Saturday, July 01, 2000

Can Mother Love Grow Synapses?

The Biology of Love

By: Jerome Kagan Ph.D.,


The human mind, allergic to complexity, yearns for simple ideas to explain nature’s puzzles. Explanations of the dramatic variation in human mood, thought, and behavior have cycled between embarrassingly simple biological or experiential accounts. In ancient Greece, the physician Galen explained moods in terms of four humors in the body (blood, phlegm, yellow bile, and black bile) and the balance among them—an account that remained popular right to the end of the nineteenth century. In contrast, during the first quarter of the 20th century, the desire to blame the academic failures of large numbers of American children of European immigrants on social disadvantage, not on genes, required a total rejection of biological explanations. The environmental biases of psychoanalysis and behaviorism were seen as compelling. In reality, however, even these supposedly complex systems of explanation were far more simplistic than the data meteorologists must manipulate to predict tomorrow’s weather. 

Despite this seesaw history, most people assume that our society is blessed with a cadre of exceptionally insightful experts who understand the major problems of the day. Until the first world war, the public was ready to encounter this understanding of human nature and society in the proclamations of novelists, historians, social scientists, and biologists. Dramatic discoveries in molecular biology and neuroscience over the past 25 years, however, have rapidly elevated natural scientists into our preferred arbiters of truth about matters related to parenting, education, and mental health. Teachers seeking guidance on curricular reform and parents looking for the best way to raise their children assume neuroscientists have critical facts that, translated into practice, will do the trick. 

In reality, there are relatively few situations in which research from biology laboratories has significant, solid implications for social issues; and even those implications must be applied carefully. For example, infants born with cataracts should have them surgically removed as soon as possible so that they can receive patterned visual stimulation. This advice is based on the Nobel prize-winning experiments of David Hubel and Torsten Wiesel1 on kittens, and more recent work on infants by Daphne Maurer2 of McMaster University. But these hard-won discoveries do not imply that infants with normal hearing and vision must listen to Mozart or watch flash cards to develop a normal brain. Most children born with intact sensorimotor systems get adequate daily sensory stimulation. 

Nevertheless, increasing numbers of Americans and Europeans are ready to treat as possibly true the heady claims, first, that every experience has a permanent effect on the brain and, second, that brain processes are directly related to behavior. Marry these two assumptions to a third—that early experience has a special priority (a Puritan notion announced regularly from 18th century pulpits on Sunday mornings)—and you have the core of Arthur Janov’s argument in The Biology of Love.

A California psychotherapist, Janov achieved celebrity by suggesting in his 1970 book, The Primal Scream, that patients can ease the neurotic symptoms of repression by literally screaming out their anguished thoughts in the consulting room. Now, in The Biology of Love, Janov warns that if parents do not love their infant, the infant’s brain, and the future psychological integrity of this innocent life, will be compromised forever. If true, this should be every parent’s mantra. Janov’s hypothesis is very probably false, however, and the effect of his book may be to create unnecessary worry in well-intentioned mothers and fathers unsure about the intensity and quality of their affection for the new member of the family. 

Although most parents understand that love for their child is a private feeling, surprisingly, Janov defines it materially. Love, he announces, “means proper breast feeding and holding and touching with warmth,” and “If there is love, the neurons expand, arming the brain against later adversity.”

In making these assertions, Janov ignores a major change in the meaning of parental love that occurs when children, by their fourth birthday, have identified to themselves in words how much their parents value them. Their judgments have little to do with the frequency with which parents caressed the child several years earlier. Many accomplished adults—John Stuart Mill and Charles Darwin are famous examples— wrote that they perceived their fathers as cold and aloof but were certain that they loved their sons. Mill confessed that he was loyally devoted to his father and hesitant “to pronounce whether I was more a loser or a gainer by his severity.”3 In contrast, the impoverished, isolated Mayan Indians of Northwest Guatemala, with whom I worked 30 years ago, nursed and touched their infants regularly during the first year. Sadly, despite the material love they received as infants, most adults in these villages were angry, dour, and suspicious, and the men often abused their wives. Every romantic partner, in fact, knows that the feeling of being loved is subjective, not reducible to specific actions by the lover.


Janov’s central thesis in The Biology of Love rests on two ragged premises. The first is that early maternal care affects the infant brain permanently. The second is that there is a direct relationship between this initial impact on the brain and later psychological outcomes.

In contrast to Janov’s claims, many experiments have demonstrated that there is an indeterminate relation between brain events and psychological states. In one study, adults watched an emotionally negative film through an apparatus that let the investigator show the film to either the right or left hemisphere of the subject’s brain. When the film was presented to the right hemisphere, cortisol and blood pressure—two physiological markers of stress— rose higher than when the same film was presented to the left hemisphere. Despite these responses based on brain activity, the subjects did not report that they experienced greater arousal or distress when they saw the film with the right, rather than the left, hemisphere.4 We must conclude from this that their conscious psychological state did not correlate with their brain’s reactions, which is not possible if our thoughts and feelings are tied deterministically to brain events. 

