McIlvane, W. J., Kledaras, J. B., Callahan, T. C., & Dube, W. V. (2002).
High-probability stimulus control topographies with delayed S+ onset in a simultaneous discrimination procedure.
Journal of the Experimental Analysis of Behavior,
77, 189-198.
Experimenters and teachers use discrimination learning procedures
to encourage reliable attending to stimulus differences defined
as relevant for their purposes. Put another way, the goal of
discrimination training is to establish high-probability
stimulus control topographies that are coherent with experimenter
or teacher specifications. The present research was conducted to
investigate a novel procedure for encouraging stimulus control
topography coherence. Participants were 13 adolescents with
severe intellectual handicaps. During an initial Condition A, all
were exposed to a simultaneous discrimination procedure.
Participants could select a form alternating with a black field
(S+) or an identical form that did not alternate (S-). Accuracy
scores were typically low, and there was little evidence of
coherent stimulus control topographies. Subsequently, the
procedure was changed. During Condition B, every trial initially
presented two identical nonalternating S- forms (Trial State 1).
If the participant made no selection for 5 s, one of the forms
began to alternate with the black field, and he or she could make
the S+/S- discrimination (Trial State 2). Selections during Trial
State 1 prolonged the delay to Trial State 2 until there had been
no response for 5 s. During Condition B, S+/S- discrimination
accuracy scores improved rapidly and markedly for most
participants. Reinstating Condition A often resulted in
diminished accuracy scores. This study thus (a) demonstrated a
novel procedure for encouraging stimulus control topography
coherence and (b) provided support for the interpretation that
intermediate accuracy scores may be due to different topographies
of stimulus control that co-occur in the same discriminative
baseline.
Key words: discrimination learning, stimulus control
topographies, key press, humans with mental retardation