Sequences of Fixed-Ratio Schedules: The Relative Effects of Reinforcer Magnitude and Ratio Size in the Second Fixed Ratio

Abstract

Four pigeons were given a choice between two sequences of fixed-ratio schedules. The second fixed ratio was a fixed-ratio 5 followed by 2-s access to grain in one sequence and a fixed-ratio 45 followed by 8-s access to grain in the alternative. In Phase 1, the initial fixed-ratio schedules of each sequence, which were always equal, varied from fixed-ratio 1 to fixed-ratio 50. At each initial fixed-ratio value, 3-s access to grain and a 0.25-s hopper flash were programmed. When the initial fixed ratio was small, the sequence with the 2-s reinforcer was preferred. Preference switched to the sequence with the 8-s reinforcer when the initial fixed ratio increased. In Phase 2, the effects of a 3-s hopper flash were compared with those of a 0.25-s hopper flash. The results showed that preference for the sequence with the 8-s reinforcer increased with hopper-flash duration. Together, Phase 1 and Phase 2 results show that reinforcer magnitude and ratio size of the second fixed ratio can affect choice, but their relative effects depend on initial fixed-ratio size and reinforcer duration.