Fine Tuning the Timing in the Sequential Reaction Time Task

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One of the essential characteristics of human action is that people constantly carry on two or more overlapping behavioral sequences simultaneously. For most the part, such actions are based on well-learned and smoothly run behavioral repertoires. We drive a car, carry on conversations, and manage not to collide with others who are doing the same thing. However, when attentional resources are diverted to one of these tasks, perhaps the conversation becomes deeply personal or highly emotional or a pelting storm makes driving hazardous, the other behavioral actions become error prone, slow down dramatically, or even cease altogether. Exactly what takes place during these periods where processing resources must be diverted is complex and only partly understood. This research will explore the impact that introducing a secondary task has on performance of the primary task and will examine the temporal relations between the two. The primary task will be one in which individuals must learn the order of a complex sequence of events, such as a series of lights appearing in any of several physically separate locations on a computer monitor. The secondary task will consist of a series of tones of varying pitch, where the participants will be required to keep a running count of how many tones of a particular pitch occurred. Recent experimental results have shown a surprising but critical relationship between exactly when an individual responds to the primary stimulus and when the secondary event occurs. Specifically, the closer together in time the two occur, the less disruptive the secondary stimulus is, provided that a successful response has already been made to the primary stimulus. The implication of this finding is that the secondary task doesn't disrupt performance simply because it is a "secondary" task. The degree to which performance is compromised is directly related to the difficulty of each task, to the amount of time it takes to process each stimulus and respond to it, and critically related to the temporal relationships between the two. The experiments will explore in detail these temporal relationships and use the results to test a variety of theoretical models of human performance. As is clear from a moment's reflection on just what takes place in a wide variety of work place settings, from assembly-line workers to airline pilots, these seemingly mundane issues are of critical importance. Understanding and learning how to fine-tune the timing between tasks in these multiple-tasking settings will go a long way toward increases in safety and performance.