Choice between stimuli previously presented separately

Abstract

Three experiments examined the choice behavior of pigeons in a chamber with two adjacent keys that could each be lit with either a red or a green dot. In each experiment subjects first received several sessions of separate-stimulus training with only one color present on each trial, then a choice test with both colors present on each trial. Trials lasted a fixed period of time regardless of the number of pecks that occurred, with earned reinforcements presented at the end of the trial; no reinforcement was available during choice tests. When separate-stimulus training was arranged so that more reinforcements occurred per unit time with S 1 present than with S 2 present, either because responding was reinforced on a higher proportion of S 1 trials or because S 1 trials were shorter, S 1 was pecked more often on the subsequent choice test. When reinforcements per unit time with the stimulus present were held constant, a number of other variables had little or no effect on subsequent choice, including total number of trials presented, proportion of trials followed by reinforcement, trial length, and total number of reinforcements per session with each stimulus.