Investigation of morning–evening orientation in six countries using the preferences scale

Morningness, or the preference for morning or evening activities, is an individual difference in circadian rhythms with potential applications in optimizing work schedules, sports performance, and academic achievement. This study addressed some neglected issues in morningness research. First, we propose a morningness self-report measure, the Preferences Scale, to remedy deficiencies in existing scale content and format. Second, because little is known about group or population differences in morningness, we collected data from university students in six countries. Both classical and structural equation modeling (SEM) analyses indicated that the psychometric properties of the Preferences Scale are adequate and comparable with an established morningness instrument, the Composite Scale. The SEM analyses also showed considerable group consistency in the morningness construct. However, mean differences were found across countries, suggesting that people in more temperate climates perceive themselves to be more morning-oriented than their peers in less temperate climates.