Psychomotor testing of on-call anaesthetists.

The critical flicker fusion frequency and choice reaction times of 16 on-call anaesthetists were measured between 1400 and 1600, at 2300 and at 0200 hours. Critical flicker fusion decreased between the afternoon and 2300; there was no further change between 2300 and 0200. No significant differences in choice reaction times were found on any of these different occasions.