No evidence for association between pupil size and fluid intelligence among either children or adults.

Recent studies have investigated resting-state, or baseline, pupil size as a general measure of cognitive abilities, based on the earlier finding that larger pupils might be predictive of higher general intelligence or working memory capacity. However, evidence for such relationships has been mixed, and all previous studies thus far have focused on adult samples. The present study adds to this debate by examining the correlation between fluid intelligence and baseline pupil size in a sample of both children (10 years old) and adults (their parents). Importantly, our sample is representative in terms of socioeconomic background, which was not the case in previous studies, thus addressing concerns about sample selection and variability. We did not find evidence for a relationship of fluid intelligence with baseline pupil size or with pupil-size variability for either children or adults. Therefore, our results do not replicate the relationship between cognitive abilities and baseline pupil size as reported in previous research.