For years theorists have hypothesized on the basis of meagre evidence that observational conditioning is involved in the origins of many human and nonhuman primates* fears and phobias The present experiments provide strong support for this hypothesis by demonstrating observational conditioning of snake fear in rhesus monkeys Experiment l demonstrated the usefulness of a new index of snake fear in rhesus monkeys and, using this new measure, also demonstrated that young monkeys raised by parents who have a fear of snakes do not acquire this fear in the absence of any specific experience with snakes In Experiment 2, however, five out of six adolescent/young-adult rhesus monkeys did acquire an intense and persistent fear of snakes as a result of observing their wild-reared parents behave fearfully in the presence of real, toy, and model snakes for a short period of time. The fear was not context specific and showed no significant signs of diminution at 3-month follow-up Implications of the present results for current theories of the origins of human fears and phobias are discussed.

Three experiments used an illusory correlation paradigm to assess the effects of fear on the perception of the covariation between fear-relevant stimuli and shock. In Experiment 1, high- and low-fear women were exposed to 72 trials during each of which a fear-relevant (snake or spider) or fear-irrelevant (mushroom and flower) slide was followed by a shock, a tone, or nothing. Although the relation between slide types and outcomes was random, high-fear subjects markedly overestimated the contingency between feared slides and shock. Experiment 2 showed that this bias was due to the aversive, rather than more generally salient, features of shock. Low-fear subjects demonstrated biases equivalent to those of high-fear subjects only when the base rate of shock was increased from 33% to 50% in Experiment 3. It is concluded that fear may be linked to biases that serve to confirm fear. The relevance of the present findings to preparedness theory is also discussed.

Two experiments examined whether superior observational conditioning of fear occurs in observer rhesus monkeys that watch model monkeys exhibit an intense fear of fear-relevant, as compared with fear-irrelevant, stimuli. In both experiments, videotapes of model monkeys behaving fearfully were spliced so that it appeared that the models were reacting fearfully either to fear-relevant stimuli (toy snakes or a toy crocodile), or to fear-irrelevant stimuli (flowers or a toy rabbit). Observer groups watched one of four kinds of videotapes for 12 sessions. Results indicated that observers acquired a fear of fear-relevant stimuli (toy snakes and toy crocodile), but not of fear-irrelevant stimuli (flowers and toy rabbit). Implications of the present results for the preparedness theory of phobias are discussed.

Three experiments support the hypothesis that mechanisms involved in observational conditioning (OC) of fear are similar to those of direct classical conditioning and involve the organism attempting to detect the causal structure of its environment. Experiment 1, a correlational analysis, shows that model monkeys' fear behaviors on snake trials (unconditioned stimulus [US]) were highly correlated with observer monkeys' fear (unconditioned response) while watching the models' fear. In Experiment 2, all observers showed distress while watching the model's fear during Session 1 of OC, but only observers who could see the snake to which the model was reacting continued to show fear during subsequent OC sessions, suggesting that the model's fear is an easily habituable US. In Experiment 3, observers acquired significant fear of snakes after 1 OC session, indicating that the continued fear of those Experiment 2 observers that could see the snake may reflect their own acquired fear of snakes.

Four experiments compared the level of fear conditioned with escapable versus inescapable shock. In Experiments 1 and 2, master subjects that had received 50 unsignaled escapable shocks were less afraid of the situation where the shock had occurred than were yoked subjects that had received inescapable shocks. Comparable results were found in Experiments 3 and 4, which used freezing as an index of fear of a discrete conditioned stimulus (CS) that had been paired with shock. Interestingly, control per se was not necessary to produce the low level of fear seen in the master subjects: Yoked groups receiving a feedback signal at the time the master made an escape response showed a low level of fear that was comparable to that of the masters and significantly less than that seen in the yoked.subjects without feedback. In addition, there were strong suggestions that control and feedback exert their effects through the same or highly similar mechanisms. Possible explanations for how control and the exteroceptive feedback signal produce this effect are discussed.