Season of birth and morningness: comparison between the northern and southern hemispheres

The present study explored the possible role of the photoperiod at birth on morningness by collecting data in the northern (Italy) and southern (Australia) hemispheres. To assess circadian typology, the Composite Scale of Morningness (CS) was administered to a sample of 1734 university students (977 Italian and 757 Australian; 1099 females and 635 males; age 24.79 +/- 7.45 yrs [mean +/- SD]). Consistent with the literature, females reported higher CS scores (morningness) than males, and Australian participants reported higher CS scores than Italian participants. Allowing for the fact the seasons are reversed between the hemispheres, the results are in line with previous studies. The authors found more evening types were born during the seasons associated with longer photoperiod (spring and summer), and more morning types were born during the seasons associated with shorter photoperiod (autumn and winter), indirectly supporting an imprinting-like phenomenon played by the photoperiod at birth.