DEVIATIONS FROM MATCHING AS A MEASURE OF PREFERENCE FOR ALTERNATIVES IN PIGEONS

Preferences for larger or smaller formally defined response classes were investigated in a concurrent schedule procedure. Twelve pigeons were run on a series of concurrent variable‐interval reinforcement schedules, from which baseline matching functions were obtained. An experimental phase followed, in which a second response key was available in one concurrent schedule alternative. For half the birds, the second key was programmed identically with the first; for the other half, the added key was programmed for extinction, with position irrelevant. Comparison of baseline and experimental matching functions revealed no systematic changes in either slope or intercept for birds in the latter group. Systematic shifts in function intercepts in the former group indicate a response bias toward the response‐constrained (single‐key) schedule alternative. Although contrary to the literature of preference for choice, this finding may be interpretable through an account dealing with imposed variability of responding.