Fearful Behavior—Genetics and the Environment

Fear Dog 7.

Dog showing fearful behavior. Paw lifting indicates a beginning of pacifying behavior (photo by Mark Taylor).


Two important aspects of fear: (1) Fearful behavior has genetic and learned components, and (2) our pets may show fearful behavior because we have taught them that without being aware.

We usually distinguish between rational or appropriate, and irrational or inappropriate fears. The latter are called phobias, fears that are disproportional to the dangers in question, although some phobias do have a survival value.

Fear serves the survival of organisms by producing appropriate behavioral responses. Hence, it has been preserved and subject to adaptive changes throughout evolution according to the posed environmental challenges. From an evolutionary point of view, the particular fear behaviors of a species may be an adaptation that was useful at some point in the past. The distinctive responses to fear stimuli may have emerged and developed during different periods. For example, fear of heights, common to most mammals, has probably developed during the Mesozoic period; and fear of snakes, usual in simians, during the Cenozoic period. Claustrophobia, agoraphobia and aquaphobia may also have their origins in evolutionary adaptations.

Predator and prey have different strategies to deal with threats. Their behavioral strategies evolved throughout millennia under the constant struggle for survival. Predators avoid dangerous stimuli by creating distance, flight being the favored strategy. Prey animals freeze preferentially when the predator is still at a distance, but when that distance decreases to a critical value, the animal flees. Flight appears to be a genuine unconditional response to the unconditional stimulus that is a predator at a critical distance.

Fearful responses and their intensity seem to be a consequence of predisposing traits, resulting from many gene-environment interactions during the development of the individual. The latest research has clearly established a genetic basis for fear behavior. These studies were conducted with humans as well as other animals. In humans, researchers have been able to study the effect of genetics (family lines and twins) and environment (adoption cases).


Horses Running In The Wild.

Fleeing is the first strategy when facing a threat. Horses seldom gallop in nature except when fleeing from a predator.


Flight is the primary strategy that animals use in the face of a threat. This behavior is associated mainly with the sympathetic nervous system, which function is to mobilize the organism for the so-called fight-or-flight response originally described by Cannon. While flight is an active coping strategy when facing danger, freezing (immobilization) and hiding is a passive coping strategy. Depending on species, such a strategy is the next-best option to flight. Animals freeze and hide when escape is impossible. Freezing is characterized by an inhibitory activity in the autonomic system (hypotension, bradycardia), formerly described by Engel and Schmale as a conservation-withdrawal strategy.

Thanatosis, or tonic immobility, is an extreme form of freezing behavior. For example, white-tailed deer fawns (Odocoileus virginianus) can lower their heart rate to 38 beats per minute (from about 155) for up to two minutes.

Whether an animal shows a preference for an active or a passive defense strategy is not solely a question of the context. Research shows that some animals do have a preference for one strategy rather than the other. In exactly the same situation, two animals may respond differently. The interesting point is that these patterns, both behavioral and neuro-endocrinal seem to be consistent. Some researchers suggest that this may explain why some individuals are more resistant to stress and stress-induced malfunctions than others. Researchers found the tendency to react one way rather than the other to run in families, which suggests a genetic component. The experiments were conducted with rats and mice, but we have no reason to suspect that studies of other species would not show the same results.

Fear is probably experienced similarly in many species. All mammalian species show three different sites in the brain where electrical stimulation will produce a complete fear response: (1) the lateral and central regions of the amygdala, (2) the anterior and medial hypothalamus, and (3) areas of the PAG, the periaqueductal gray, which is the gray matter in the midbrain involved in the modulation of pain and defensive behavior. Researchers have also studied defensive strategies in various species and concluded that human reactions to threatening stimuli are not qualitatively different  from those of nonhuman mammals.


Dog Puppies Playing.

The early development has a critical influence on how animals will respond to challenges, stress and fear eliciting stimuli.


The amygdala seems particularly relevant. We suspect that it may have a significant function in regulating many facets of social behavior. It also appears that threatening stimuli activate the amygdala, which in turn has a decisive influence on the cognitive mechanisms of the individual, including perception of the environment, selective attention (relevant for learning), and memory.

