Free-Choice by the Rat of the Greater of Two Brightness Changes

Abstract

In a previous experiment (2) it was shown that rats will choose that arm of a maze the brightness of which has been changed between an exposure trial and a free-choice trial. The present experiment tests the hypothesis, derivable in part from Glanzer's satiation theory, that if both arms are changed, rats will choose the arm representing the greater change. Ss were 28 male albino rats satiated for food and water. Four stimulus conditions were used, a condition being composed of two trials: on Trial 1 rats were exposed to 2 arms of a Y-maze for 3 min., but were prevented from entering either by means of glass partitions; for Trial 2 the brightnesses of both arms were changed and the partitions removed. In Condition I, the Trial 1 configuration was left-black, right-grey; on Trial 2 both arms were white. In Condition II, on Trial 1 the configuration was left-grey, right-black, and again on Trial 2 both arms were white. Conditions III and IV were analogous to I and II with white and grey on Trial 1, and both arms black on Trial 2. Of the 28 Ss, 20 made the predicted response, significant by the sign test (one tail) at better than the .02 level. Errors were distributed equally between Conditions I and II combined and III and IV combined, indicating that the grey arm was discriminable from both the white and black arms.