Figure 4.
Pupil diameter in monkeys. Pupil diameter in monkeys followed the image rate at 2 Hz in the random (blue) and the structured (orange) conditions, but the pair rate at 1 Hz was only evident in the structured condition (structured vs random: monkey P: t(31) = 10.37, p < 0.001, g = 3.524; monkey C: t(41) = 2.327, p = 0.025, g = 0.731). The inset show a zoomed-in version of the power spectrum at ∼1 Hz. Peaks at 3 and 4 Hz likely reflect harmonics of the 1 and 2 Hz response, respectively. Shading represents the SEM across sessions. Asterisk indicates statistical significance at p < 0.05 for the contrast structured vs. random condition.