Conclusion: Not surprisingly and in line with many other behavioral traits, it seems that fearful behavior depends upon two different factors: (1) a genetic predisposition, and (2) the influence of the environment. Environmental factors during the development of the young individual may be critical in its ability to cope with stress and fear eliciting stimuli. Early experiences appear to affect the neural and biochemical systems involved in fearful behavior and in coping with stress—as well as learning processes and the capacity to deal with threatening stimuli in adulthood. Maternal prenatal stress also seems to produce changes in the brain morphology of the fetus and consequently in its way of reacting to stress and fear eliciting stimuli later on.

While some fear responses are innate other are learned. Conditioned fear provides a critical survival-related function in the face of a threat by activating a range of protective (or defensive) behaviors. Therefore, we can presume that all animals will have a readiness to identify and retain the memory of any stimulus or situation they have perceived as potentially dangerous or threatening. This means that it is easy for animals to develop fearful behavior.

Watson demonstrated how fear can be a conditioned response with his famous (or infamous) experiments on Little Albert in 1920 who learned to fear a white rat. Some of the fear behavior of our pets, particularly dogs and cats, are created by us. An event that in itself might pass mostly unnoticed may be blown up to a disproportionate relevance if associated with a strong reaction of the owner. Dogs (and children) often face  situations with unexpected and somehow aversive results, which would soon be forgotten if it weren’t for the exaggerated reaction of the owners (parents). All living organisms are, in principle, prepared to deal with discomfort, aversive experiences and failure. The problem is when these assume proportions out of context because that are additionally reinforced. Many dogs fear strangers because their owners fear that the dogs fear strangers and their reactions reinforce the dogs’ disposition to be cautious about strangers. Often, and unaware of it, the owner is reinforcing the fear while attempting and believing that he/she is reassuring the dog. This is conditioned (learned) fear behavior.

We saw it clearly in the 1980s when we performed some experiments at the Ethology Institute. A litter of puppies from a suspected line of dogs prone to show fearful behavior exhibited entirely distinct behaviors one year after they were placed in six different homes. The dogs reflected, indeed in a significant degree, the attitude of their owners toward novelty and challenges. We repeated the experiment with another litter, this time from a confirmed non-fearful line, and the eight puppies showed the same tendency again when we tested them one year later. Even though there was a tendency for the dogs from the fearful line to be on average more cautious and the others to be bolder, they overlapped one another in the middle range of responses. Our tests did not include enough animals to enable us to draw a conclusive answer to the question of genetics versus environment in this aspect. However, they pointed out the importance of the environment, at least in what concerns the average domestic settings in which we can expect dogs to grow up.


Cannon, W. B. (1915). Bodily Changes in Pain, Hunger, Fear and Rage. New York, NY: Appleton.

Engel, G. L. and Schmale, A. H. (1972). Conservation withdrawal: a primary regulatory process for organic homeostasis. In: Physiology, Emotions and Psychosomatic Illness. New York, NY: Elsevier; 1972:57–95.

Kavaliers, M. and Choleris, E. (2001). Antipredator responses and defensive behavior: ecological and ethological approaches for the neurosciences. Neurosci Biobehav Rev. 2001;25:577–586.

Koolhaas, J. M. et al. (1999). Coping styles in animals: current status in behavior and stress-physiology. Neurosci Biobehav Rev. 1999;23:925–935.

McFarland D. (1987). The Oxford Companion to Animal Behaviour. Oxford, UK: Oxford University Press.

Panksepp, J. (1998). The sources of fear and anxiety in the brain. In: Panksepp J, ed. Affective Neuroscience.New York, NY: Oxford University Press; 1998:206–222.

Parmigiani, S., Palanza, P., Rodgers J. and Ferrari, P. F. (1999). Selection, evolution of behavior and animal models in behavioral neuroscience. Neurosci Biobehav Rev. 1999;23:957–970.

Perrez, M. and Reichert, M. (1992). Stress, Coping, and Health. Seattle, Wash: Hogrefe & Huber Publishers.

Steimer, T. (2002). The biology of fear- and anxiety-related behaviors. Dialogues Clin Neurosci. Sep 2002; 4(3): 231–249.

Watson, J. B. (1970). Behaviorism. 7th ed. New York, NY: WW Norton & Company.

