Low occasion setter salience results in learning conditional stimulus partial reinforcement instead of occasion setting

In real-world settings, stimulus and outcome associations often depend on situational factors, such as Pavlovian occasion setters (OSs), which disambiguate whether a conditional stimulus (CS) will predict an outcome (unconditional stimulus; US). Whereas previous studies show that OSs are often lower in salience than CSs, no study has examined how low-salience OSs affect learning. In two conditioning experiments, we investigated this from the premise that inconsistently reinforced CSs prompt searching for additional stimuli (OSs) that indicate whether the CS will be followed by the US. Occasion setting learning was assessed using extinction rate—as partial reinforcement slows extinction relative to continuous reinforcement—and self-reported latent learning of stimuli. We hypothesized that a high-salience OS would result in faster extinction rates and occasion setting learning, whereas a low-salience OS would result in slower extinction rates and CS partial reinforcement learning. The results of Experiment 1 were mixed; there was no effect of OS salience on extinction rate, but the results for latent learning supported the hypothesis. We conducted Experiment 2 to specifically test extinction rate, and the results supported our hypothesis. The findings suggest that if a salient OS is found, occasion setting is learned; otherwise, CS partial reinforcement is learned.