Dube, W. V., & McIlvane, W. J. (1997).
Reinforcer frequency and restricted stimulus control.
Journal of the Experimental Analysis of Behavior,
68, 303-316.
Stimulus control was evaluated in 3 individuals with moderate to
severe mental retardation by delayed identity matching-to-sample
procedures that presented either one or two discrete forms as
sample stimuli on each trial. On pretests, accuracy scores on
one-sample trials were uniformly high. On two-sample trials, the
correct stimulus (i.e., the one that subsequently appeared in the
comparison array) varied unpredictably, and accuracy scores were
substantially lower, suggesting that both sample stimuli did not
exert stimulus control on every trial. Subjects were then given
training sessions with the one-sample task and with a new set of
four stimuli. For two of the stimuli, correct matching responses
were followed by reinforcers on a variable-ratio schedule that
led to a high reinforcer rate. For the other two stimuli, correct
responses were followed by reinforcers on a variable-ratio
schedule that led to a substantially lower reinforcer rate.
Results on two-sample tests that followed showed that (a) on
trials in which comparison arrays consisted of one high
reinforcer-rate and one low reinforcer-rate stimulus, subjects
most often selected the high-rate stimulus; and (b) on trials in
which the comparison arrays were either two high reinforcer-rate
stimuli or two low reinforcer-rate stimuli and the samples were
one high reinforcer- and one low reinforcer-rate stimulus,
accuracy was higher on trials with the high-rate comparisons.
These results indicate that the frequency of stimulus control by
high reinforcer-rate samples was greater than that by low
reinforcer-rate samples. Following more training with the
one-sample task and reversed reinforcement schedules for all
stimuli, the differences in stimulus control frequencies on
two-sample tests also reversed. These results demonstrate
experimental control by reinforcement contingencies of which of
two sample stimuli controlled selections in the two-sample task.
The procedures and results may prove to be relevant for
understanding restricted stimulus control and stimulus
overselectivity.
Key words: restricted stimulus control, stimulus overselectivity,
reinforcer rate, matching to sample, pointing, humans with mental
retardation