Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford


  • Michael DaliliEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_2988-1


Conditioned Fear Fear Learning Fear Reaction Conditioning Theory Fear Acquisition 
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Real or imagined objects or situations that elicit psychological, physiological, biomedical, and behavioral responses to protect an organism against perceived danger or threat.


In Isaac Marks’ 1987 book Fears, Phobias, and Rituals: Panic, Anxiety, and Their Disorders, he described fear as an emotion produced following the perception of present or impending danger that leads an organism to avoid threat, has obvious survival value, and is normal in appropriate situations (Marks 1987). Fear reactions exist in humans and across animal species to protect or defend against present or anticipated threats in the environment. Fear is characterized by a number of psychological and physiological reactions and biomedical changes, occurring simultaneously or sequentially. These include visible behavioral expressions, such as freezing or fleeing, and accompanying psychological and physiological changes, such as feelings of terror, crying, a pounding heart, nausea, and an urge to run and hide. Finally, biomedical changes associated with fear include the secretion of both adrenalin and noradrenalin at the peripheral nerve ending of the autonomic nervous system. Marks suggested that some aspects of what we fear and how we express it are biologically determined, while others are affected by our individual and group experiences. Examining the development and acquisition of fears has been the focus of extensive research, as researchers have struggled to explain individual differences regarding if, when, and how both evolutionarily relevant and nonrelevant fears are formed.

Conditioning Theory of Fear Acquisition

Fears are assumed to be acquired and the process of acquisition is a form of conditioning. Fear conditioning is similar to classic conditioning pioneered by Pavlov (1927), but pairs the conditioned stimulus with an intrinsically noxious or harmful unconditioned stimulus to elicit species-typical fear responses. Proposed by Eysenck and Rachman (1965), the conditioning theory of fear acquisition assumes that any stimulus can be transformed into a fear signal. This theory suggests that given similar frequency and intensity of exposure, all stimuli should have nearly an equal chance of being transformed into fear signals. It also states that the strength of the fear is determined by intensity of the experience in addition to the number of repetitions of the association between the painful or frightening experience and the stimuli. Finally, the theory suggests that the likelihood of fear developing is increased by factors such as exposure to high-intensity pain and/or fear experiences and by frequent repetition of the novel association between the stimulus and the pain or fear. One of the most famous studies of fear conditioning was conducted by Watson and Rayner (1920), who conditioned fear of a white laboratory rat in a young infant referred to as “Albert” by pairing the presentation of the rat with a loud and frightening noise. They also observed that Albert’s conditioned fear generalized to similar furry stimuli, such as a rabbit and furry dog, consistent with the conditioning theory’s claim that stimuli resembling the fear-evoking ones also acquire fearful properties. However, Rachman (1977) noted that researchers had mixed results when testing Watson and Rayner’s finding and presented several arguments against the conditioning theory of fear acquisition. These included the failure of people to acquire fears in fear-evoking situations, difficulties producing conditioned fear reactions in humans, and evidence against the premise that any two stimuli can be associated with each other with equal ease. Therefore, Rachman proposed a three-pathway model of fear acquisition.

The Three-Pathway Model

While Rachman (1977) acknowledged that direct conditioning remained an important fear-induction process, he proposed that at least two other pathways could be identified, distinguished by being indirect processes of acquisition, and integrated into a single model. The first is the vicarious acquisition of fears, where humans and animals can acquire fear of a stimulus (animal, object, or situation) by witnessing another individual’s fear of it. Based on observational learning, Rachman suggested that fears could be acquired directly or vicariously and that neutral stimuli would likely acquire fearful qualities if they were directly or vicariously associated with painful or frightening experiences. The ability to appropriately detect and respond to signs of fear and pain in a member from the same species likely conferred an important selective advantage during evolution. In addition to alerting the receiver about potential imminent danger, they also assign a threat value to the context or cue associated with the threat (Olsson and Phelps 2007). A recent review of cross species research on vicarious fear learning, also referred to as social fear learning, by Askew and Field (2008) supports the claim that this pathway plays an important role in the development of many fears. However, researchers also agree that vicarious learning is likely a form of conditioning and that experiencing an aversive episode vicariously may not in itself be sufficient to predict fear acquisition.

The second pathway proposed by Rachman was fear acquisition by the transmission of information and/or instruction. He remarked that information giving is an inherent part of raising a child, carried out continuously by parents and peers during the child’s earliest years, and is likely the basis for the most commonly encountered fears of everyday life. However, fears acquired in this way are more likely to be mild rather than severe. Rachman proposed that an advantage of these two additional pathways was that unlike conditioning, they could account for the fact that people display fears of situations and objects which they have never encountered. He suggested that accepting that fears can be acquired by informational processes allows us to explain some, but not all, of the failures to acquire fear in situations where it might have been expected to occur based on the conditioning theory. That is because information and instruction also help humans and animals to learn to distinguish those situations and objects which are not dangerous and therefore need not be feared.

The Nonassociative Pathway

Decades later, Poulton and Menzies (2002b) proposed a fourth pathway to account for fears that are not acquired by conditioning or other learning processes, for which the three-pathway model struggles to explain. They suggested that the addition of a nonassociative pathway contributes to the understanding of the nonrandom distribution of fears, failures to recall conditioning events in fear onset, and the seemingly paradoxical finding that people with high levels of fear report less direct traumatic events than those without such fear. Poulton and Menzies claim that a nonassociative model of fear acquisition asserts that members of a species, given normal maturational processes and background experiences, will show fear to a set of biologically and evolutionary-relevant stimuli. Evolutionary-relevant fears (e.g., fears of spiders, heights, water, darkness) acquired in this way would have the following features: the feared stimulus must represent a longstanding danger to the species, fear and avoidance of the stimulus must have increased reproductive opportunities in our ancestors, and the fear and avoidance of this stimulus is partly under genetic control. Therefore, this pathway enables researchers to account for fears with an evolutionary background appearing without any relevant direct or indirect associative learning experiences. Evidence for the nonassociative model has largely come from the findings of retrospective and longitudinal cohort studies, which suggest that relevant associative learning experiences had not occurred based on recall by phobic individuals. Critics of this model highlighted methodological problems with these studies, such as the unreliability of retrospective recall, especially when it is generally many years after the alleged experience took place (Mineka and Öhman 2002). However, Poulton and Menzies (2002a) maintained that an expanded four-pathway model offers the most inclusive, comprehensive, and parsimonious theoretical account of fear acquisition that integrates diverse findings from multiple disciplines.


Fears are crucial to the survival and well-being of humans and animals, allowing organisms to avoid threat, react to danger, and enhance performance. Fear is a package of reactions, occurring simultaneously or sequentially, resulting in psychological, physiological, biomedical, and behavioral changes. Theoretical models of how fears are acquired have changed, starting with a direct conditioning theory of fear acquisition, to a three-pathway model that includes indirect acquisition pathways, and finally to a four-pathway model to incorporate a nonassociative pathway of fear acquisition. This comprehensive model of how fears are acquired is crucial in order to understand the development and treatment of maladaptive fear such as anxiety and phobias.



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© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.University of BristolBristolUK