The influence of ultraviolet radiation on the pigeon's color discrimination.
Two operant experiments showed pigeons are sensitive to ultraviolet light and treat added UV as a color change, demonstrating that pigeon color vision extends beyond the human visible spectrum.
01Research in Context
What this study did
Researchers tested whether pigeons can see ultraviolet light as a color.
Birds pecked a key when only the UV part of a light changed.
All sessions used single-case design in a lab chamber.
What they found
Pigeons treated UV changes like any other color change.
They did not just react to brightness; they saw UV as a separate color.
The result supports true UV color vision in birds.
How this fits with other research
Davison et al. (1989) later showed reinforcer rate also guides color choices, building on this UV baseline.
Haemmerlie (1983) found narrow wavelength gaps control contrast effects; the 1972 UV work gives the bare-bones proof that pigeons can even see those tiny gaps.
Together the three papers form a chain: birds see UV (1972), wavelength separation matters (1983), and reinforcer frequency fine-tunes choice (1989).
Why it matters
If you run avian labs, treat UV as a real color dimension.
Use UV-reflective stimuli when you want extra discrimination power.
Check your chamber bulbs: standard lights may leak UV and add cues you did not plan for.
Do pigeons see UV light?
Yes. Pigeons have color vision that reaches into the ultraviolet range, unlike humans, whose lenses and cones do not respond to UV. Their retinas include cone types sensitive to short, UV wavelengths.
This means a stimulus that looks identical to a human can look different to a pigeon if it differs in UV content, a difference the bird can use to discriminate.
How the experiments demonstrated UV color vision
In Experiment I, pecking was reinforced on a multiple schedule pairing variable-interval reinforcement with extinction. Two 520-nm stimuli differed only in an added 366-nm ultraviolet component, yet the pigeons responded at clearly different rates.
In Experiment II, pigeons learned a same/different judgment on a split field. Discrimination improved when the UV component was removed from one half, indicating the birds perceived the change as a color change rather than a brightness change.
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Swap one color stimulus for a UV version and see if the bird still pecks accurately.
02At a glance
03Original abstract
Two experiments demonstrated the pigeon's sensitivity to ultraviolet light. In Experiment I, pigeons' responses were reinforced on a multiple schedule with a variable-interval reinforcement schedule in one component and extinction in the other component. Response rates were quite different in the two components where the 520-nm stimuli signalling each component differed only in that one of them contained a 366-nm ultraviolet component. In Experiment II, pigeons were trained to peck one side key when two halves of a split field were of different wavelength and to peck another side key when they were of the same wavelength. Initially, field halves contained both "visible" and ultraviolet components of energy. Discrimination performance improved when the ultraviolet component was removed from one field half. It was argued that the critical change in the stimulus was a color change, rather than a brightness one, or a fluorescence of structures in the pigeon's eye.
Journal of the experimental analysis of behavior, 1972 · doi:10.1901/jeab.1972.17-325