People with higher IQs tend to prefer going to bed later at night and getting up later in the morning.
The conclusions come from a study of adolescent bedtimes and their adult IQ.
Researchers found that on a weekday the ‘very bright’ adolescents went to bed at 12:29 am and got up at 7:52 am, on average.
In contrast, the ‘very dull’ went to bed at an average of 11:41 pm and woke up at 7:20 am, on average.
At the weekend, when people have more latitude to follow their own rhythms, the differences were even more obvious.
The study’s authors explain the average times:
‘‘Very dull” individuals on average go to bed at 00:35; ‘‘dull” individuals go to bed at 01:03; ‘‘normal” individuals go to bed at 01:13; ‘‘bright” individuals go to bed at 01:25; and ‘‘very bright” individuals go to bed at 01:44.”
Bear in mind that all these times are for adolescents, who tend to sleep for longer than adults.
For adults, the equivalent times would probably by earlier as adults tend to have less freedom and they sleep for shorter periods.
Adults who naturally go to bed after 11pm and rise after 8pm would be considered night owls.
The study’s authors explain the link by referencing our evolutionary past.
Tens of thousands of years ago it would have been natural to go to bed earlier and get up earlier.
Going to bed late, though, would have been ‘evolutionary novel’.
In other words, as people have evolved and become more intelligent, they have also tended to stay up later.
Nocturnal activities are a relatively modern invention in evolutionary terms.
Whether or not this explanation is true is highly debatable (see Dutton, 2013), but the link between IQ and sleeping later exists nevertheless.
The study was published in the journal Personality and Individual Difference (Kanazawa & Perina, 2009).