Extinction of stimulus elements decreases the rate of conditional discrimination learning

Pigeons were trained on a successive discrete-trial conditional discrimination, in which either of two colors appeared on the center key and either of two forms appeared on the two side keys. Some combinations of color and form (S+ trials) were followed by food; other combinations (S-trials) were followed by no food. The colors on the center key appeared throughout the intertrial interval (ITI) preceding the trial period in which both the color and the form compound were presented or the color appeared only during the trial period in compound with the forms. Presentation of the colors during the ITI substantially degraded acquisition of two separate types of conditional discrimination. The results show that the temporal correlation of the eolors-with food, independent of their association with the form cues, played a substantial role in determining their availability for acquisition of the conditional discrimination.