How does a chicken see the world?

What the research shows

The cone set was pieced together over several studies. Bowmaker & Knowles (1977) first measured pigments near 497 and 569 nm in the retina itself; the full four-cone set, with peaks near 415, 455, 508 and 571 nm, comes from later work including Bowmaker et al. (1997) and Hart (2001). One refinement matters for reading the page: the shortest cone is a violet-sensitive type near 415 nm that reaches the near-ultraviolet edge because the lens passes some short-wavelength light, rather than a deep-ultraviolet cone. Each single cone is capped by a coloured oil droplet that tunes it, and Kram, Mantey & Corbo (2010) describe the arrangement of these cells, together with the double cones used for luminance and motion, as the textbook avian cone mosaic.

Temporal resolution was assessed behaviourally. Lisney et al. (2011) found flicker fusion in chickens at around 80–100 Hz and above, beyond the human range; the page uses 87 Hz. That matters for welfare: lighting that looks steady to people can flicker for a chicken. Acuity is less secure, estimated at 6–9 cpd, and the simulation uses 7 cpd. Two limits follow for any screen. A fourth colour dimension cannot be represented with three primaries, so a saturation-boosted image approximates rather than reproduces the chicken's colour space, and a fast flicker-fusion rate belongs to the viewer's eye, which no image can transfer to a human watching it.