B) that was minimally trained as an exciter. We thus wanted to examine whether this was also the case in humans. We found that nonreinforced X ? B� presentations did not abolish discriminative X ? A/A responding when target B was a nonreinforced stimulus. Nonreinforced X ? B� trials did extinguish the X ? A+/A� discrimination when target B had previously been trained as a target for modulation (X ? B+/B� or Y ? B+/B� training) or as a reinforced exciter (B+). Our results thusf parallel and extend those in nonhuman animals (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16�24, 1986).