In fact, however, there is a sliver of indeterminacy between psychological and biological events. No matter how powerful brain scanning machines become, scientists will not be able to infer what you are thinking, either the mathematical equations you imagine or the tunes you recall (although it may become possible to know that, as you lie in the scanner, you are generating mathematics rather than melodies). The language we use to describe basic brain processes is simply not translatable into the language we use to describe the thoughts that emerge from those processes. Confident prediction of a person’s beliefs and feelings from neuronal activity is probably impossible. 

The language we use to describe basic brain processes is simply not translatable into the language we use to describe the thoughts that emerge from those processes. Confident prediction of a person’s beliefs and feelings from neuronal activity is probably impossible. 

In fact, eminent brain scientists admit without apology that they are not close to understanding the brain bases for behavior as simple as a rat’s choice of direction in a T-maze.5 There is even a poor correspondence between an activity as basic as the speed with which a monkey moves its eyes to a spot of light and the rate of change in electrical activity in the neurons that permit the eyes to move.6 Equally puzzling is the discovery that corticotropin releasing hormone (CRH) in the brain, usually secreted under stress, increases equally when a rat is allowed to eat and when it is restrained.7 If unpleasant bodily restraint and the pleasure of eating produce equal increases in brain CRH, it is fair to conclude that an understanding of the relation of brain activity to psychological state remains fragile. So, like it or not, it is impossible at present to know what happens in an infant’s brain when a parent plays with the infant; if change does occur, it is impossible to know how permanent it is. Psychological events—smiling, crying, laughing, playing—are not equivalent to activities in neurons, synapses, and circuits.


Janov’s claim that the effects of early experience have a special priority, that what they produce in the brain is most likely to be preserved, is also probably false. For example, the orphans left by World War II and the Korean conflict did not get the mother’s love that Janov regards as critical in the infant years. Yet many of these children developed normally after being adopted by nurturing foster parents.8 In a Canadian study, a group of two- to four-year-old children who had spent the infant years in an overcrowded institution with too few caretakers were enrolled for two years in regular play sessions with adults and children. In time, the initial apathy and indifference lifted, and the typical vitality of 4-year-old children emerged.9

Equally convincing is a study of Swiss children born to unmarried, poorly educated immigrants. These children spent their first year living in an impoverished nursery where stimulation was minimal and caretakers changed often. When the children were reexamined at age 14, most of them had average intelligence and several friends. The few who were extremely unhappy or anxious had been physically abused or spent their post-infancy years with parents who quarreled often. Those who had gone from the depriving nursery to benevolent homes, however, did not show the same level of anxiety, suggesting it was attributable to experiences that occurred after leaving the nursery.10 Finally, scientists who followed 89 middle-class Ohio children from birth to adulthood discovered that the few who displayed serious psychological symptoms in early adulthood had not experienced atypical nurture during their first two years.11 Studies like these led eminent child psychiatrist Michael Rutter to note, “The ill effects of early trauma are by no means inevitable or irrevocable...the evidence runs strongly counter to views that early experiences irrevocably change personality development.”12 

The thousands of infants born this day across the world will grow up in very different environments during their first two years. Some will be raised by surrogate caretakers on kibbutzim, some will be cared for by grandmothers, some will attend daycare centers, some will remain at home with their mothers. Some will have many toys; some will have none; some will spend the first year in a dark hut, wrapped in old rags; some will crawl in brightly lit rooms with toys and television images. Despite this variation (and excluding the small proportion with serious brain damage or genetic defects), most will speak before they are two years old, become self-conscious by their third birthday, and assume family responsibilities by eight years of age. The differences among these millions of children are trivial compared with the long list of similarities. This well-established observation is inconsistent with awarding primary significance to the first year of life.

Why does early experience not predict the future? The brain is immature during the first year of life. The infant’s brain has many more synapses than it needs; during the early years many are eliminated. This pruning is incomplete in the first year of life. Also, the connections between the frontal lobes and the rest of the cortex are still forming. Finally, the right and left hemispheres communicate inefficiently because the fatty sheath of myelin that covers the nerve fibers connecting the two hemispheres is still being laid down. As a result, the infant does not fully evaluate emotional experiences; many early memories are lost. In fact, most adults cannot recall any event that occurred before their third birthday. 

The doctrine of infant determinism is also inconsistent with the discovery that infants are primarily influenced not by particular adult actions but by events that are at odds with their usual experience. An infant fed every four hours by a mother who is following her doctor’s orders— a regimen recommended by pediatricians in the 1930s —will, other things being equal, be no different from infants fed every time they cry. But infants fed on an irregular, unpredictable schedule might develop maladaptive habits. 

