Effect of Morningness-Eveningness Chronotype on Daily and Weekly Fluctuations in Aggression in Preschool Children

Background: the present study aimed at studying the morningness-eveningnesschronotype (mec) of daily and weekly biorhythm fluctuations in the aggressionof preschool children.methods: this was a causal-comparative study. the statistical population was preschool children in tehran. one hundred children were selected through purposive sampling. they were examined at different times of day (08:00, 10:00, 13:00 and 15:00) and different days of the week (saturday, sunday, monday, tuesday and wednesday). the data collection tool used was the mec questionnaire for children, a behavioral questionnaire for preschool children and a self-report questionnaire about aggression. the data was analyzed using mixed anova. results: the results showed that the aggressive behavior of pre-school children in the educational environment varies throughout the day and week. also, the aggressive performance of preschool children in the morning differed from that of mid-session children or evening-type children in the educational environment during the week (p<0.01). conclusion: the results of the behavioral questionnaire showed that the effect of the group on the level of aggression was not significant, but the effect of the day of the week and time of day was significant.