Abstract

TIME OF DAY, SPEED-ERROR TRADE-OFF, AND THE ENCODING OF NEW INFORMATION IN CHOICE REACTION TIME TASKS

ABSTRACT

Background: It is well established that human performance varies with the time of day. The pattern of diurnal variation depends on the type of task performed. Responses in simple reaction time tasks are usually faster later in the day. In search tasks, there is often a speed-error trade-off, with responses later in the day being faster but less accurate. This was examined here, and the study also measured the speed of encoding in the morning and afternoon. Method: Ninety-six university students participated in the study. They each completed the tasks in the late morning (11.00-12.00) and afternoon (15.00-16.00). Half the participants carried out the sessions in the morning and then in the afternoon, and the others in the reverse order. The two test sessions were on separate days. Participants carried out a focused attention two-choice reaction time task and categoric search tasks. The outcomes of interest were mean reaction times, errors and the speed of encoding new information (alternations-repeats). Cardiovascular measures were also taken to confirm physiological changes over the day. Results: Heart rate decreased over the day, and blood pressure increased. Reaction times in the focused attention task were quicker in the afternoon, and the speed of encoding new information was also quicker. The categoric search tasks showed a speed-error trade-off, with performance being faster but less accurate later in the day. Significant differences were found between the different types of categoric search tasks, but these did not interact with the time of day. Conclusion: The present study confirmed the changes in cardiovascular function found over the day. The search tasks also replicated the speed-error trade-off, with performance in the afternoon being faster but less accurate. The performance of the focused attention task was quicker in the afternoon, and this was associated with faster encoding of new information.