Abstract
In order to study the existence of ultradian rhythms in human performance, reaction times and omissions of responses to signal stimuli were registered from 17 subjects performing a selective auditory attention task, at 15–minute intervals from 9:00 am to 3:00 pm. The task consisted of selectively focussing attention, first to the left and then to the right ear, and pressing a button every time a signal stimulus was detected. Rhythmometric analysis showed the existence of significant (p<.05) ultradian rhythms both in the temporal course of the reaction time and in the number of omissions of responses to signal stimuli. Results are discussed in terms of the level of difficulty of the task and the processing resources involved.