Mental Processing and Distraction

Abstract

The domain of interest of this paper is limited to the continuous performance on simple two-choice reaction time (RT) tasks. It is generally found that the RTs, the RT variance and the error rate Increase over trials. There is no simple explanation for these findings in terms of a speed-accuracy trade-off, nor in terms of some additive factor processing model. Evidently some time gets ’lost’. To tackle this problem the RT was split into two components: processing time and distraction time, which is time spent on other mental activities than those to solve the task. This is the basic assumption of the inhibition theory. This theory is introduced in some length along with its formalisation into some mathematical models and along with the presentation of some empirical evidence. The inhibition theory contains a mechanism that predicts an increase in RTs with time on task. In the experiments of this study a single task condition (the monotonous condition) was contrasted with an alternating task condition (the mixed condition). Whereas most other theories would predict more decrement in RT performance in the more demanding mixed condition, the inhibition theory predicts a larger increase of RTs in the monotonous condition. The results supported the inhibition theory. In the mixed condition the subjects lost less speed over the series of trials, made fewer errors, had lower RT variance and were on the average as fast as in the monotonous condition.

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