A STEP-FUNCTION IN PIGEONS TEMPORAL GENERALIZATION IN THE PEAK SHIFT TASK

Pigeons were reinforced for pecking a key following one signal duratio n (S+) but not following another signal duration (S-). The S+ and S- w ere 2.52 and 5.67 sec, respectively, counterbalanced across birds. Sub sequent generalization tests with a range of signal durations revealed a step function, with high response rates for all durations on the S side of the distribution, low response rates for all durations on the S- side, and an intermediate rate for the intermediate duration. A co mparison group of pigeons trained with only the S+ duration showed a f lat generalization function. For the discrimination-trained birds, the delay between signal termination and opportunity to respond was subse quently varied during generalization testing. A step function again ap peared, and no evidence of subjective shortening over the delay was fo und. The overall pattern of results suggests that the birds categorize d the temporal signal into two classes and retained a categorical code over the delay.