Are Humans The Only Animals That Cry Tears

A sick baby cries long and plaintively in the night. A young adult female sobs in despair and disbelief at her husband'south death in the September eleven attacks. Nether cover of darkness, furtive tears neat in the eyes of a grown man watching the picture show Titanic. Every bit others grin and congratulate a bride, her mother weeps uncontrollably. Crying is at one time among the most familiar and the almost mysterious of human being behaviors. Certainly human facial anatomy and physiology are intricately engineered for both the discharge of tears and the facial and vocal expressions that accompany them—only for what purpose?

Tears have been around a very long time. All animals with mobile eyes have nictitating membranes, or inner eyelids, and tears that assistance in opening, endmost, washing, lubricating, and protecting the eye's frail, transparent, adaptive lenses. Simply humans, however, have evolved the tearing mechanism into a means of complex emotional expression, ane of the behaviors that make us unique among animals, even primates. Because every innate behavior is explainable in terms of adaptation for survival, we know that emotional crying must serve some important role in humans.

Observing that nosotros shed tears on our face—the part of our torso most visible and conspicuous to our social companions—some people accept theorized that crying evolved equally one of the many facial movements by which we communicate. Facial sensations, movements, and lacrimal secretions (tears) are all controlled by the same facial nervus. The human embryo's branchial arch, which becomes the lower office of the face, the neck, the lungs, and the heart, controls chewing, swallowing, animate, and vocalizing. Two of our nigh basic emotional expressions, laughing and crying, occur in this function of our trunk, utilise the same muscles, and are synchronized with stiff respiratory movements and vox. They do, however, involve strikingly different patterns of activity to achieve their unique forms of advice.

Crying may have evolved to telephone call attention to our distress by exaggerating the normal vehement that occurs when the facial nervus is activated. We can encounter this normal tearing when yawning or laughing also hard makes our optics h2o, or when irritation of our optics and the expanse effectually them stimulates tearing. Information technology seems likely that, in our afar by, vehement, together with vox, greatly increased the chances for survival of those infants who had acquired this capacity through random genetic mutation. As a result of the reward it conferred, the beliefs became lodged in our genome, and tears became a sign, and a symbol, of suffering.

As a mechanism of evolution, this kind of anatomical or physiological exaggeration is well known. The peacock's spectacular tail and the male caribou's gigantic antlers are both the work of a genetic positive feedback mechanism, increasing the size of the feature a little every generation because evolution favored the reproductive advantage that it conferred. Shedding tears could be a product of this same process.

Crying Rats, Weeping Elephants

Although circuitous emotional tears may be uniquely homo, most all baby birds and mammals have peculiar, high-pitched, repetitive calls for assist. This "separation cry" for their flagman has obvious survival advantages, not only eliciting rescue, assistance, and feeding, but besides signaling location. High-frequency, repetitive calls, much like a siren, transmit finer and over long distances.

Psychobiologist Jaak Panksepp notes that baby rats emit separation cries that could be interpreted as a sign of emotional distress as well every bit a indicate for help and retrieval past the mother. While dog pups whine in a range nosotros can hear, rat pups' calls are in the ultrasound (30-50 KHz) range, besides high for us to pick upward but perfect for communicating at a distance with female parent rats. Rat and dog puppies, just like human being babies, quiet down immediately when placed in close contact with the body of a caretaker or littermate.

Neurophysiologist Paul MacLean suggests that separation cries may be an ancient form of vocalizing in hominids, preceding speech communication. He reports that these cries are like in species from marmosets to humans. Since the primeval species of mammals were probably nocturnal forest dwellers, crying favored survival of infants by helping parents find them quickly at night, in caves, and in holes.

