Data for three fundamental psychophysical functions (spatial modulation sensitivity, temporal modulation sensitivity, and increment-threshold spectral sensitivity) were compared for groups of 12 rhesus monkeys and 12 human subjects. It was found that there are important, nontrivial differences between the data for monkeys and humans, but that many of the differences could be accounted for by structural or passive differences in the visual systems. Therefore, it was concluded that the neural processing of information along the visual pathways of the two species is generally similar and that the monkey is an excellent model of the human visual system.