Evolved navigation illusion provides universal human perception measure

The ability to replicate an experiment across any scientific discipline rests on the assumption that different experimenters are capable of perceiving the same methods and outcomes. However, the large individual differences in experimenters' visual perception undermine this tenet of the scientific process. Further, common devices for measuring similarity in perceptual capacity do not replicate across human groups. Here, we used evolved navigation theory to predict a universal way to measure human perceptual capacity via a distance illusion. We then compared this descent illusion across groups that we selected specifically for their extreme differences: adults in the United States and a group of indigenous Ixil Maya in Guatemala. The descent illusion was indistinguishable across samples. This illusion is among a growing group of evolved illusions capable of comparing subjective human perception across individuals.