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

## TL;DR

This study found no link between pupil size and fluid intelligence in children or adults, contradicting earlier research.

## Contribution

The study is the first to examine this relationship in children and includes a representative socioeconomic sample.

## Key findings

- No correlation found between fluid intelligence and baseline pupil size in children or adults.
- Pupil-size variability also showed no association with cognitive abilities.
- Results contradict previous findings and suggest the relationship may not be reliable.

## Abstract

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.

The online version contains supplementary material available at 10.3758/s13423-025-02644-2.