Rhythms in Human Performance: 1 ½-Hour Oscillations in Cognitive Style

Abstract
Performance on verbal and spatial matching tasks was assessed every 15 minutes for 8 hours. Significant 90- to 100-minute oscillations were observed for each task. These oscillations were 180° out of phase, supporting the hypothesis that in humans the basic rest activity cycle involves alternating activation of processing systems residing in the two cerebral hemispheres.