Comparative Color Psychophysics

Proper design and interpretation of visual neurophysiology experiments requires understanding the similarities and differences between human vision and animal vision. One approach to this goal is to compare visual performance in humans and animals.

Below are data from one monkey and one human performing a contrast detection task. Upper panels show detection thresholds for a 15 Hz flickering light that was blue or green in interleaved trials. As expected, thresholds increase with retinal eccentricity. This is due to changes in cone density. Less expected is the difference between the monkey and the human blue thresholds. In the monkey, blue thresholds depend weakly on retinal eccentricity. In the human, the dependence is stronger.

To show this difference more clearly, the lower panels show the ratio of blue and green detection thresholds as a function of retinal eccentricity. Monkeys are relatively sensitive to short wavelength flicker. This result has implications for the optical filtering that occurs within the monkey and human eye.

Blue to green threshold comparison