Do normal pupil diameter differences in the population underlie the color selection of #thedress?

The fundamental question that arises from the color conundrum of #thedress is “What are the phenomena that underlie the individual differences in the reported colors when all other conditions like light and device for the display are identical?” A survey of 384 participants showed near-equal distribution into blue/black (b/b) and white/gold (w/g) groups. We looked at pupil size differences in a sample population of 53 individuals from these two groups and a group that switched from w/g to b/b. Our results showed that the w/g and switch groups had significantly lower pupil size than the b/b group (w/gpupil size. A standard infinity focus experiment was then conducted on 18 participants from each group to check if there is bimodality in the population, and we found a statistically significant difference (w/gpupil size by 3–4 mm, but the participants did not report a switch. The results suggest a population difference in normal pupil size influencing color observation which was exposed by the dress.