What is the Link Between IQ and Sleep?

A study using Creyos (formerly Cambridge Brain Sciences) cognitive tasks has provided new insight into the biological basis of intelligence. Sleep spindles—short neural oscillations that occur during non-rapid eye movement sleep—have previously been linked to IQ test performance. However, there were a few unanswered questions:

• Sleep spindles are also linked with sleep quality, because they protect sleep from external stimuli. Are they only linked with IQ because people who are well-rested tend to do better on cognitive tests?
• As we’ve discussed before, intelligence is not just one thing. If sleep spindles are directly linked with overall intelligence, then which facet, specifically, are they linked with?

The new study, by Fang, Sergeeva, Ray, Viczko, Owen, and Fogel, published in the Journal of Cognitive Neuroscience, sought to answer these questions. They had participants sleep in a lab while physiological data was recorded, including measures of sleep quality and characteristics of sleep spindles. Later in the day, in their homes, participants completed a suite of cognitive tests from CBS Trials (now Creyos).

The main result was that sleep spindles were indeed related to cognitive performance, and the relationship was not mediated by sleep quality. Furthermore, the link was specifically between spindles and reasoning abilities. No links were found with verbal abilities or short-term memory. The results suggest that there is a deep connection between these particular squiggles of brain activity during sleep and “fluid intelligence,” as measured by high reasoning ability. But it’s not just that people with certain spindle patterns sleep better; the boost to reasoning cannot be explained as a side effect of sleep quality.

This is more of a “wow, we really learned something” insight than a “wow, this will change my life” insight, because sleep spindles (like IQ) are relatively stable and, as far as we know, not under our control. Sorry, counting spindles instead of counting sheep probably won’t make you smarter. However, not getting enough sleep means you're probably not performing at your cognitive best.

Because the neural correlates of the Creyos cognitive tasks have already been investigated, the researchers were also able to form hypotheses about the neural underpinnings of the observed effects. See the full paper for the discussion.

As you can see, some of the advantages of Creyos contributed to the success of this study: the tests were pre-made and pre-validated, participants could contribute from home (saving researchers time and money), and past research using the same tests put each result in a more meaningful context.