STIMULUS EFFECTS ON BEHAVIOR ALLOCATION IN 3-ALTERNATIVE CHOICE

Six pigeons were trained on three-alternative concurrent variable-inte rval schedules that were available through a snitching response and we re signaled by colored stimuli. The discriminative stimuli for two of the schedules were always 560 nm and 630 nm, but the stimulus signalin g the third alternative was varied across conditions over seven levels between these colors. For each third-alternative stimulus condition, the relative frequency of reinforcers was varied over three conditions with 4:1 and 16:1 reinforcer ratios between each pair of alternatives . The distribution of responses between the alternatives was dependent jointly on the third-alternative reinforcer rate and on the disparity between the stimulus signaling the third alternative and those signal ing the other alternatives. A generalized matching approach was unable to provide invariant measures of the discriminability between constan t stimuli, but a contingency-discriminability approach provided excell ent fits and sensible and invariant stimulus discriminability measures .