So animals weep, just do they express emotion in doing so? Jeffrey Masson, writer of When Elephants Weep: The Emotional Lives of Animals,^one argues that many animals display sadness. Charles Darwin noted this, besides, in Expression of Emotions in Animals and Man, even comparing emotional facial expressions among several species; but he concluded that none of them cry in the same sense that humans cry. The title of Masson's book is based on popular accounts of elephants that were observed shedding abundant tears in stressful or painful situations. Darwin, too, wrote that the keepers of Indian elephants at the London Zoo reported that the animals would sometimes cry from sorrow.

Nevertheless, the phenomenon, if it exists at all, is then uncommon in animals that nosotros are driven to seek an caption for its centrality and universality in humans. Alas, tears practice not leave fossils; it may be incommunicable to know for certain why a random genetic mutation in the neural organization that controls tears conferred a selective advantage on early on hominid ancestors who wept to limited feelings. But we can begin to seek understanding by exploring crying in the behavior, brains, and civilization of present-24-hour interval Homo sapiens.

Crying to Communicate

A infant'due south face reddens; he closes his eyes; several muscles in his face and forehead contract. He opens his rima oris and emits a continuous, repetitive, wailing sound that tin be counted on to distress every adult within earshot. Someone, well-nigh probably his female parent, comes to the rescue. A comforting caress and a pacifier thrust into his mouth are enough to finish the crying.

Here, crying is clearly communication. Unable as even so to convey their feelings and urges in words, infants cry for help and care. In babies and adults, crying almost ever means that something is wrong: hunger, discomfort, hurting, frustration, grief, sleepiness, helplessness, anxiety, or fear. Children quickly larn that crying gets attention.

While most fathers barely stir in their sleep when their babies cry, mothers awaken instantly. This selective attention starts with a subconscious perception in the brain stalk of the highly distinctive sound blueprint of crying then, controlled by hormones, activates the cerebral cortex. Other sounds do not agitate a mother from her slumber as effectively. A recent report past Jeffrey P. Loberbaum and his colleagues at the Medical University of Southward Carolina and the National Institute of Child Health and Homo Development used functional magnetic resonance imaging (fMRI) to compare the activation of women's brains in response to the crying of a baby and to artificial noises that held no meaning.² Two areas of the women's brains, the cingulate gyrus and the right medial prefrontal cortex, were activated by the crying baby, but not past the random noises. In our development as a species, the cingulate area is an older part of the brain, related to our emotions; in many mammals, it controls parenting behavior. The right prefrontal cortex is involved in our assessment of negative feelings. Another interesting observation is that the crying of an infant stimulates lactation in the mother, probably via the hypothalamus and the pituitary.

Forever Young

We say, "He cried like a infant"—or, condescendingly, "He's a crybaby"—but is crying a persistence of juvenile characteristics throughout life? Both the pattern and frequency of crying change every bit we grow from infancy to adulthood. Later in life, for example, crying functions equally communication less than it does in infants. What remains is emotionally expressive crying in response to hurting, sadness, and grief. This crying is normally not as frequent or as intense every bit in children. Weeping is the most frequent type of adult crying, an attenuated form of crying, without the vocalizations and movements of the whole body present in children. In adulthood, also, nosotros normally prefer to cry alone.

Why do we keep to shed tears as adults? One reply may prevarication in brain development. Humans are said to take a "neotenic" brain, neoteny being the persistence of baby anatomical and physiological characteristics into, and beyond, reproductive historic period. A related phenomenon is "pedomorphism," the preservation of infant features in adulthood. Like babies, man adults have a large, rounded cranium that is disproportionate to our torso size; a flat face; large, prominent optics; teeth of small size and delayed eruption; almost hairless peel; and genital organs on the front of our bodies. So evident is the persistence of these babe characteristics that some argue nosotros evolved by retaining the juvenile features of our ancestors. As Louis Bolk, a German anatomist, has put it: "humans are fetuses who are capable of reproduction." Indeed, the anatomical development of hominids from Australopithecus to Human sapiens reveals a articulate trend of increasing pedomorphism.

