Date of Award

Winter 1995

Project Type


Program or Major


Degree Name

Doctor of Philosophy

First Advisor

John A Nevin


An extension of the generalized matching law is proposed as a model for choice in concurrent chains. The contextual choice model (CCM) assumes that effects of temporal context on choice are determined by the relative times spent in the terminal and initial links (Tt/Ti), and that terminal-link value is independent of temporal context. CCM gives an excellent description of a wide range of archival data, and because it simplifies to the generalized matching law when terminal-link duration is zero, provides a quantitative integration of concurrent chains and concurrent schedules. A series of experiments with pigeons as subjects is described to test and extend the model. Results indicate that: (a) reinforcement delay and magnitude are independent dimensions of value, as required by CCM; (b) when the definition of value is generalized to apply to delay distributions, CCM can also describe data on preference for variability in concurrent chains and the adjusting-delay procedure; (c) the function relating value to delay is the same in the two procedures; (d) terminal-link value is independent of temporal context, consistent with CCM but contrary to delay-reduction theory (DRT); (e) the relationship between DRT and CCM, as models for conditioned reinforcement, parallels that between contingency theory (Rescorla, 1968) and scalar expectancy theory (Gibbon & Balsam, 1981), as accounts of Pavlovian conditioning; (f) a ratio invariance in temporal context, i.e., effects of context on choice depend on the relative, not absolute, values of Tt and Ti, is approximately satisfied in concurrent chains; (g) preference is an increasing, negatively-accelerated function of Tt/Ti; and (h) when effects of bias, temporal context, and unequal terminal-link entries are accounted for by CCM, strict matching to relative terminal-link reinforcement immediacy may describe choice in concurrent chains. Therefore, when temporal context is characterized properly in the framework of the generalized matching law, concurrent chains may be viewed as a natural extension of concurrent schedules. Important goals for future research are the development of a molecular model that can explain temporal context effects and matching in concurrent chains, and whether temporal context effects are isomorphic in concurrent chains and in other procedures such as autoshaping.