Grace, R. C. (2004).
Temporal context in concurrent chains: I. Terminal-link duration.
Journal of Experimental Analysis of Behavior,
81, 215-237.
Two experiments are reported in which the ratio of the average times spent in the
terminal and initial links (Tt/Ti) in concurrent chains was varied. In
Experiment 1, pigeons responded in a three-component procedure in which
terminal-link variable-interval schedules were in constant ratio, but
their average duration increased across components by a factor of two.
The log initial-link response ratio was a negatively accelerated function of Tt/Ti.
Overall, the data were well described by Grace’s (1994) contextual choice model (CCM)
with temporal context represented as (Tt/Ti)k or 2Tt/(Tt + Ti), and by Mazur’s (2001)
hyperbolic value-added model (HVA), with each model accounting for approximately 93%
of the variance. In Experiment 2, fixed-parameter predictions for each model
were generated, based on the data from Experiment 1, for conditions in which
Tt/Ti was varied over a more extreme range. Data were consistent with the
predictions of CCM with temporal context represented as 2Tt/(Tt + Ti) and to
a lesser extent as (Tt/Ti)k, but not with HVA. Overall, these results suggest
that preference increases as a hyperbolic function of Tt/Ti when terminal-link
duration is increased relative to initial-link duration, with the terminal-link
schedule ratio held constant.
Key words: choice, concurrent chains, terminal-link duration,
reinforcement context, contextual choice model, hyperbolic value added model,
key peck, pigeons