Time-of-Day Effects in Performance by Seventh Grade Students on Two Measures of Impulse Control

Abstract

This study examined differential performance of 52 boys and 52 girls in Grade 7, who were randomly assigned to morning and afternoon groups and administered two tasks of impulse control on Tuesdays one week apart. Selected measures of impulse control were tasks of delayed reward choice, modeled after Mischel's technique and estimation of a 60-sec. interval. Larger overestimations of time and fewer delayed choices by students tested in afternoons were predicted on the basis of circadian effects of increase in body temperature. Consistent with prior research, as cited by Maccoby and Jacklin (1974), boys and girls were expected to perform equally well on both tasks. Analysis of variance yielded no differences between morning and afternoon groups. Girls tended to manifest predicted circadian effects more than boys, tended to make fewer delayed reward choices than boys, and made less accurate time estimations than boys.