Fear of snakes in wild- and laboratory-reared rhesus monkeys (Macaca mulatta)

Abstract

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,...

Evolution, emotions, and emotional disorders.

“…Rabbits without an innate fear of foxes have an often-fatal anxiety disorder. However, even fear of snakes is not innate in primates but is only a cue especially conducive to fear conditioning (Mineka, Keir, & Price, 1980). Classical conditioning of emotions allows organisms to experience affect that slightly anticipates an event.…”

Socially learned habituation to human observers in wild chimpanzees

“…Observational conditioning or social referencing may also be particularly relevant for understanding habituation in the sense that they involve the ability to attribute another's behavioural response to an external event (Feinman et al 1992 Although examples of observational conditioning or social referencing in the wild are scarce, captive studies have revealed the relevance and importance of these mechanisms during the developmental stages of nonhuman primates. For example, in a classic study, Mineka et al ( 1984 ) demonstrated that naïve captive rhesus monkeys showed no initial fear of snakes, but quickly learned to fear them by observing the responses of their (wild-born) parents. In a follow-up study, it was demonstrated that these learned responses were acquired more easily for biologically relevant than irrelevant stimuli.…”

“…Various mechanisms have been discerned within social learning, including imitation, stimulus enhancement, observational conditioning, and emulation (Sherry and Galef 1984 ;; Mineka et al 1984 ;; Tomasello 1990 ;; reviewed by Whiten and Ham 1992 ). Research on social learning has a distinguished history, starting with early reports based on anecdotal observations of natural behaviour (e.g.…”

Comparison of the Effects of Bilateral Orbital Prefrontal Cortex Lesions and Amygdala Lesions on Emotional Responses in Rhesus Monkeys

“…The method was adapted from Mineka and her colleagues (Mineka et al, 1980;Mineka, 1987) and is identical to that reported previously . On each trial, the monkeys were allowed to reach for and to procure a food reward that had been placed on top of the clear box.…”