First Advisor

Cord Sengstake

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Psychology






Psychobiology, Mammals -- Behavior, Rhesus monkey -- Behavior, Protein deficiency



Physical Description

3, ix, 105 leaves: ill. 28 cm.


It has been well documented that protein calorie malnutrition (PCM) gives rise to physiological and behavioral deficits. These deficits include changes in emotional, exploratory and social behaviors of the malnourished organism. In particular, previous research has demonstrated that Feci from infancy results in avoidance of and failure to initiate social interactions as well as decreased contact with the environment, which in turn, further disrupt emotional and social development. This study examined the effects of chronic protein malnutrition on the social behavior of adult rhesus macaques by experimentally testing the hypothesis that deficient monkeys, unlike normal well-fed ones, are more likely to avoid social encounters than to seek them out. In addition, the animals' social interactions were recorded and analyzed. Subjects consisted of eleven adult rhesus monkeys (Macaca mulatta). Five were fed a protein-deficient diet (3.0 % of total kilocalories) and six were fed adequate amounts of protein (14 % of total kilocalories) from birth. After habituation to the test apparatus, subjects were trained to perform an operant response which opened a sliding door. During training, the response allowed access to food. In the final testing, opening the door allowed access to a social partner. If the subject performed the response and released a social partner, the social behaviors of the pair was recorded for ten minutes. Each subject was given three opportunities, on three separate occasions, to release every other subject. Protein-deficient subjects habituated to the experimental apparatus and acquired a simple operant response at the same rate as the control subjects. The protein-deficient monkeys, however, failed to generalize this operant response as rapidly as the control monkeys. As predicted, protein-deficient monkeys performed an operant response allowing access to a social partner less frequently than did the control monkeys. For like-diet pairings both the control and deficient subjects released approximately 60% of their partners; however, controls were far more likely to release a dissimilar diet partner (84% probability) than were deficient subjects (39% probability). Diet condition of the releasor was a significant factor, whereas diet condition of the release was not. Variables which could confound these findings were examined. It was found that: 1. The difference between diet groups was not accounted for by proximity of home cages; 2. Sex of the animals was not a confounding factor; 3. Although body weight and diet condition were highly correlated, body weight alone did not exert an effect above and beyond that of diet condition; 4. Dominance status, although correlated with both diet condition and body weight, showed only a weak correlation with the likelihood of one subject releasing another when the effect of diet condition was partialed out. In summary, diet condition played the major determining role in the frequency of release rates. Social behavior data was collected throughout the final phase of the experiment. Both groups of animals exhibited minimal play and sexual behaviors. Protein-deficient monkeys were more submissive than their matched controls. Subjects deviated most dramatically from one another in two behavioral clusters: disturbed (defined as self-stimulatory, autistic-like behaviors) and exploratory behaviors. Deficient monkeys engaged in more disturbed behaviors, while control monkeys engaged in more exploratory behaviors. Results are discussed in terms of behavioral similarity to social isolate animals, and possible nutritional-environmental interaction leading to chronic or persistent deficits in social development.


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Portland State University. Dept. of Psychology.

Persistent Identifier