A study of tracking performance during auditory distraction

Abstract

The distraction of attention by irrelevant information is normally considered to have determinantal effects on human performance, but published accounts have provided only limited evidence. This study examined the effects of auditory distraction on the execution of a visual compensatory tracking task. It was hoped that a sensorimotor task demanding such information-processing capacity would create appropriate conditions for the detection of distraction effects.

In order to establish a suitable tracking requirement, an adaptive task was designed. Its purpose was to impose a heavy mental workload without the task becoming uncontrollable. To achieve this, the tracking forcing function bandwidth was adjusted by computer throughout the task in response to measured changes in the operator’s error. Observation confirmed that the procedure provided a substantial workload throughout practice. The adaptive task was used in subsequent experiments as a training aid and as a method for determining the optimum tracking load for each subject.

Three experiments compared tracking performance during auditory distraction to performance in nondistracted conditions. Random presentations of moderate intensity (82 dBA) bursts of white noise resulted in increased RM8 error and increased tracking response delay during the few seconds following noise onset. The affects were highly localised and were very shortlived, surviving only a few exposures. The magnitude of effect was also influenced by the neighbouring forcing function dynamics. Distraction effects were greatly reduced in noise presentation followed a predictable periodic schedule. When randomly presented verbal messages were used as distractors instead of noise, the increase in tracking error was not so localised and subjects did not adapt to distraction so quickly.

Because periodicity had so noticeably promoted adaptation a final experiment investigated the formation of temporal expectancy during tracking. Subjects were asked to predict when intermittent auditory signals would occur. It was found that subjects anticipated temporal events readily, probably using a rational strategy, and that they forced expectancies in very similar fashion whether or not they were tracking. The relative insensitivity of expectancy formation to a simultaneous tracking load (and vice versa) was in accord with the broad suggestion that temporal expectancy could participate in the adaptation process.

This study corroborated reports that distraction effects are generally variable, task-dependent, and of short duration. It is proposed that auditory distractors affect tracking performance in a direct way by commanding selection and analysis, and sometimes indirectly by altering arousal. Even so, tracking is probably not a very susceptible task. The explanations for this suggest that tracking tolerates discontinuities in information sampling and in motor processing rather better than has often been supposed, and that this -- in combination with the often very brief timescale of the distraction effects – affords tracking some immunity from distraction. Also, it seems likely that expectancies of various sorts, including temporal expectancy, mediate the effects of distraction. Following this interpretation, distractibility should be seen as a contributor to normal attentional functioning, because it can provide information to assist in the formation of predictive internal models to guide selection.