Effects of Reinforcement Context on Initial Link Responding in Concurrent Chain Reinforcement Schedules

Previous research shows that relative initial- and terminal-link temporal duration influences concurrent chain choice proportions. However, little research has examined whether reinforcement outside of either links influences concurrent chain choice proportions and/or response rates. We examined this by conducting an experiment in which 11 pigeons responded on concurrent chain schedules that alternated with either fixed interval (FI) or fixed time (FT) reinforcement schedules. FI and FT schedules provided reinforcement every 20, 60 or 180 s. Concurrent chain schedules provided reinforcement on average every 60 s. Concurrent chain schedules were never available at the same time as the FI or FT schedule. Most pigeons decreased choice proportions as the temporal duration of the FI or FT schedules increased, similar to the initial-link effect. Consistent with behavior contrast research, initial link response rates significantly increased as reinforcement rate decreased during the FI and FT schedules. This is the first study to show that reinforcement outside of a concurrent chain schedule can significantly change choice proportions. The initial link response rate result suggests a novel way to look at initial link response rates, outside of changing reinforcement rates and temporal duration.