The retardation of human development is a scientific fact. Co-ordinate to the late noted evolutionary biologist Stephen Jay Gould, the bodies of mice and humans develop substantially in the same club, but the corresponding stages of development in humans take up to 15 times longer. Humans accomplish puberty at sixty pct to 70 percent of their final body weight; other mammals ordinarily reach it at just 30 percent.

Moreover, since we take such a large, complex brain, most of it develops outside the womb, after birth. Were this not so, gestation would be extraordinarily long and the infant'south head could non pass through its mother'due south nascency channel at delivery, both of which would reduce the female parent's chances of survival. Therefore we are, in upshot, born prematurely, with an incomplete brain— almost bullheaded, deafened, dumb, and without autonomy of posture, movement, coordination, or perception. Primates depend totally on their mothers for life-sustaining treat at least ii years, and partially for many more. Neotenic brains remain highly plastic and susceptible to modification by the environment for many years later nascence, probably until 15 to 16 years of age in humans. This is crucial for our development of intelligence, conscience, memory, and other college cognitive, motor, and integrative functions.

All this suggests the possibility that not just juvenile anatomical features just also many behavioral ones are carried into after adolescence and across. Anthropologist Ashley Montague, who first presented the neotenic hypothesis in his book Growing Young, insisted that crying and laughing are chief among the traits of children that we preserve for life.

Relief or Arousal?

What are the effects of crying? In 1963, American psychiatrist Karl Menninger wrote in The Vital Balance that "weeping is maybe the most human and most universal of all relief measures." The observation applies well to both classic divisions of emotional trigger-happy: tears associated with positive feelings such as joy, and tears associated with negative feelings such as grief. Crying is commonly thought to release emotional tension. Theologian Albert Richard Smith said that "tears are the safety valves of the heart when too much pressure is laid upon it." It is often said that we cry when some internal barrier, a kind of dam, breaks, as in the expression a "well of tears." Psychologist Dalbir Bindra plant that crying episodes soften or misemploy the initial emotional state that triggered them, again suggesting a mood-relieving function.

Is crying, and then, an adaptive response to stress? Do nosotros feel meliorate when we cry at farthermost frustration, tension, stress, nervousness, or grief? A survey past William Frey suggested that this might be truthful: 85 pct of women and 73 percentage of men reported feeling better after crying.^three In another study, scientists sought a common denominator in all the origins and types of emotional tearing. The merely one they institute, afterward analyzing 465 different episodes of crying, was a relationship with requesting or offering help. This would seem to reinforce the evolutionary, or biological, origin of crying behavior in humans. Children feeling hunger, fear, pain, or other discomfort ask for help by crying and experience relief that aid is forthcoming. The authors proceed to speculate that emotional tearing was acceptable equally a sign of suffering because reflex tearing already showed nonemotional trauma or inflammation of the optics. They were, nonetheless, less successful in explaining why tears are associated with positive feelings, every bit well. One possibility is that joy or relief liberates us to recognize and react to stored-up hurting and sadness, so that our tears are actually a reaction to sadness, not happiness.

And then crying could be considered a kind of psychic homeostatic mechanism, returning the body to an emotional equilibrium that has been upset. This "recovery" notion hypothesizes that crying alleviates negative emotions, providing cathartic relief for depression and sadness. Thus, tearing could be thought of as a rebound phenomenon, an exaggerated response in a management opposite that of an initial, destabilizing reaction to an emotion or a demand. A similar procedure is common in cases of stiff activation of the sympathetic nervous organization, for example, the parasympathetic release of urinary and anal sphincters nether extreme stress. Since the lacrimal gland that produces tears is fed past the parasympathetic branches of the seventh cranial nervus, tearing could be a like rebound upshot.

