Morningness-eveningness and the environment hypothesis - A cross-cultural comparison of Turkish and German adolescents.

Individuals differ in morningness-eveningness, which is their preferred time for intellectual and physical activities. Although it is a basic human trait, cross-cultural comparisons are scarce but interesting because they help to determine the influence of exogenous factors, such as ambient temperature, climate and photoperiod. We here compare a large sample of German and Turkish adolescents (N = 26 465) by using the Composite Scale of Morningness and the Morning Affect Factor. First, we show that the Morning Affect Factor and Morningness scores are equivalent in both countries and we report country differences with Turkish adolescents scoring higher on morningness (F1,26 038 = 1293.313, p < 0.001) and in the morning affect (F1,26 038 = 133.833, p < 0.001). This fits into the environment hypothesis suggesting that populations near the equator should be more morning oriented. Meanwhile, gender differences were small and adolescents showed a lower morningness and a lower morning affect with increasing age.