Applying the scalar timing model to human time psychology : Progress and challenges

Abstract

Scalar timing (or scalar expectancy) theory, SET, was originally developed as an explanation of the performance of animals on temporally-constrained reinforcement sched- ules. In the last decade, however, it has had a growing influence on the study of human tim- ing, and may now even be the dominant approach. The present paper reviews its successes, and points to some challenges for the future. Among the successes are (1) a re-invigoration of the old idea that some aspects of timing in humans depend on an “internal clock,” (2) the provision of a framework for developmental studies of timing in humans (both of children and the elderly), (3) the development of precise quantitative models of timing in humans, which depend on an interaction of clock, memory, and decision processes. In spite of these successes, however, many problems remain. Some of these concern details of how the SET system itself works, particularly questions concerning the roles of memory and decision processes. Data from recent experiments which manipulate memory and decision mecha- nisms in the SET model, in an attempt to clarify their operation, will be presented. Another set of problems concerns the application of SET-related ideas to “classical” timing tasks such as production, reproduction, and verbal estimation. Behavior on this “classic trio” of tasks often seems at variance with the scalar model, but it will be shown that the incompatibility may be more apparent than real, and that SET-based models may be used to explain many aspects of performance on these classical tasks. Thus, not only can SET-based models ac- count for recently-collected data on many timing tasks, but they may be able to provide the first rigorous models of behavior on procedures known for more than 150 years. Introduction