Intelligence predicts better cognitive performance after normal sleep but larger vulnerability to sleep deprivation

It has been proposed that intelligence allows some people to cope better with stress than others. However, whether those with higher intelligence are also more resilient to the cognitive effects of insufficient sleep remains unclear. Participants (N = 182) were randomized to either a normal night of sleep or a night of total sleep deprivation. The Raven's Standard Progressive Matrices Test set E was used to estimate fluid intelligence prior to the experimental night. A sleepiness measure and a cognitive test battery were completed at 22:30h (serving as the baseline session for both groups), and the following day at 08:00h, 12:30h, and 16:30h after sleep manipulation. As per preregistration, sleepiness and measures of arithmetic ability, episodic word memory, simple attention, and spatial working memory were analyzed. At baseline, higher fluid intelligence was associated with fewer errors and faster calculations on the arithmetic test, and fewer episodic memory errors, but was not associated with spatial working memory performance, simple attention, or sleepiness. Sleep deprivation led to larger impairments in those with higher fluid intelligence, evident for arithmetic ability, episodic memory, and a trend for spatial working memory. Fluid intelligence did not predict vulnerability on any of the other tests or sleepiness. These data indicate that fluid intelligence is related to superior higher-order cognitive functioning under optimal sleep condition, but it does not protect against the deleterious cognitive effects of insufficient sleep. Further studies may test whether the cognitive benefits of intelligence are primarily limited to optimal situations.