This paper reviews a program of research on the development of visual functions and social responsiveness in infant rhesus monkeys (Macuca mulutta). One study involved a clinical examination of simple visual reflexes (e.g., orienting) and more complex visuo-motor responses (e.g., gaze aversion and reaching). Such responses changed dramatically over the first two weeks of life. Two other studies used infrared corneal-reflection techniques to monitor visual scanning: One determined when infant monkeys became sensitive to the direction of a conspecific's gaze. By week three, rhesus monkeys scanned faces looking back at them less than faces looking away. The other study investigated whether, like human infants, young monkeys shift from scanning external contours of a pattern to scanning internal details. Unlike human infants, however, young monkeys shifted from proportionally more internal scanning to proportionally more external scanning. As a whole, the studies demonstrated rapid development of visual functions and visually cued social responses and raised important questions for future research.Key words: Macaca mulatta, rhesus monkey, visual reflexes, infants, development, gaze aversion, corneal-reflection technique
INTRODUCTIONPart of a research program on visual and social development in the infant rhesus monkey (Macaca mulatta) is described here. One study involved a clinical examination of simple visual and social functions in the first three weeks of life [Mendelson, 19821. Two other studies used infrared corneal-reflection techniques [Mendelson et al, 19811 to explore scanning of faces IMendelson et al, 1982aj and scanning of geometric forms [Mendelson et al, 1982b] during the first seven weeks of life. Although limited to a short age span, the studies uncovered dramatic changes in perceptual functions and social responses. An overview of the methods used and of the developmental changes observed is presented here.
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A Clinical Examination of Visual FunctionsBehavioral research on vision in infant monkeys has typically been limited to paradigms using motor responses and learning techniques [see Boothe & Sackett, 1975 for a review]. With the exception of the forced-choice preferential looking paradigm [e.g., Teller et al, 1978) and habituation paradigms [e.g., Swartz, 19821 that have only recently been used with monkeys, these methods are not useful for studying young infants. Consequently, there is very little information on visual functions in the young monkey. I t was necessary to collect normative data from a battery of tests which assessed simple reflexes, visuo-motor functions, and social responses in early infancy [Mendelson, 19821. Fifteen rhesus monkeys (eight males and seven females) served as subjects. They were received in the laboratory as early as their day of birth, but not later than five days of age. They were reared in a primate nursery according to standard procedures [Bowden et al, 19711. Although housed in individual cages, they had visual, auditory, and some physical ...
