Protein Preference in Protein-Malnourished Monkeys

10 protein-malnourished monkeys and 8 dietary controls were run in a preference experiment designed to look at the differences in the way the 2 groups accepted foods containing various amounts of protein. Each monkey was given choices among diets containing 2%, 3.5%, or 25% protein, and non-food objects. The protein-malnourished monkeys showed a marked preference for the high-protein food; the adequately nourished monkeys chose all foods at the same ratio. The results indicated that a rapid learning process was involved in the formation of a preference for high-protein foods. The colors of the 2% and the 25% diets were then reversed, and the protein-malnourished monkeys showed a temporary disruption in their preference behavior, but they soon established a stable preference for the high-protein food. The experimental results are consistent with the hypothesis that protein-malnourished rhesus monkeys have a specific hunger for protein.