Parallel processing in overlapping tasks: A model and a method

Abstract

A dual-bottleneck model for parallel performance of reaction-time tasks in the psychological refractory period paradigm was developed. The first, preparation-based bottleneck prevents perceptual and decisional processes in the second task from operating in parallel with the first task when these processes require specific and explicit preparation. The second bottleneck prevents two independent responses from being initiated and executed in arbitrarily close succession, with the effective strength of this bottleneck depending on response similarity. The response-initiation bottleneck was manipulated in a series of experiments to demonstrate that this bottleneck is responsible for many of the underadditive interactions in overlapping-task performance that have previously been held to indicate parallel processing. A new method was developed to assess the extent and nature of parallel processing in overlapping tasks more reliably and in more detail. This method may also provide an important tool in the investigation of the adaptive control of human information processing.