Evidence for environment hypothesis: Cross-cultural measurement invariance of the composite scale of morningness across Bangladesh and Spain.

Morningness-eveningness reflects individual differences in circadian functioning and is related to health and well-being. Cross-cultural comparison could facilitate understanding of the environmental factors affecting morningness-eveningness, which requires establishing cross-cultural validity of the relevant assessment tools. In this study, we applied the Composite Scale of Morningness (CSM) to Bangladeshi ( = 1015; 37.9% women) and Spanish ( = 1054; 73.2% women) university students (aged 18-27 years) to evaluate alternative factorial models of the CSM and to test its measurement invariance across cultures. Moreover, this study tested environment hypothesis, suggesting that higher average temperatures and lower latitudes would be related to greater morningness. From nine competing factorial models, a bifactor model with two specific factors (morning preference and morning affect) showed the best fit for both cultures. The two-factor bifactor model had full metric invariance with partial scalar and strict invariance across cultures. The Bangladesh-Spain comparison of the CSM scores revealed higher morningness in Bangladeshi students which supports the environment hypothesis. Overall, this research confirms that morningness-eveningness construct is perceived and interpreted similarly by the Bangladeshi and Spanish students. Importantly, this study highlights the effects of environmental factors including latitude and temperature on morningness-eveningness, and thus facilitates further cross-cultural morningness-eveningness research.