Test-retest reliability of free visual exploration and split-field pupillometry in the assessment of pseudoneglect

Pseudoneglect, a subtle leftward bias in spatial attention observed in neurologically healthy individuals, is commonly investigated using behavioural measures with established test-retest reliability. However, the test-retest reliability of recently developed eye-tracking and pupillometric measures of pseudoneglect has not been yet established. The present study examined the reliability of two objective indices of pseudoneglect: early horizontal gaze deviation during free visual exploration (FVE) and spatial bias in the pupil light response measured with split-field pupillometry. Thirty-one healthy adults were recruited for a three-session study. Bayesian hierarchical models were used to quantify reliability using intraclass correlation coefficients (ICCs) and trial-level varying ICCs (vICCs). Reliability analyses indicated good single-session reliability and excellent reliability for scores averaged across sessions. Trial-level vICC analyses further showed that aggregated horizontal gaze deviation provided reliable participant-level estimates, although measurement precision varied across individuals. In contrast, the space-relative pupil bias score exhibited uninformative reliability. These findings indicate that early horizontal gaze deviation during free visual exploration is a reliable measure of individual differences in pseudoneglect and is suitable for repeated-measures and correlational research. In contrast, split-field pupillometry appears poorly suited for assessing stable individual differences in spatial attentional bias under the present conditions.