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by Satoshi Kanazawa



Some people are night owls, and others are morning larks.  What makes the difference may be their levels of general intelligence.


Virtually all species in nature, from single-cell organisms to mammals, including humans, exhibit a daily cycle of activity called circadian rhythm.  The circadian rhythm in mammals is regulated by two clusters of nerve cells called the suprachiasmatic nuclei (SCN) in the anterior hypothalamus.  Geneticists have by now identified a set of genes that regulate the SCN and thus the circadian rhythm among mammals.


However, humans, unlike other mammalian species, have the unique ability, consciously and cognitively, to override their internal biological clock and its rhythmic outputs.  In other words, at least for humans, circadian rhythm is not entirely a matter of genetics.  Within broad genetic constraints, humans can choose what time to go to bed and get up.  Humans can choose to be night owls or morning larks.


While there are some individual differences in the circadian rhythm, where some individuals are more nocturnal than others, humans are basically a diurnal (day-living) species.  Humans rely very heavily on vision for navigation but, unlike genuinely nocturnal species, cannot see in the dark or under little lighting, and our ancestors did not have artificial lighting during the night until the domestication of fire.  Any human in the ancestral environment up and about during the night would have been at risk of predation by nocturnal predators.


Read in Full:  http://www.psychologytoday.com/blog/the-scientific-fundamentalist/201005/why-night-owls-are-more-intelligent-morning-larks



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