Weinstock, M. (2001). Alterations induced by gestational stress in brain morphology and behaviour of the offspring. Prog Neurobiol. 2001;65:427–451.


"Ethology" by Roger Abrantes

If animal behavior fascinates you, you will enjoy "Ethology—The Study of Animal Behavior in the Natural Environment," the book and course by ethologist Roger Abrantes.
Enrolling for this course puts you in direct contact with the author to whom you can pose any question while you complete your coursework. Click here to read more and enroll.

Fearful Behavior—the Making of a Definition

Fear Coyote.

Fear is a protection mechanism honed throughout evolution. Taking evading action is the first priority for the fearful animal (photo by Max Waugh).


We have discussed aggressive behavior (1 and 2). Now, we will examine fearful behavior beginning (as always) with a definition. Let us look at existing definitions.

Fear is an unpleasant often strong emotion caused by anticipation or awareness of danger (Merriam-Webster).” As a dictionary definition (and that’s what it is) it works, but we need to be more precise.

Fear is the unpleasant emotional state consisting of psychological and psychophysiological responses to a real external threat or danger.” (Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition). This definition is more precise. However, to evaluate it properly, we need first a definition of threat, particularly the explanation of what real external threats are versus what the text leaves us presuming are not real threats. The term unpleasant is vague. How can we observe psychological responses? We cannot. What we can observe are the behavioral changes, but that is not what the definition says. We can measure some psychophysiological responses, but I wouldn’t rely entirely and solely on them to analyze the consequence of a fearful experience.


When facing a threat, and flight is not possible, the next best option is to hide and freeze (photo from Molly’ s Just You Only Better).

“Fear is a normal emotional response to consciously recognized external sources of danger such as those often associated with loud noises, threatening gestures, strange people and thunderstorms; it is manifested in animals by flight, by attack or by cringing.” (Saunders Comprehensive Veterinary Dictionary, 3 ed.). This definition contains the explanation of real threats (consciously recognized external sources of danger) that we missed above. It also gives us examples. Whether fear is manifested by flight, by attack or by cringing is controversial for an ethologist because these all have different functions. They appear together is this definition, probably because veterinarian science tends to classify behavior by symptoms (as is the practice in its field) and not function as evolutionary biologists (and ethologists) do. Flight is triggered by a fearful stimulus (function=eliminate a threat), but attack is aggressive behavior, even when defensive (function=eliminate competition), and cringing (a term not commonly used in the behavioral sciences) may signify submissive behavior, which is not the same as fearful behavior (function=eliminate a social threat).

“Fear is an emotion induced by a threat perceived by living entities, which causes a change in brain and organ function and ultimately a change in behavior, such as running away, hiding or freezing from traumatic events.” (Wikipedia). This is a good definition. It relates emotion with behavior, which is always sweet music to the ears of the ethologist who prefers to deal with observable and measurable phenomena rather than the occult emotions. Running away, hiding or freezing are compatible as to function, so we have no problem with that. Traumatic events, on the other hand, requires an explanation.

Emotions are experienced and expressed at three different levels: (1) the psychological level, (2) the neurophysiological level, and (3) the behavioral level. All three aspects are present in all emotions. While psychologists focus on the first level and psychiatrists on the second, ethologists focus on the third.

“The main function of fear and anxiety is to act as a signal of danger, threat, or motivational conflict, and to trigger appropriate adaptive responses. For some authors, fear and anxiety are indistinguishable, whereas others believe that they are distinct phenomena.” (Steimer). This is a short, precise and strong definition. It gives us the function of fear and points out an important distinction to a related term, anxiety, which “[…] is a generalized response to an unknown threat or internal conflict, whereas fear is focused on known external danger.”

Steimer’s and my definition are fully compatible. Here is my definition:

Fearful behavior is behavior directed toward the elimination of an incoming threat, e.g. fleeing, freezing or hiding. Submissive behavior is behavior directed toward the elimination of a social-threat from a mate, i.e. losing temporary access to a resource without incurring injury, e.g., and highly depending on species, lying down on the back, assuming a low-profile body posture, or turning the neck away.”

My definition is identical to Steimer’s, only focusing on the behavior and compiling all triggering factors under one label, threats. Moreover, I prefer to pinpoint the distinction to the related submissive behavior (instead of anxiety). Mine is a more extreme ethological definition and has the advantage of adding an explanation of submissive behavior. Steiner’s has the advantage of relating to anxiety and is more likely to be adopted by human psychologists and psychiatrists.

