The Theory of Defensive Mimicry: what it is and what it says about emotions

Facial expressions such as laughing, crying and smiling could have a common origin.

Long before the appearance of language in the human species, non-verbal communication already existed. Thanks to gestures we are able to communicate: we smile, we cry, we shrug our shoulders, we raise our eyebrows... These behaviors are common and innate, but they are also symbolic, that is, they represent and communicate feelings and thoughts.

Although some of them, if you think about it carefully, are quite strange: Why do we show our teeth to express kindness? Why do salty water escape from our eyes to ask others for comfort? Why do we laugh to convey that something is funny to us?

In the field of anthropology it is widely recognized the importance of the face in interaction and social intelligence. We ourselves are able to infer feelings and communicate thanks to facial expressions.

Although we currently know the adaptive functions of other types of human behavior, such as emotions; they are our way of reacting to pain or psychological pleasure. The adaptive function of human facial expressions remains partly unknown.

Several current hypotheses have attempted to define the evolutionary roots of smiling, laughing, and crying. Recently, The theory of defensive mimicry has been proposed for its explanation., which proposes defensive reflexes as the common origin of the three behaviors. In this article we will explain in detail this recent evolutionary theory and the evolution of smiling, laughing and crying from it.

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What does the Theory of Defensive Mimicry say?

We have all cried with laughter, or have started to laugh in the middle of our own drama. Some ancient Greek philosophers and poets already realized the similarity between laughter and crying, especially as the degree and intensity of emotional expression increased. But... Why do laughter, smiles and tears look so much alike? Perhaps this similarity could not indicate the same root.

Defensive imitation theory proposes that some human emotional expressions originally evolved as exaggerated and prolonged imitations of our own defensive reflexes.

When we are faced with situations that are potentially life-threatening or physical, our body responds immediately and automatically by shortening our muscles. For example, in the startle reflex, muscle groups involving the neck and back contract.

These defensive reflexes produce a change in posture or body expression, and, therefore, convey information about the person's internal state. This information can be exploited by certain threatening animals. But, suppression of reflexes is not an option, since reflexes are necessary for survival, for example, contracting the muscles of the legs makes it easier to escape.

However, this knowledge of the internal state and apparent helplessness can be beneficial to the animal itself. If animals are aware that others can interpret their reactions, they can consciously imitate them.

For example, an animal can simulate a fear reflex, with its characteristic muscular expression, to manipulate the behavior of those around it. The surrounding animal may interpret fear as a sign of vulnerability and attack. Actually, this behavior was what the former was looking for, reversing the roles of victim and executioner. So, by performing imitated defensive actions, the animals could have learned to manipulate the behavior of others.

As proposed by the theory of defensive mimicry, these defensive reflexes could be in the origin of the social and symbolic expressions that we know as smiling, laughing and crying. This can adequately explain the physical formation of a wide range of emotional expressions, but not all.

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Study of defensive reflexes

A group of researchers realized that many human emotional expressions were also remarkably similar to another domain of behavior; reflective behaviors in primates. For several years they studied a set of reflexes responsible for protecting different parts of the body, especially focused on the startle reflex, in addition to other blocking reflexes and withdrawal.

These reflexes and their actions usually last less than a second, but can be studied thanks to video recording and the measurement of muscle activity involved. Examining them in detail, they found that they resembled the set of muscular actions involved in smiling, laughing, and crying.

At that time they established the premise of whether these reflexes or defensive actions could have been in the origin of the emotional expressions of humans, sowing the germ of the theory of mimicry or imitation defensive.

The first scientist to systematically study the human startle reaction was Lévi-Strauss, in the early 20th century, with the help of a movie camera. For his study, he used a rather unethical procedure; he fired a pistol behind the heads of psychiatric patients he had not informed.

He observed, across the recordings, a consistent set of movements within the first few hundredths of a second; each component was apparently useful to protect a part of the body. As far as the torso is concerned, the contraction of the muscles of the eyelids and faces to protect the eyes, the inclination of the the head down and forward to hide the teeth and face, the contraction of the shoulders to protect and the neck. Finally, the curvature of the torso causes the body to shorten, making it smaller, and therefore more difficult to reach. These "protective" movements occurred in different areas of the body.