Unfortunately for this hypothesis, in that location is contradictory bear witness. During trigger-happy episodes, our heart rate and sweating increase, suggesting that—far from producing relief—crying occurs in a state of physiological arousal. An arousal hypothesis virtually the role of crying postulates that fierce is used to communicate to a social group that something is non well, that an aversive response is taking place in the organism. This would put crying in the aforementioned category as other sympathetic responses to acute stress, such as when we go pale, our pupils dilate, and our hair rises. Additional evidence for the arousal hypothesis is that prolonged crying seems to be exhausting, leaving us drained of free energy too equally emotion.

Both theories have pros and cons and, as is oftentimes the example, the truth could lie at their intersection. Perhaps during crying we are emotionally aroused in response to particular thoughts or emotions, but, shortly afterward, our crying becomes a rebound or relief phenomenon. A two-gene theory like this is proposed by psychologists Jay S. Efran and Thomas Spangler. In the first stage of crying, they say, tension and emotional arousal (either positive or negative) are created. In the second phase, at that place is a shift to recovery. Does this imply that two distinct psychophysiological responses are at work? Scientists do not notwithstanding know, but ordinary language expresses our sense that there are unlike types of emotional tearing, for example crying from extreme apprehension and sobbing with relief.

Tears and Tears

Whatever the causes of crying, our tears are an excretion of the lacrimal glands, which are situated above the cranial orbits, laterally to the optics. Tears are 98 percentage water, with several electrolytes (giving them their salty sense of taste) and pocket-sized amounts of 45 different proteins.They too comprise immunoglobulins, which are natural proteins produced during an immune response. This suggests that tears have a function in fighting infection, viruses, and bacteria.

Tears accept iii functions: bones (or basal, or "continuous"), reflex, and emotional ("psychogenic"). Basal tears lubricate our eyes. They are excreted continuously in minor amounts, spreading across the exposed surface of the eyes with the assist of the eyelids. Reflex tears are stimulated in larger than normal amounts past irritation or trauma to the heart and have a protective function. For example, when a speck of dust lands on the conjunctiva (the white of the optics), the flow of tears increases, helping to dislodge the intruder and continue the optics from being scratched. Chemical irritants (such equally those in onions) are done out past reflex tearing. Tears too carry a potent antibiotic (lysozyme) that protects the eyes against bacterial infection. Psychogenic tears flow in response to alterations in our mood and emotions. While basal and reflex tears have distinct physiological functions (and exist in practically all animals that accept complex optics), nosotros have seen that it is much harder to embrace fully the functions of psychogenic fierce.

The three types of tears are dissimilar in limerick (for instance, emotional tears are richer in manganese and proteins), simply it is non clear why. William Frey and Muriel Langseth proposed in 1985 that backlog stress-related toxins might exist excreted in emotional tears, simply there is no testify that a person who fails to produce tears when nether stress will develop an internal chemic imbalance, such as that which can occur when other excretory homeostatic systems such every bit respiration and urination are impeded.

Few experiments accept examined the brain structures involved with emotional tears. Both emotional and reflex tears come up from activation of facial nerves, which are continued to the brain stalk, but emotional crying seems, in addition, to call on our higher brain structures.© 2002 Christopher Wikoff

Differences in the chemic limerick of tears may have some other explanation: dissimilar patterns of neural activation of the lacrimal glands. The lacrimal glands are connected to a co-operative of the facial nerve, a part of the parasympathetic division of the autonomic nervous arrangement, which is responsible for decision-making our internal machinery such as the center, glands, vascular system, and bladder.

Inside the Crying Encephalon

Despite the importance of crying as a powerful human emotional expression, at that place accept been few experimental or clinical studies of its basis in our brain and nervous system. At this signal, we know far more than near the low-level neural command of shedding tears than near the upper encephalon structures involved with the emotional aspects. The figure above shows that both emotional and reflex production of tears are brought about past activation of the pair of facial nerves, which in plough accept their neuron jail cell bodies within the brain stem, in the pons and medulla. Information technology is the brain stem that controls our almost basic physiological functions—heartbeat, respiration, blood force per unit area, and so on—and, in terms of evolution, that is the encephalon's oldest office.

