Schofield, G., & Davison, M. (1997).
Nonstable concurrent choice in pigeons.
Journal of the Experimental Analysis of Behavior,
68, 219-232.
Six pigeons were trained on concurrent variable-interval
schedules in which the arranged reinforcer ratios changed from
session to session according to a 31-step pseudorandom binary
sequence. This procedure allows a quantitative analysis of the
degree to which performance in an experimental session is
affected by conditions in previous sessions. Two experiments were
carried out. In each, the size of the reinforcer ratios arranged
between the two concurrent schedules was varied between 31-step
conditions. In Experiment 1, the concurrent schedules were
arranged independently, and in Experiment 2 they were arranged
nonindependently. An extended form of the generalized matching
law described the relative contribution of past and present
events to present-session behavior. Total performance in sessions
was mostly determined by the reinforcer ratio in that session and
partially by reinforcers that had been obtained in previous
sessions. However, the initial exposure to the random sequence
produced a lower sensitivity to current-session reinforcers but
no difference in overall sensitivity to reinforcement. There was
no evidence that the size of the reinforcer ratios available on
the concurrent schedules affected either overall sensitivity to
reinforcement or the sensitivity to reinforcement in the current
session. There was also no evidence of any different performance
between independent and nonindependent scheduling. Because of
these invariances, this experiment validates the use of the
pseudorandom sequence for the fast determination of sensitivity
to reinforcement.
Key words: concurrent schedules, choice, acquisition, generalized
matching, keypeck, pigeons