DYNAMICS OF TIME MATCHING - AROUSAL MAKES BETTER SEEM WORSE

Matching of time allocation across alternatives in proportion to relat ive reinforcement rates is a ubiquitous finding in the animal-learning literature on choice. The dynamics of the underlying mechanism, howev er, remain poorly understood. A recent finding by Belke (1992) profoun dly challenges scalar expectancy theory (SET; Gibbon et al., 1988) and other accounts of matching in concurrent variable interval (Vl) sched ules. He studied concurrent probe tests of stimuli associated with equ al VIs but trained in alternative concurrent pairs. Ln training, one w as 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 ge neralization of preference levels from training. When the probe is bet ween the two preferred training stimuli, the richer schedule is unpref erred. A SET account of these results is presented which implicates tw o processes in time allocation: (1) the choice between alternatives ba sed on memory for delays to reinforcement, and (2) the times at which such choices are made. The former process is sensitive to reinforcemen t scheduling; the latter is sensitive to arousal levels induced by ove rall reinforcement rates in training.