Kyonka, E. G. E. & Grace, R.C. (2008).
Rapid acquisition of preference in concurrent chains when alternatives
differ on multiple dimensions of reinforcement.
Journal of the Experimental Analysis of Behavior, 89, 49-69.
Pigeons responded in a concurrent-chains procedure in which terminal-link reinforcer variables were
changed unpredictably across sessions. In Experiment 1, the terminal-link schedules were fixed-interval
(FI) 8 s and FI 16 s, and the reinforcer magnitudes were 2 s and 4 s. In Experiment 2 the probability of
reinforcement (100% or 50%) was varied with immediacy and magnitude. Multiple-regression analyses
showed that pigeonsŐ initial-link response allocation was determined by current-session reinforcer
variables, similar to previous studies which have varied only immediacy (Grace, Bragason, & McLean,
2003). Sensitivity coefficients were positive and statistically significant for all reinforcer variables in both
experiments. Analyses of responding within individual sessions showed that final levels of preference for
dominated sessions, in which all reinforcer variables favored the same terminal link, were more extreme
than for tradeoff sessions in which at least one reinforcer variable favored each alternative. This result
implies that response allocation was determined by multiple reinforcer variables within individual
sessions, consistent with the concatenated matching law. However, in Experiment 2, there was
a nonlinear (sigmoidal) relationship between response allocation and relative value, which suggests the
possibility that reinforcer variables may interact during acquisition, contrary to the matching law.
Key words: acquisition, concurrent chains, reinforcer immediacy, reinforcer magnitude, reinforcer
probability, key peck, pigeons