Adamson, Robert E.

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 observation of contrast effects (CE) in response
to differential relnforcenent has subsequently elicited a
diversity of experimental results and theoretical interpretations. Adaptation Level (AL ) concepts have provided
a mechanism for integrating such data within a psychophysical
frame-of-reference approach. The application of
this approach to the somewhat neglected area of response-produced
stimuli associated with effort, suggests that
proprioceptive stimuli may be effectively evaluated in a
simllar manner. Following shifts in the amount of effort
required to produce a constant reward magnitude, performance
measures demonstrated positive and negative contrast
effects (PCE; NCE) in relation to an appropriate control
performance. Data analysis suggested that the combined
effects of greater effort and shift conditions tended to
increase resistance to extinction. The findings are not
consistent Kith traditional (e. g., Hull, Spence) concepts
with regard to CE and the influence of effort on performance. It is suggested that such effects are more consistent with a contextual, or frame-of- reference, viewpoint.

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.

Two groups of rats received training and testing in learning
situations designed to induce perseveration. One task involved discrimination
training on one bar of a two-bar Skinner box and a
subsequent shift of reinforcement to the opposite bar. The second
task was a maze-learning one in which the training route was blocked
after 40 trials at a point just before the entrance to the goal box.
Thereafter, access to the goal box was possible only through a shorter,
but not previously reinforced route. The third task involved escape
training through one door of a four-door shock compartment. After 40
trials, the training door was locked and S was permitted to escape
shock only through one of the three previously-locked doors. In each
of the three tasks, indices of initial learning and perseveration were
selected, and within-subject comparisons were made for both initial
learning and perseveration across tasks. Within each task there was
a comparison of the initial learning measures to those used to define
perseveration. Finally, one of the groups was given conditioning and
extinction sessions in a single-bar Skinner box. The extinction
measure was compared with perseveration measures in the other tasks.
Four hypotheses were stated. These were that between tasks perseverative
measures would be positively related; that between tasks
initial learning measures would be positively related; that within each
task initial learning and perseveration would be neeatively related;
and finally that extinction in the single-bar Skinner box would have a positive relationship to measures of perseveration in the other tasks.
Only the last two hypotheses were supported and this support was not
uncontradicted. Also~ in the case of the extinction-perseveration
comparisons, none of the supporting evidence reached significance at
the .05 level of confidence.

Twenty-eight male hooded rats were trained with a time correlated cue called al1 clock. The Ss were divided into four matched groups for the four experimental procedures. The light out group had the time correlated cue removed.
Two groups received 50% reinforcement; one on an alternating schedule, the other on a random basis. The regular group continued training with the clock.
It was predicted that animals under the greatest control of the clock would exhibit the best temporal discrimination. Dew’s notion that schedules and external stimulation provide more control than the immediate effects of reinforcement over behavior was tested. Helson’s adaptation level theory predicted that the two 50% groups would perform similarly.
All four groups were significantly different from each other (p .001) based on the percent correct responses. Animals under the greatest control of the clock had the best temporal discriminations. Dew’s notion was supported. Helson's theory could not account for the differences between the two 50% reinforcement groups.

An attempt was made to investigate the intradimensional
transfer of a simultaneously presented, double brightness discrimination
in male hooded rats. It was hypothesized that in
a paradigm designed to emphasize interstimulus cues over
individual stimulus cues, subjects would exhibit transposition
in testing, even when this involved approaching a previously
negative stimulus, and avoiding a previously positive stimulus,
under extinction conditions. Results of two tests (with a partial reinforcement retraining
session between them) indicated significant transposition
on all measures except trial of first choice on Test I
for the group trained to approach the brighter stimulus in any
pair presented. Results were interpreted as being in support
of relational theory which stresses the importance of dimensional
salience in the establishment of relational responding.