Dynamics of time matching: Arousal makes better seem worse.

Matching of time allocation across alternatives in proportion to relative reinforcement rates is a ubiquitous finding in the animal-learning literature on choice. The dynamics of the underlying mechanism, however, remain poorly understood. A recent finding by Belke (1992) profoundly challenges scalar expectancy theory (SET; Gibbon et al., 1988) and other accounts of matching in concurrent variable interval (VI) schedules. He studied concurrent probe tests of stimuli associated with equal VIs but trained in alternative concurrent pairs. In training, one was preferred and the other not. Unreinforced probes revealed a strong preference for the alternative preferred in training. An experiment is reported replicating this result and showing that it is not due to generalization of preference levels from training. When the probe is between the two preferred training stimuli, the richer schedule is unpreferred. A SET account of these results is presented which implicates two processes in time allocation: (1) the choice between alternatives based on memory for delays to reinforcement, and (2) the times at which such choices are made. The former process is sensitive to reinforcement scheduling; the latter is sensitive to arousal levels induced by overall reinforcement rates in training.