Extinction (Psychology)

Ten male albino rats were trained In a brightness discrimination
problem where they were reQuired to choose a sttmulus value of
0.053 ft/cd over one of 0.012 ft/cd. Pairs were matched accordlng to
the number of trials requtred to reach a criterion of 18/20 correct
responses then randomly assigned to one of two grouos for testing In
transposition. Both groups were tested on the orlgtnally positive stimulus and a brighter one: 1.25 ft/cd for Group 8-C and 5.38 ft/cd
for Group 8-D. By testing for transposttlon wtth non-reinforced trials, contrary to the usual method, a tendency toward converging measures
of transposltton was achteved. Transposition for Group 8-D, In the
situation most dissimilar to training, was greater than for 8-C.
These results were discussed from relational or Gestalt, Spence model,
and Adaptation Level positions and It was shown that the results are
contrary to traditional Gestalt predictions. It was oredlcted that, according to underlying assumptions of
the Spence model, with continued non-reinforced trials, per cent of
transposition for both groups would decrease until a chance level of
responding was reached. That this did not occur cannot be explained
by the Spence model. Because the variability was too great with such a small N,
these results did not reach the .05 level of probability.

The purpose of this study was to determine the extent to which preadaptation to differential brightness magnitude affects responses to a constant postadaptation stimulus. Twenty-four male albino rats, one hundred and tweny days old, were divided into four groups and differentially preadapted in Skinner-boxes to 236.90, 77.25, 22.87, and 1.27 apparent foot-candles for 10 minutes, without access to a bar. Immediately following this period the Ss were allowed to respond under continuous reinforcement to a postadaptation stimulus of 236.90 apparent foot-candles. Measurement in terms of bar pressing indicated that the four groups extinguished differentially over six days. The control group, for whom the discrepancy bwtween preadaptation magnitude and postadaptation stimulus remained zero, was found most resistant to extiction during this period. Additionally, increases in the discrepancy between the pre- and postadaptation magnitudes led to experimental groups. The implications of these data for the proposition of stimulus definitions in terms of behaviorally effective magnitudes were discussed.

Following 20 shock-escape training trials, two experimental groups of
rats were reinforced for either running quickly (DRH animals could
preclude shock in the center section of the runway by decreasing their
starting latencies) or for running slowly (DRL animals could preclude
shock in the center section of the runway by increasing their starting
latencies). Results showed that the DRH animals were running consistently
faster than the DRL animals. The results were discussed in
terms of the existing explanations of vicious circle behavior, as well
as in terms of the differential effects of the reinforcement contingencies.

The resistance to extinction effect produced by non-response
contingent shock and light was studied using rats
as Ss. Three hypotheses which could account for resistance
to extinction were tested by varying the conditions of shock
or light in acquisition and extinction. Light showed a
tendency to disinhibit responding when responding decreased
in extinction. No elicitation or discrimination effects
were found.

Twenty-four rats were trained to avoid shock in a shuttlebox,
receiving feedback for a correct response. During extinction,
matched pairs were tested under response contingent or
response independent feedback, with either shock or no shock. The combination of response contingent feedback and no shock
led to the greatest resistance to extinction. No other significant
differences were found. The results were used to support
the discrimination hypothesis, and concurred with other studies
with regard to: (1) the functional similarity of feedback and
CS termination in the acquisition and maintenance of avoidance,
and (2) the importance of the interaction of the response contingency
with the avoidance contingency, in determining the
effects on avoidance responding.

In view of the subject's reinforcement history during
avoidance training in the traditional vicious circle paradigm,
the author maintained that the stimulus complex changes little
during punished extinction. It was therefore reasoned that
vicious circle running during punished extinction might be
precluded by the presence of a feedback stimulus (FS) that
had been encountered during training only on avoidance trials.
To test this hypothesis, the presence of an FS and CS were
manipulated in both training and extinction to produce a 3 x 3
factorial design. An analysis of running speed revealed
that all groups ran significantly slower on initial extinction
trials than on terminal acquisition trials, an outcome inconsistent
with the literature. In addition, training condition
was found to affect rate of extinction and rate of acquisition,
although not significantly. These trends suggest that the
effects of punished extinction may be attenuated through the
manipulation of discriminative cues.

Thirty-six rats were used to study the effects of
manipulating both the density and response contingency of
feedback during the extinction (OE) of discriminated shuttle-box
avoidance. Three operant groups had the opportunity to
receive response-produced feedback on either 100, 60, or
30 per cent of the extinction trials. Three yoked groups
received the' same number and pattern of feedback stimuli
as the operant groups, but independently of their own behavior.
Significant ordering was obtained between all operant and
all yoked groups, and between operant and yoked groups at
all three feedback percentage levels. An ordering trend was
obtained for the feedback percentage dimension, which was,
however, not significant. The results, however, clearly
supported the discrimination hypothesis and upheld the
importance of response produced stimulus change in the
maintenance of avoidance behavior.

Rats with bilateral, electrolytic, dorsal-hippocampal lesions
were compared with operated controls in a straight runway to assess
the effects of the lesion on the animals' reactions to food-incentive
shifts. Within each surgical group, half the animals received 40
preshift trials with low reward while the other half received the same
number of trials with high reward, following this all Ss were shifted
to the opposite reward magnitude and received 40 additional trials.
At this point, the Ss were shifted back to original reward magnitudes
for another 40 trials. Finally, all Ss underwent experimental
extinction. The data failed to support the hypothesis that dorsal
hippocampal rats "overreact" to incentive shifts. Lesion animals, as
compared to controls, were less sensitive to the reward shifts and
showed more resistance to extinction. The results suggest that the
lesion produces a deficit in the Ss ability to vary behavior specially
on tasks that require response decrements. However, the lesion-produced
hyperactivity introduced confounding aspects to this interpretation.

The aversiveness of time-out from maximal FR schedules
of water reinforcement was assessed using rats as Ss. In one
stimulus condition, S could produce or avoid TOs by lengthening
or shortening pauses - after-reinforcement (PARs). In a
second stimulus condition, Ss could similarly produce or
prevent periods of stimulus change (SC). Results indicated
that TO as S[triangle] or as bar retraction were equally aversive.
Ss consistently shortened PARs and maintained the FR reinforcement
contingencies, although no differential effects of
SC conditions were observed. It was concluded that TO is
aversive due to lack of reinforcement availability rather
than to any effects specifically linked with extinction or
cues associated with non-reinforced responding.

Eighteen rats were used to study two procedures for the
extinction of discriminated avoidance. One group (OE) was
placed on extinction defined by presenting shocks as programmed
but independently of the S's responses, while the other group
(CE) was placed on classical extinction defined by the removal
of all shocks. The two procedures were compared in terms of
rate of decline and terminal level of extinction performance.
In addition, the two groups were placed on a discrimination
reversal task in order to assess each procedure's effects on
a new learning problem. The CE group reached a lower level of
extinction performance in a fewer number of blocks than the
OE Ss. Furthermore, the CE Ss were inferior to the OE Ss in
terms of discrimination reversal performance as well.
An interpretation of the results in terms of the removal
and reinstatement of cues was offered although an alternative
explanation relating to a change in the motivational states
of the two groups during extinction was also presented. The
interpretation in terms of the presence or absence of cues
seemed to account for more of the present findings than the
traditional one advocating changes in motivational levels
resulting from the two divergent extinction operations.