Reward (Psychology)

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.

An attempt was made to determine the effects of
successive shifts in the quality of a reinforcing agent
upon the acquisition of a brightness discrimination. Two
levels of sucrose concentration (4 and 32%) were combined
factorially during preadaptation and discrimination phases.
Dependent measures included response rate and the number
of errors made during discrimination acquisition. Results indicated non-significant negative contrast
effects in errors and, in addition, negative contrast and
amount of reward effects in terms of response rate. It was
hypothesized that the absence of amount of reward effects
in errors and positive contrast in both dependent measures
was a function of a partial between groups design and
ceiling effects respectively.

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.