ALT Across 17 studies, the meta-analysis shows moderate evidence against an effect of taVNS on pupil dilation. A: Contour-enhanced funnel plot showing standard error and observed outcome for each included study, grouped by stimulation type. Studies applying continuous (tonic) stimulation are depicted in pink, while studies applying pulsed (phasic) stimulation are depicted in green. B: Bayes factor (BF, log-transformed) robustness plot. BF are plotted across prior distributions differing in their width. The plot shows moderate evidence for H0 across all studies (in black). After grouping by stimulation type, we find strong evidence for H0 for continuous stimulation (in pink) and moderate evidence for H1 for pulsed stimulation (in green). C: Forest plot of all included studies, showing no effect across all included studies (mean = 0.14, CI [0.01, 0.27] for taVNS compared to sham. D: We assessed the risk of bias for all studies using a standardized checklist.