Some branches of the facial nerve handle sensory input (for instance, pain sensors in the eyelids); others have a somatic motor function (activating the muscles of the face that contract during crying); and yet others an autonomic nervous function. The two main divisions of the autonomic nervous system, the sympathetic and the parasympathetic nervous systems, are responsible for visceral expression of emotional responses. A study monitoring the psychophysiological reactions of subjects exposed to a deplorable motion motion picture revealed how this happens. Equally subjects began to cry, their respiratory muscles were activated to fill and expel air from the lungs, and movements of the lips, oral cavity, tongue, larynx, and song cords produced crying's typical vocalization. Sobbing requires a convulsive inhaling of air, with spasms of many of these muscles.

Other parts of the sympathetic and parasympathetic nervous systems account for our cherry-red face (by dilation of tiny peel arteries), sweating, increment in claret pressure level and heart rate, secretion of adrenaline and noradrenaline, and activation of the adrenal glands through stimulation of the hypophysis by the brain. This is remarkably similar to the general defense force reaction that we see in response to stress, simply a puzzling question is whether these autonomic and hormonal changes occur as a directly reaction or indirectly, every bit a result of increased somatic action.^iv

While purely basal or reflex tearing takes place at the level of our peripheral nerves and brain stem (and occurs fifty-fifty in severely encephalon-damaged children), emotional crying seems to call on our higher encephalon structures. One clue comes from clinical studies of the exaggerated or pathological crying that accompanies brain lesions. Vikram Patel of London's Maudsley Hospital reports that these studies have helped locate the areas of the cortex that may mediate the emotional component of crying behavior.⁵ He thinks that there must be an interaction between the college cortical and subcortical structures that mediate mood and the cranial nerve nuclei in the lower brain stem that we have discussed.

In humans, i of the subcortical structures that may be involved in crying is the limbic system, which is key in motivation and emotional behavior. Experiments in which lesions are fabricated in mammal brains advise that the cingulate gyrus, an evolutionarily newer part of the limbic system, is involved both in infant crying and in maternal behavior.

In 1980, Panksepp and his group observed the effect of several psychoactive drugs on the distress calls of rat pups. Drugs such as chlorpromazine, reserpine, meprobamate, diazepam, booze, pento-barbital, and amphetamine did not reduce these distress calls when the rat pups were separated from their mothers, but social stimuli such every bit contact with siblings did inhibit them. Opiates such as morphine, however, were strong inhibitors. According to Panksepp, "if you give opiates to animals, they do non weep at all." He suggests that, in inhibiting distress, opioids may act on the same encephalon system as do social contacts.

Through research on the encephalon ground of emotions such as fear and aggression, we know that there are many pathways from the limbic organisation to the hypothalamus, mesencephalon, and brain stalk. We may speculate that these pathways are besides involved in the expression of crying.

Crying on the Right?

Ever since French anatomist and neurologist Pierre Paul Broca discovered that the motor control of language is lateralized, with the brain's left hemisphere predominant, scientists have wanted to know whether emotions are lateralized, too. For more than a century, for example, we have known that when patients sustain damage to one hemisphere of the brain, their emotional reactions modify markedly. An intriguing finding comes from Richard Davidson's 1982 studies of the prefrontal cortex, a encephalon structure crucial in feelings and emotions. Using several brain-imaging technologies, Davidson found that the left prefrontal cortex participates with other structures in a circuit important for certain types of positive emotion.^half-dozen By contrast, activation patterns in the right prefrontal cortex are more often associated with negative emotions, including uncontrollable crying.

Davidson and a co-researcher, Nathan A. Pull a fast one on, discovered that the caste of frontal brain disproportion predicts the nature of an infant's responses to maternal separation. The 10-month onetime babies who cried during brief separation from their mothers showed greater EEG activation in the correct frontal brain, in comparison with the babies who did not cry. The researchers suggest that "frontal brain activation asymmetry may exist a marker for private differences in threshold for reactivity to stressful events and vulnerability for particular emotions."

