Abstract
Pigeons were studied in an experiment involving two concurrently available response keys. Conditions were such that in the first condition the predictions of melioration (Herrnstein & Vaughan, 1980), minimization of deviation from matching, and maximization were identical: relative time on the right key should have fallen between .125 and .25, which in fact occurred. In the second condition, melioration predicted a shift in relative time on the right to between .75 and .875, which would involve a transient deviation from matching as well as a substantial drop in rate of reinforcement. All three birds eventually shifted their distribution of behavior to within the range predicted by melioration.