Learning About Associations: Evidence for a Hierarchical Account of Occasion Setting

In 2 experiments rats were trained on a switching discrimination, with 4 occasion setters, A, B, C, and D and 2 target stimuli, x and y. When signaled either by A or by B, x was reinforced with food and y was not, whereas when signaled either by C or by D these reinforcement relations were reversed (i.e., A: → x+, A: y → -, B: x → +, B: y → -, C: x → -, C: y → +, D: x → -, D: y → +). In a subsequent Stage A was paired with shock, and then the degree to which food-reinforced (Experiment 1a) and nonreinforced (Experiment 1b) presentations of x and y were capable of eliciting fear was assessed. Those conditioned stimulus (CS)/unconditioned stimulus (US) relations that had been operative in the presence of the fear-eliciting occasion setter A (i.e., x → +, y → -) elicited more fear than the alternative CS/US combinations (i.e., x → -, y → +). The implications of these findings are discussed with reference to theories of occasion setting and of configural learning.