Interpolation of a single fixed-ratio component in a baseline of fixed-ratio schedules

A study was conducted in which two birds (pigeons) were trained to respond on a fixed-ratio (FR) 100 baseline, and three birds were trained to respond on a FR 20 baseline. After stable baseline performance, a single FR 10 was interpolated into the FR 100 baselines while a single FR 200 (FR 250 for one bird) was interpolated into the FR 20 baselines. This was called the uncued condition. The same interpolations were replicated in another condition except that a different stimulus was experimentally associated with the interpolated ratio (cued condition). The results showed that the pause following the uncued interpolated ratio was generally the shortest in the session compared to the postreinforcement pauses for the remaining ratios. This effect occurred regardless of the relative size of the interpolated ratio, although it was absent when the interpolated ratio was cued. Moreover, pauses in those ratio components following the uncued interpolated ratio were slightly reduced, suggesting that the interpolation procedure also produced field effects. The results are discussed in terms of their theoretical relevance to variable-ratio schedule performance.