IRIS PIGMENTATION AND COMPARATIVE PSYCHOLOGY
Annotated Bibliography: Simple reaction time, hearing loss from exposure to loud noise, hypertension, feeding behavior of song birds, and hunting tactics of predators are all related to differences in iris pigmentation.
Eye Colors for 5620 Species
(Each also rated on a ^ 5-pt. scale ^ of eye-darkness)
Eye Color and Animal Behavior
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Puzzles
The content for this site is written by Morgan Worthy.
Email: mworthy@comcast.net
Hale, B.D., Landers, D.M., Snyder-Bauer, R. and Groggin, N. (1980) Iris pigmentation and fractionated reaction and reflex time. Biological Psychology, 10, 57-67.
In a series of seven well-controlled studies, they demonstrated that dark eyes in humans, independent of race or skin color, are associated with the ability to make quick (simple, not choice) reactions to visual or auditory stimuli.
A meta-analysis of all seven studies was reported, “Using a z- transformation procedure, a z value was obtained that could not occur by chance any more than one time in 10 million. Worthy’s hypothesis, therefore, reliably predicts reaction time differences between eye color groups from one study to the next.” p. 61
Craig, A.J.F.K. and Hulley, P.E. (2004) Iris colour in passerine birds: Why be bright-eyed? South African Journal of Science, 100, 584-588.
Eye colors for 1143 species of passerine birds were classified as Pale, Red or Brown. These species eye colors were then tested for correlation with various other species traits within each of ten family-level groups. Most of the significant findings (29 of 36) were in the five families with most diverse eye colors. A flavor of the many findings can be given with two quotations that deal with feeding behavior:
Corvini (crows): “A coloured iris [Pale or Red] is present in close to 50% of the woodland and forest corvids, but is exceptional (one species) in birds of open grassland and thus the association of a coloured iris with feeding in vegetation and a dark iris with ground feeding is clearly closely linked to habitat preferences.” (p. 586)
“The broad feeding categories used in our analysis are not an adequate test of Worthy’s proposal. However, a dark iris was correlated with ground feeding in three groups (Corvini, Malaconotinae and Ploceidae), whereas the ground-feeding Sturnini were mostly pale-eyed.” (p. 587)
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