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A Note on the Evolutionary Significance of "Supernormal" Stimuli

J. E. R. Staddon
The American Naturalist
Vol. 109, No. 969 (Sep. - Oct., 1975), pp. 541-545
Stable URL: http://www.jstor.org/stable/2459810
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
A Note on the Evolutionary Significance of "Supernormal" Stimuli
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Abstract

Animals often respond more strongly to extreme (supernormal) stimuli, never encountered in nature, than to the natural stimulus: birds preferentially retrieve extra-large or extra-speckled eggs, for example. An analogous phenomenon in discrimination learning, the "peak shift," suggests that many instances of supernormality may reflect the action of two factors during phylogeny: (a) asymmetrical selection pressure with respect to responsiveness to the relevant stimulus continuum (e.g., size, speckledness), and (b) independent selection pressures limiting the corresponding properties of the natural stimulus.

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