Crying Across Cultures

Crying is a universal human miracle, but researchers have repeatedly shown that where, when, and how people cry varies not only with their sex, ethnic and cultural backgrounds, and individual psychology, only also with socioeconomic conditions, level of education, family traditions, religious beliefs, and even occupation.

For writer and psychotherapist Jeffrey A. Kottler, "The linguistic communication of tears is hardly a universal form of advice in every part of the globe. People from different places speak unique dialects in their tearfulness and have different attitudes toward emotional expression…Some cultures encourage tearful expression as healthy and socially appropriate in certain circumstances, while others suppress crying with a vengeance."⁷ His expression "the language of tears" implies that crying—a nonverbal, primitive means of expressing ourselves in emotional situations—is a kind of language for communication, and thus learned.

To a large degree, cultural rules learned early in our childhood govern our control over our emotions. It is widely observed, for example, that people from the Mediterranean and Near East (such as Italians, Arabs, and Jews) tend to be less restrained in their emotions than people from Northern latitudes (such as Anglo-Saxons and Scandinavians). Amid the latter, showing tears in public is deterred by the cultural assumption that weeping and crying are manifestations of weakness and inferiority. An farthermost example of this inhibition of crying can exist institute in Asia, where the Minangkabu people of Indonesia are admittedly forbidden to show whatever signs of sadness. They never cry.

Even inside a culture, social rules permitting crying may vary.⁸ In some African cultures, boys undergoing circumcision are forbidden to cry considering they must demonstrate courage and manliness; but when they feel any other kind of hurting, they are encouraged by their mothers to wail their lungs out to indicate danger and call for help.

In all cultures, nonetheless, in that location is potent polarization by sex, epitomized in the phrase "big boys don't cry." This shows how important learning is to the emotional inhibition of men. Generally, women are far less socially controlled in expressing grief and pain by crying and are encouraged to practise so in many social situations, such equally funerals. In the Middle East and southern Italy, for instance, incessant wailing, chirapsia at the head and chest, and tearing at the hair are dramatic postures and behaviors of bereavement that the women at a funeral volition show, and are so stereotyped as to seem to outside observers artificial or forced. For these women, crying is a cultural outcome, expected to occur. If a widow does not weep at the funeral of her husband, or a mother at her child's burial, her social group concludes that she did non dearest them or even that she welcomed their expiry.

Studies of cultural differences in expressing emotion, such as Paul Rosenblatt'south Parent Grief: Narratives of Loss and Relationship, a seminal work on grief and mourning in 78 cultures, reveal that the most effective and universal stimulus for crying is bereavement, particularly grief at losing a loved 1. With few exceptions, funeral rites in all cultures include open up crying. Inhabitants of Bali, still, rarely cry, even in bereavement and pain. Children in Bali may make crying noises, but exercise not shed tears. There are great differences in the ways the predominant religions in the W and Due east care for death. In the United States, for instance, virtually xx percent of crying is related to bereavement; in Japan, simply 5 percent.

Styles of crying range from silent, expressionless tears, to loud weeping and wailing, to continuous or convulsive sobbing. Culture appears to dictate these styles, and when they are used. Kottler cites the Makonde, a Bantu tribe of Tanzania, who cry in explosive, sirenlike bursts. Thus the way people cry appears to be a kind of learned language, an "extension of a culture's native natural language." In fact, American researchers Sara Harkness and Charles Supper, who carried out cross-cultural studies of crying in East Africa, observed that learning when and how to weep can exist said to parallel how language is learned. Upon a biological basis of emotional expression (the lexicon) are imposed the social rules and norms (the grammer) of crying.

Crying and Laughing

What strikes us nearly nearly what we know and practice not know about crying is that this of import human miracle has won scant attending from scientists. We have no credible, overarching model for agreement crying, and, so far, enquiry on the brain mechanisms of crying has been pitifully small.

