Experiment 1 compared the responses of 10 laboratory-reared and 10 wild-reared rhesus monkeys iMacaca mulattai to a real snake and to a range of snake-like objects. Most wildreared monkeys showed considerable fear of the real. toy, and model snakes, whereas most lab-reared monkeys showed only very mild responses. Fear was indexed by unwillingness to approach food on the far side of the snake and by behavioral disturbance. Experiment 2 examined the effectiveness of seven flooding sessions in reducing snake fear in 8 wild-reared rhesus monkeys. Mean latency to reach for food, trials to criterion (four consecutive short latency responses), and total exposure time to criterion declined significantly across flooding sessions. Behavioral disturbance declined within sessions but not across sessions. Results of a final behavioral test revealed that substantial long-lasting changes had occurred in only 3 of the 8 monkeys. The results are discussed in the context of dissociation between different indices of fear.It has long been known that many adult primate species exhibit a marked fear of snakes. Some investigators who have studied this fear have suggested, or assumed, that it was "innate" or "spontaneous" (e.g., Hebb, 1946;Masserman & Pechtel, 1953; Morris & Morris, 1965). These terms are only meant to imply that the fear does not appear to result from any specific experience, although obviously maturational and/or general life experience factors may playa role in its development. Other investigators, by contrast, have argued that some form of learning or social tradition is likely to be involved in the origins of this fear. Yerkes and Yerkes (1936), for example, argued that their data supplied "no evidence of specific avoidance (fear) response prior to or apart from individual experience with a given type of object [e.g., snake]" (p, 64). They reached their conclusions largely because adult chimpanzees exhibited greater fear in their reaction to snakes than did infant chimpanzees (see also Haselrud, 1938). Schiller (1952) reached a similar conclusion regarding fear of snakes when he wrote "there is no evidence in the ape of innate specific responses to specific perceptual configurations [e.g., snakes]" (p, 182). His argument was based on results that showed differences in the rate of formation of approach and avoidance reactions to snakes and to other, more arbitrary, neutral objects. A somewhat more direct strategy for getting at the origins of snake fear than that used by Yerkes, Haselrud, or Schiller involves comparing the responses of lab-reared primates with those of wildreared primates. Although both Hebb (1946) and Yerkes and Yerkes (1936) had a mixture of wildand captive-reared chimpanzees in their studies, no systematic comparisons were made between the responses of the two groups. Furthermore, Yerkes and Yerkes noted that all their subjects had probably had experience with snakes even in their captive environment and that there was a good possibility that they had learned the fear. More recently, Joslin,...
