Adolescents in high school suffer from circadian misalignment, undersleeping on weekdays and oversleeping on weekends. Since high schools usually impose early schedules, adolescents suffer from permanent social jetlag (SJL) and thus are a suitable population to study the effects of SJL on both academic and cognitive performance. In this study, 796 adolescents aged 12-16 years reported information about their sleep habits, morningness-eveningness (M-E), cognitive abilities and grade point average (GPA). Time in bed on both weekdays and weekends was not related to cognitive abilities, and only time in bed on weekdays was related to academic achievement. SJL was negatively related to academic achievement, cognitive abilities (except for vocabulary and verbal fluency abilities) and general cognitive ability (g), whereas M-E was slightly positively related to academic achievement and marginally negatively related to inductive reasoning. Results separated by sex/gender indicated that SJL may be more detrimental to girls' performance, as it was negatively related to a greater number of cognitive abilities and GPA.

Measuring morningness–eveningness is an important aspect of individual differences because it is associated with many aspects of personality and health. The present study outlines recent advancements in the field of measurement and proposes an improved assessment of morningness–eveningness, such as the measurement of circadian amplitude, updating and reflecting new item developments, addressing the clock time based measures, the morning-biased items and the aspect of uni versus multidimensionality. Four studies have been carried out in Germany to present a novel development (with a total sample of N = 1181). In study I, the exploratory factor analysis (EFA) revealed three dimensions, one of morningness, one of eveningness and one of amplitude/stability. Then, items were reduced to present a clearer factor structure by removing ambiguous items. In the second study, a shortened questionnaire was applied, with 15 items (5 per construct), but Confirmatory Factor Analysis (CFA) did not provide acceptable fit indices. Refining items were made in study III, which again showed a clearer factor structure in EFA, and subsequently, in study IV, the refined set of 15 items provided a good fit of a CFA. The final questionnaire was tested for validity by applying clock times, personality questions and alertness ratings. Thus, this newly developed questionnaire contains three distinct dimensions. To reflect the new content, the scale is labelled morningness–eveningness-stability-scale improved (MESSi).

Adult men (n = 582) and women (n = 765) from six nations (Spain, Peru, Venezuela, the United Kingdom, Australia, and the United States) completed two reliable and valid measures of chronic procrastination. Because both arousal and avoidant procrastination types were significantly related across the entire sample (r = .72, p < .001) and within each national sample, regression analyses calculated “pure” arousal and “pure” avoidant procrastinators, controlling for the scale scores of the other scale. Results indicated no significant sex or nationality differences within and between nations on self-reported arousal or avoidant procrastination. Overall, 13.5% and 14.6% of men and women self-identified as either arousal or avoidant procrastinators, respectively. These findings suggest that the tendency toward frequent delays in starting or completing tasks may be prevalent across diverse populations in spite of their distinct cultural values, norms, and practices.

Individuals differ in their timing of sleep (e.g., bedtimes, rise times) and in their preference for morning or evening hours. Chronotype refers to these differences in morningness—eveningness. Ado...