PREFERENCE BETWEEN VARIABLE-RATIO AND FIXED-RATIO SCHEDULES - LOCAL AND EXTENDED RELATIONS

Although it has repeatedly been demonstrated that pigeons, as well as other species, will often choose a Variable schedule of reinforcement over an equivalent (or even richer) fixed schedule, the exact nature o f that controlling relation has yet to be fully assessed. In this stud y pigeons were given repeated choices between concurrently available f ixed-ratio and variable-ratio schedules. The fixed-ratio requirement ( 30 responses) was constant throughout the experiment, wheareas the dis tribution of individual ratios making up the variable-ratio schedule c hanged across phases: The smallest and largest of these components wer e varied gradually, with the mean variable-ratio requirement constant at 60 responses. The birds' choices of the variable-ratio schedule tra cked the size of the smallest variable-ratio component. A minimum vari able-ratio component at or near 1 produced strong preference for the v ariable-ratio schedule, whereas increases in the minimum variable-rati o component resulted in reduced preference for the variable-ratio sche dule. The birds' behavior was qualitatively consistent with Mazur's (1 984) hyperbolic model of delayed reinforcement and could be described as approximate maximizing with respect to reinforcement value.