As a footstep toward one possible model, let us propose an intriguing link betwixt crying and the concepts nosotros discussed in "Our Ancient Laughing Encephalon" (Cerebrum, Fall 2000). Ancient Greek culture symbolized the theater with two masks, one laughing, one crying. Indeed, these are the dominant emotional expressions in human beings, and both accept a communicative role, one positive, one negative. Merely what do they accept in common?

Crying and laughing share cardinal and peripheral expressive mechanisms in our brains and bodies. Both involve a complex interaction amongst the prefrontal cortex, limbic organization, and the muscles and glands of the embryonic 3rd branchial arch. Both also sally as nonverbal communication by babies and after, in modified form, are incorporated into adult behavior. Neither appears abruptly in primate evolution; in nonhuman primates there are analogous behaviors, such as an ape's reaction to tickling and a rat pup's separation cry—although humor and shedding tears to express circuitous emotion are unique to human beings.

The communicative role of crying and tears, as of smile and laughing, is underlined by how hands they are understood by the intended receivers. Konrad Lorenz, a founder of the study of behavior, proposed that the immature anatomical features of children make them cute and likable to adults past means of patterns that have powerful emotional and assistance-eliciting effects. Cartoon animal characters, such as Mickey Mouse, make use of these facial patterns, as Stephen Jay Gould wryly observed. German language ethologist Irenãus Eibl-Eibesfeldt noted that the facial expressions of laughing and crying may be innate "releasing" stimuli, since they can exist represented and recognized based on very few lines (essentially the shape of the mouth and eyes), equally Greek theater masks testify.

Laughter and crying may converge in the early development of our brains. Nosotros crave many years to install intelligence, thought, and language in the immature brain with which we are born. Throughout this extended period, adults are the primary source of life experiences, educational activity, and supervising; children tend to remain receptive to this tutelage, pliable and flexible, until reaching puberty. Natural evolution may have favored children with those traits because they enhanced survival and reproduction.

Crying and laughing persist into after life because they are indispensable in expressing positive and negative feelings, inhibiting aggression, promoting social contact, and eliciting cooperative and helpful behavior. In this may lie the overarching explanation of both. What really matters about crying and laughing is understanding their roles in our lives. They are the unique human being way of expressing strong emotions and convey a sense of commonality among all homo beings.

References

1. Masson, J. When Elephants Cry: The Emotional Lives of Animals. New York. Delacorte Press, 1995
2. Lorberbaum, JP, Newman, JD, Dubno, JR, Horwitz, AR, Nahas, Z, Teneback, CC, Bloomer, CW, Bohning, DE, Vincent, D, Johnson, MR, Emmanuel, North, Brawman-Mintzer, O, Volume, SW, Lydiard, RB, Ballenger, JC, George, MS. Feasibility of using fMRI to report mothers responding to infant cries. Low and Feet. 1999; 10(iii): 99-104.
3. Frey, WH, Langseth, M. Crying: The Mystery of Tears. Minneapolis. Winston Press, 1985.
4. Gross, JJ, Fredrickson, BF, Levenson, RW. The psychophysiology of crying. Psychophysiology 1994; 31: 460-468
5. Patel, V. Crying Behavior and Psychiatric Disorder in Adults: A Review. Comprehensive Psychiatry 1994; 34(three): 206-211.
6. Davidson, RJ, Schwartz, GE, Saron, C, Bennett, J, Goleman, DJ. Frontal versus parietal EEG asymmetry during positive and negative affect. Psychophysiology 1979; 16: 202-203
7. Kottler, JA. The Language of Tears. New York. Jossey-Bass, 1996.
8. Luts, T. Crying: The Natural & Cultural History of Tears. New York. W.W. Norton and Co., 1999.

Source: https://dana.org/article/the-animal-that-weeps/

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