Color vision in the spider monkey (Ateles).

Spectral sensitivity and color vision were investigated in 2 spider monkeys (Ateles) using a forced-choice discrimination paradigm. The increment-threshold spectral sensitivity functions of both animals were very similar to those of normal human trichromats; all had three regions of peak sensitivity located at 440-460, 520-540, and 670-620 nm. However, color vision tests (neutral point, anomaloscope, and wavelength discrimination) indicated that at least two qualitatively different types of color vision exist among spider monkeys. The female tested had essentially normal trichromatic color vision (although her anomaloscope match was shifted slightly in the deutan direction) with acute wavelength discrimination. The male, however, was clearly a protanomalous trichromat. He required much more red light in a red/green mixture to match a standard yellow than did normal trichromats. This variation in color vision is discussed in the context of an analogous variation known to exist among other South American monkeys.