Experimental Studies of Shift-Work III: Stabilized 12-hour Shift Systems

Twenty-two subjects took part in an experiment to determine whether the relationship botween efficiency at mental tasks and the circadian rhythm of body temperature observed in two earlier studios was affected by an increase in the length of the duty spoil from S to 12 hours. Subjects wore assignod either to a control ‘ day ‘ shift (0800-2000) or a ‘ night‘ shift (2000-0800), and woro tested for a period of 12 consecutive days on the same shift. Some signs of fatigue duo to the oxeessive length of the duty-spell wero observed, but an underlying relationship between temperature and performance remained in evidence in some scores throughout the trial period. Adaptation of temperature rhythm to work on the night shift was only partial, and less marked than in a previously studied ' night ' work situation; the partial adaptation was nevertheless relatively closely reflected in the recorded performance trends. It was concluded that the rosults obtained in the present and previous studies in this series demonstrated that, within certain limits, the relationship between temperature and efficiency was sufficiently marked to warrant further research into its generality.