Grace, R. C., & Savastano, H. I. (1997).
Transfer tests of stimulus value in concurrent chains.
Journal of the Experimental Analysis of Behavior,
68, 93-115.
We report two exper iments that use transfer tests to investigate
whether in concurrent chains the value of a terminal-link
stimulus is affected by the alternate terminal link. In
Experiment 1, two groups of pigeons were trained on multiple
concurrent-chains schedules in which switching between the
schedules was via pecking a changeover key. For one group, the
terminal links were fixed-interval 8 s versus fixed-interval 16 s
in one component and fixed-interval 16 s versus fixed-interval 32
s in the other component. For a second group, the terminal links
were variable-interval 10 s versus variable-interval 20 s in one
component and variable-interval 20 s versus variable-interval 40
s in the other. After sufficient baseline training had been given
so that performances had stabilized, transfer tests were
conducted in which the two chains with equal terminal-link
schedules were presented together as a new concurrent pair. For 6
of the 7 subjects, initial-link responding changed fairly rapidly
during the test in the manner predicted if the values of the
terminal links were equal. In Experiment 2, pigeons were trained
on multiple concurrent chains using a two-key procedure, and the
terminal links were the same variable-interval schedules as in
Experiment 1. After baseline training, transfer tests were
conducted that assessed (a) the relative reinforcing strength of
the terminal-link stimuli in a novel initial-link situation and
(b) the relative ability of those stimuli to evoke responding.
The data from the reinforcing strength test were consistent with
those from Experiment 1, but those from the evocation strength
test were not. Although this discrepancy shows that responding in
transfer tests is not solely a function of stimulus value, the
results from both experiments suggest, overall, that value is
determined by the stimulus—reinforcer relation independently
of the alternative terminal link.
Key words: choice, stimulus value, transfer test, context of
reinforcement, concurrent chains, key peck, pigeons