Research examining various psychological correlates of circadian type (also known as diurnal preference) has been, over the years, quite expansive. A notable omission within this research program would appear a systematic exploration of the relation between intelligence and morningness–eveningness. The present study redressed this imbalance. 420 participants performed two self-report inventories assessing circadian type, as well as measures of intelligence from two psychometric batteries: CAM-IV and the ASVAB. The results indicate that, contrary to conventional folk wisdom, evening-types are more likely to have higher intelligence scores. This result is discussed in relation to current theories concerning the nature of human cognitive abilities.
The 1999 study: Morningness-eveningness and intelligence: early to bed, early to rise will likely make you anything but wise! by Roberts RD and Kyllonen PC, Dept. of Psychology, University of Sydney, Australia - via Barking up the wrong tree