Later studies showed that the degree of the reflex response varies greatly depending on the situation and the person. Someone who is very calm may have a very reduced response that involves only a slight tightening of the muscles around the eyes. A person in a state of stress or anticipatory anxiety will respond more extensively, using more muscle groups. As the degree of reflection increases, it spreads from the eyes (where it is strongest) to other parts of the face, and eventually to other parts of the body.

There are two main types of reflexes that serve to defend the different areas of the body, these work together and represent the initial and involuntary response that protects the organism.

After the initial reflex, there is a set of reflexive reactions, slower and more complex. This second phase involves a series of neurons called peripersonal. These neurons already take into account the place from where the threatening stimulus originates, if it comes from the left, the corresponding eyelid will close faster.

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Evolution of emotional expressions

Opinions differ on how signals evolve in animals. Information-based theories posit that signals evolve to transfer information from one animal to another about the environment. Non-information-based theories explain that cues evolve because they have a direct effect on the behavior of others.

Evolution of the smile

Regarding the evolution of the smile, it is striking how showing teeth, an obvious sign of threat, has managed to become a sign of non-aggression. However, it appears that tooth display as a threat and as a signal of non-aggression are fundamentally different and do not involve the same muscles. Being the non-aggression (the smile) related to defensive actions, to protect the eyes.
In this case, no attempt is made to define whether the human smile is a defensive action in itself or an evolution of it. It is suggested that the smile appeared rather as an exaggerated imitation of the same defensive action. The animals understood that thanks to that grimace, they could influence the behavior of others and avoid aggression. More than an evolution, it would be a conscious appropriation.

If we think about it, in the present we often use this “protective” smile. For example, when we make a driving mistake that involves another person, we often smile in a forced way, as an apology and to avoid anger.

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evolution of laughter

Could laughter be explained by an evolutionary process similar to that of smiling, mimicking defensive reflexes? Laughter appears to be a strong, exaggerated, extended imitation of a defensive reaction. Even the tears, which it sometimes produces, would be a reflexive response to protect the eyes, according to the defensive mimicry hypothesis.

The debate about which animals are capable of laughing is still open, this characteristic was believed to be exclusive to some apes and humans. A recent study concluded that smiling is widespread among animals; cows, dogs, foxes and some birds, such as magpies, exhibit this behavior, in addition to primates. Ethologists have described a gesture, common among many mammals, called the open-mouthed play face.

Laughter could, then, have evolved from the game. Let's say two animals play fight. A blow near the nose, with its consequent tears, would be a signal that a limit is being crossed and would end the game. Laughter also modulates the response, if it is soft, the game continues, if it intensifies the game comes to an end. An example would be laughter caused by tickling.

But, we humans laugh in different contexts, outside of pretend fights and tickles. Although it seems that laughter would fulfill the same function, it would be a reinforcement of a behavior. In the case of comedy, laughter serves as reinforcement to modulate the behavior of the comedian.

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evolution of crying

Crying, unlike laughter, is apparently unique to humans, making comparative studies with other animals difficult. Animals make sounds to ask for help. Human crying would be a signal to seek comfort from others.

For the evolutionary explanation of crying, based on defensive reflexes, it would be necessary to forget about tears at first; crying is not only the liquid that comes out of our eyes. Crying is accompanied by a series of muscular movements that are highly reminiscent of the defensive action that seeks to protect the eyes, already described by Strauss.

But why solicit consolation by mimicking the reflexes that normally trigger a heavy blow to the face? Behind the cases of consolation that occurred in primates there is an initial aggression or fight. Therefore, it is adaptive to have a mechanism to comfort the victim afterward and repair the friendship.

Crying would not be in itself an action of facial protection, but an imitation of the set of defensive actions who seek the same consolation that was offered, among apes, after the aggression.