Interindividual Differences in Diurnal Variations in Alertness, Performance, and Adrenaline Excretion

Abstract P átkai , P. Interindividual differences in diurnal variations in alertness, performance, and adrenaline excretion . Acta physiol. scand. 1971. 81 . 35–46. Subjects classified as habitual morning vs. evening workers on the basis of their answers to a questionnaire, were compared with regard to day‐time variations in catecholamine excretion and performance. Adrenaline excretion in morning workers was highest in the morning and decreased gradually during the day, while evening workers showed nearly constant excretion values. The performance of morning workers did not vary during the day, while evening workers showed a steady improvement, performing best in the evening. In addition, a significant difference between the two groups was found in the personality dimension of extraversion‐introversion, showing that evening workers were more extravert and morning workers more introvert. The constancy of individual diurnal rhythms and their relations to personality traits, are discussed.