Dark adaptation in the pigeon.

Abstract

Anew method for studying dark adaptation in the pigeon is described. Birds are trained to peck one key when a stimulus patch is lighted and another key when the patch is dark. The keys were arranged in such a fashion that the bird''s responses controlled the luminance of the patch in approximation to the bird''s absolute threshold. Records of stimulus luminance throughout the length of an experimental session thus measured the course of dark adaptation. Birds were preexposed to 2 different levels of illumination for various times, and to a red stimulus at the higher intensity. Results indicated a 2-segment dark adaptation curve similar in general form to that for the human, although the cones contributed proportionately more to sensitivity than is the case in the human curves. Dark adaptation for the red patch showed the initial segment of the curve, with little change in threshold thereafter. 15 references.