Both Steimer’s and my definition require a definition of threat. Steimer does not explicitly give us one. I do, and one, which is compatible with both definitions.

“A threat is everything that may harm, inflict pain or injury, or decrease an individual’s chance of survival. A social-threat is everything that may result in the temporary loss of a resource and may cause submissive behavior or flight, without the submissive individual incurring injury.”


When facing a social-threat, submissive behavior is the best option. This dog shows what ethologists call active-submissive behavior (photo from safekidssafedogs).

I’m compelled (Steimer is not) to distinguish between threat and social-threat because, in my definition, I pinpointed the difference between fearful and submissive behavior.

I have used a term that also needs a definition, namely, mate.

“Mates are two or more animals that live close together and depend on one another for survival. Aliens are two or more animals that do not live close together and do not depend on one another for survival.”

McFarland explains fear as a motivational state triggered by particular stimuli that give rise to defensive behavior or escape. Fear is one the primary motivators because of it’s life-saving function. Newborn and infants show innate fear responses to particular stimuli that may harm them. Environmental disturbances require habituation. Their fear of novelty loses its strength gradually and only comes back much later when trying new ways amounts to the spending of more energy (heavily penalized in nature) than doing it as they always have done.

Fear sometimes occurs  in conjunction with other motivators. Approach-escape conflicts are typical examples and result often in displacement behavior as, for example, self-grooming. We may argue that displacement behavior indicates the kind of fear that psychologists call anxiety. However, ethology does not need to introduce a new term because its definition of fear includes the biological aspects of anxiety.

Even if anxiety and fear are probably distinct emotional states, there may be some common aspects in their brain and behavioral mechanisms. As Barlow says, anxiety may just be a more elaborate form of fear enabling the individual with an increased capacity to adapt and plan for the future. In Steimer’s words, “If this is the case, we can expect that part of the fear-mediating mechanisms elaborated during evolution to protect the individual from an immediate danger have been somehow ‘recycled’ to develop the sophisticated systems required to protect us from more distant or virtual threats.”

When describing animal behavior it is more useful to refer to fear and fearful behavior than anxiety. We must also bear in mind that fearful is an adjective of behavior. To label a particular animal as fearful might be to go over the top. An animal may show fearful behavior, and rightly so, in certain situations and not in others.

Fear and fearful behavior evolved with the vital function of protecting the individual and are, therefore, mechanisms, which we may presume have a strong genetic correlation. Animals of different species show fearful behavior to different stimuli and in different degrees. It is natural and normal behavior for almost all animals (if not all) to get startled by a loud noise or a sudden movement. Horses and Guinea pigs get easier startled by more and different stimuli than dogs because they are prey animals, but they come over it quickly. They are not more fearful animals per se—they are just different, and a comparison at this plan is meaningless.

Two important aspects of fear: (1) Fearful behavior has genetic and learned components, and (2) not seldom, our pets show fearful behavior because we have taught them that without being aware. These are the topics for next time. Watch this space (as they say).


Barlow, D. H. (2000).Unraveling the mysteries of anxiety and its disorders from the perspective of emotion theory. Am Psychol. 55:1247–1263.

LeDoux, J. (1998). The Emotional Brain. New York, NY: Simon & Schuster.

McFarland D. (1987). The Oxford Companion to Animal Behaviour. Oxford, UK: Oxford University Press.

Steimer, T. (2002). The biology of fear- and anxiety-related behaviors. Dialogues Clin Neurosci. Sep 2002; 4(3): 231–249.

Strongman, K. T. (1996). The Psychology of Emotion. Theories of Emotion in Perspective. Chichester, UK: John Wiley & sons.

Watson,  J. B. (1970). Behaviorism. 7th ed. New York, NY: WW Norton & Company.


"Ethology" by Roger Abrantes

If animal behavior fascinates you, you will enjoy "Ethology—The Study of Animal Behavior in the Natural Environment," the book and course by ethologist Roger Abrantes.
Enrolling for this course puts you in direct contact with the author to whom you can pose any question while you complete your coursework. Click here to read more and enroll.