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Document Type

Article

Abstract

In a first series of experiments, 9 groups of rats were exposed
to 30 20-minute sessions of successive visual discrimination
training ("go/no-go," or mult FR-1 ext), where components (SD and
S!» were equal (1 min) in length. Responses during SD were
reinforced with a nonresetting delay (Experiment 1 a) or a resetting
delay (ORO, Experiment 1 b) of 1 s, 2 s, 3 S, or 5 s (a "no delay"
control group was also run). The terminal level and rate at which
stimulus control developed was inversely related to the obtained
delay, irrespective of cumulative reinforcers or reinforcement rate.
A second series of experiments explored the role of reinforcer
delivery as a discriminative stimulus, and the temporal regularity of
the component changes. In Experiment 2a, 4 groups of rats were
exposed to a mixed schedule where a delay factor (no delay and
5 s) was crossed with component type factor (fixed and variable
lengths), yielding a 2 x 2 design. A 5th group was exposed to a 2-
s delay with fixed components in Experiment 2b. Discriminative
responding was not observed for any of the delay groups, and only
a small effect of reinforcers was seen in the no-delay groups; no
effect of component type was found. The results from these
experiments demonstrate that delays to reinforcement retard the
acquisition of a visual discrimination and may decrease the degree
of stimulus control independent of the effects of delays on rate of
responding, rate of reinforcement, and reinforcer delivery, per se.
In addition, functions relating rate of responding in SD to rate of
reinforcement were differentiated on the basiis of the type of delay
contingency (non resetting vs. resetting) in contrast to an
apparently undifferentiated function relating rate of responding to
obtained delay.

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