3. 4. Pupil diameter
The effect of stress induction on the average pupil diameter (see Figure
4B) was analyzed using a mixed-measures ANOVA with the factors Time
(Ocular 1, Ocular 2, and Ocular 3) and Group (control group vs. stress
group). No significant main effects of Time, F (2, 122) = 2.82,p = .007, \(\eta_{p}^{2}\) = 0.04, or Group, F (1, 61) =
2.36, p = .130, \(\eta_{p}^{2}\) = 0.04 were found. However, the
interaction effect of Time × Group was significant, F (2, 122) =
4.52, p = 0.016, \(\eta_{p}^{2}\) = 0.07. Simple effects analyses
(Bonferroni corrected) indicated that the pupil diameter in the stress
group was significantly larger than that in the control group at the
time point of Ocular 2 (p = .026).
To determine whether the pupil diameter changed during acute stress
induction, an independent sample t-test was performed on the AUCi of
pupil dilation. Significant differences in pupil dilation between the
groups were observed, t (61) = 3.07, p = .003. The result
revealed that calculating mental arithmetic tasks led to a significant
increase in pupil dilation, confirming that pupil diameter varies with
stressful arousal.