For
Experiment 1a, pupillary responses to different conditions were shown in
Figure 1B. After stimulus onset, the pupil constricted rapidly, exhibiting a typical phasic response to the stimulus presentation. Importantly, pupil constrictions differed between the two conditions, with the irregular stimuli causing greater pupil constriction than the regular stimuli. Based on previous studies (
Mathôt, 2018) and visual inspection of the data from this experiment, we selected the mean pupil size during the pupil constriction period (0.3–1.5 seconds) for statistical analysis. As shown in
Figure 1C, pupil constriction for the regular condition was significantly lower than for the irregular condition, t(23) = 2.55,
p = 0.018, Cohen's d = 0.52.
Experiment 1b replicated the results of
Experiment 1a, pupillary responses to different conditions were shown in
Figure 1E. As shown in
Figure 1F, pupil constriction for the regular condition was significantly lower than the irregular condition, t(23) = 4.53,
p < 0.001, Cohen's d = 0.93. These results suggest that the pupil responds spontaneously to perceived visuospatial regularity. The less regularity, the greater the pupil constriction.