No consistent correlation between baseline pupil diameter and cognitive abilities after controlling for confounds-A comment on

Baseline pupil diameter does not correlate with fluid intelligence

There has been debate regarding the correlation between baseline/resting state measures of pupil diameter and cognitive abilities such as working memory capacity and fluid intelligence. A positive correlation between baseline pupil diameter and cognitive ability has been cited as evidence for a role of the locus coeruleus-norepinephrine (LC-NE) and its functional connection with cortical networks as a reason for individual differences in fluid intelligence (Tsukahara & Engle, Proceedings of the National Academy of Sciences, 118(46), e2110630118, 2021a). Several recent attempts to replicate this correlation have failed. The current studies make another attempt and find substantial evidence against a positive correlation between pupil diameter and intelligence. Given the data from the current studies in combination with other recent failures to replicate, we conclude that individual differences in baseline pupil diameter should not be used as evidence for a role of the LC-NE system in goal-directed cognitive activity.

Testing locus coeruleus-norepinephrine accounts of working memory, attention control, and fluid intelligence

The current set of studies examined the relationship among working memory capacity, attention control, fluid intelligence, and pupillary correlates of tonic arousal regulation and phasic responsiveness in a combined sample of more than 1,000 participants in two different age ranges (young adults and adolescents). Each study was designed to test predictions made by two recent theories regarding the role of the locus coeruleus-norepinephrine (LC-NE) system in determining individual differences in cognitive ability. The first theory, proposed by Unsworth and Robison (2017a), posits two important individual differences: the moment-to-moment regulation of tonic arousal, and the phasic responsiveness of the system to goal-relevant stimuli. The second theory, proposed by Tsukahara and Engle (2021a), argues that people with higher cognitive abilities have greater functional connectivity between the LC-NE system and cortical networks at rest. These two theories are not mutually exclusive, but they make different predictions. Overall, we found no evidence consistent with a resting-state theory. However, phasic responsiveness was consistently correlated with working memory capacity, attention control, and fluid intelligence, supporting a prediction made by Unsworth and Robison (2017a). Tonic arousal regulation was not correlated with working memory or fluid intelligence and was inconsistently correlated with attention control, which offers only partial support for Unsworth and Robison's (2017a) second prediction.

An examination of relations between baseline pupil measures and cognitive abilities

Examining individual differences in pupil size and pupillary dynamics have revealed important insights into the nature of individual differences in cognitive abilities like working memory capacity, long-term memory, attention control, and fluid intelligence. These findings are often tied to the locus coeruleus-norepinephrine (LC-NE) system, as this system has a tight temporal correlation with pupil diameter. Some recent research has demonstrated positive correlations between resting pupil size and cognitive ability, specifically fluid intelligence. The present study attempted to replicate such relations. Across three studies, a large sample of participants (N = 845) completed batteries of cognitive ability measures and measures of resting pupil size and pupillary hippus (fluctuations in pupil diameter). The cognitive measures comprised tasks previously used to measure attention control, visual short-term memory capacity, fluid intelligence, working memory capacity, and visuospatial ability. At the factor level, cognitive ability and pupil size correlated near zero. We did observe some limited evidence for a negative correlation between resting pupillary hippus and cognitive ability. Given the null findings in the present data, we encourage further replication of relations between resting pupil measures and cognitive abilities before making any strong theoretical conclusions about such relations.

Processing speed, but not working memory or global cognition, is associated with pupil diameter during fixation

Mean pupil size during fixation has been suggested to reflect interindividual differences in working memory and fluid intelligence. However, due to small samples with limited age range (17-35 years) and suboptimal light conditions in previous studies, these associations are still controversial and it is unclear whether they are observed at older ages. Therefore, we assessed whether interindividual differences in cognitive performance are reflected in pupil diameter during fixation and whether these associations are age-dependent. We analyzed pupillometry and cognition data of 4560 individuals aged 30-95 years of the community-based Rhineland Study. Pupillometry data were extracted from a one-minute fixation task. The cognitive test battery included tests of oculomotor control, working memory, episodic verbal memory, processing speed, executive function, and crystallized intelligence. For data analysis, we used multivariable regression models. Working memory and global cognition were not associated with pupil diameter during fixation. Better processing speed performance was associated with larger pupil diameter during fixation. Associations between cognition and pupil diameter during fixation hardly varied with age, but pupil diameter during fixation declined linearly with age (adjusted decline: 0.33 mm per 10 years of age). There were no significant sex differences in pupil size. We conclude that interindividual differences in mean pupil diameter during fixation may partly reflect interindividual differences in the speed of processing and response generation. We could not confirm that interindividual differences in working memory and fluid intelligence are reflected in pupil size during fixation; however, our sample differed in age range from previous studies.