A final observation that contradicts infant determinism is that children are affected primarily by how they interpret what happens to them. Millions of Chinese children during Mao Tse-tung’s reign spent most of every day with surrogate caretakers in austere rooms without many toys. These children did not conclude that their mothers did not love them; but that is what children in communities in which few attend daycare centers might conclude. It is the child’s interpretation, not the fact of having a surrogate parent, that has greater weight in shaping development. Because infants are unable to interpret their experiences symbolically the way they will when they are older, events of the first year may have little relation to their later belief that they are loved. 

Because infants are unable to interpret their experiences symbolically the way they will when they are older, events of the first year may have little relation to their later belief that they are loved. 

Counter to Janov’s intuition that memories of infancy prevail, consider this statement from a 37-year-old man who spent his first three years as an orphan in a Nazi concentration camp. He told an interviewer, “I feel more secure now than I ever did…I have two people who really care about me…I know if something happens to me, I have somebody to turn to.”14


Many factors shape adolescents and young adults long after infancy, factors ignored by proponents of infant determinism such as Janov. Three of these are birth order; identification with family, class, and ethnic group; and historical events.

The child’s birth order in the family, especially if the age between the child and the next older or younger sibling is less than four years, influences some psychological qualities, particularly attitudes toward legitimate authority. First-born American children, about 40 percent of the population, are more likely to have a benevolent, respectful view of authority, while the view of later-born children is more apt to be skeptical, even cynical.15 As a result, the eldest child in the family is more disposed to adopt the family’s values. If those values are also the values of the culture at large, a first born will be more receptive to them than later born children. First-born children from middle-class American homes earn better grades than their siblings, as do middle-class only children. First-born and only children are more often high-school valedictorians, and more likely to be listed in Who’s Who in America.

Most school-age children believe they are more like their parents than anyone else. Identifying with his parents, a child will feel enhanced if his parents’ traits are desirable ones. When they are not, the child is vulnerable to feelings of shame or impotence.

To this, adolescents add identifications with their class, ethnicity, and religion. The more distinctive a group is, the greater its power to evoke this sense of identification. Being poor in America stands out more today than it did a century ago; therefore a child’s identification with a poor family can generate shame or anger— and perhaps a chronic physiological state that contributes to the sad fact that the poor have more illness than the middle class. Although the poor do have less easy access to good medical care, experts do not believe this is the only reason for their higher rate of morbidity.

Finally, wrenching historical upheavals can influence adolescent minds. Brain changes emerging at puberty usher in a maturing of the ability to reason and move adolescents to brood on their beliefs. For the first time they grasp that current experiences do not completely align with childhood assumptions. Events like economic depression or war stir young men and women to contrast their beliefs with what they are experiencing. Some wonder why, if God exists, so many people suffer. The Great Depression in America from 1930 to 1940 left about one-third of American families chronically anxious over their economic security. A large proportion of Americans who were adolescents during the Depression saved more money than the generation before or after them and conducted their lives with a continuous, often gnawing concern about financial loss. Today, youth living in Bosnia or Kosovo have witnessed cruelties that will make deep skeptics of their generation. It will make little difference to an 18-year old in Kosovo whether or not she had a caring or an indifferent mother if she has lived through rape, artillery shells, and the senseless death of friends and family.

Birth order, group identifications, and historical context can shape the personalities of older people but are of little or no relevance during the first two years of life. Perhaps that is why neuroscientist William Greenough wrote, “To focus upon the first three years and to downplay the later years is not warranted by either human behavioral or neuroscience research.”


Parents in every culture face chronic uncertainties, although their content varies with time and place. The future status of most children born to Medieval European families was fixed by their birth; most parents worried about infant health and salvation rather than an infant’s future vocation or social position. By the end of the 18th century, when social mobility became common, the future status and psychological health of children replaced earlier parental preoccupation with morbidity and grace.

Every generation of parents longs for expert advice. Puritan parents were told they should break their child’s will. But if contemporary Boston parents were as harsh with their children as their counterparts were two centuries ago, they would be jailed for child abuse, even though Puritan children developed profiles that were well adapted to their particular cultural setting:

Reverend Francis Wayland, an early nineteenth century Baptist minister and President of Brown University, described with pride how he conquered the will of his 15-month-old son Heman by locking him in a closet because the boy rejected a piece of bread the father offered him. When the young boy apologized, almost 24 hours later, the father wrote, “He was completely subdued…Since this event, his disposition is as it has never been before, mild and obedient and evidently much happier than when he was determined to have his own way.”17

In the 1920s, behaviorist psychology pioneer John Watson18 told American parents that they had less than a decade to sculpt their children by using the proper administration of rewards and punishments; Watson did not mention maternal love. Forty years later, John Bowlby19 encouraged parents to establish an emotional bond with their infant. Many American women who became mothers after 1960 trusted that advice and worried that they may have compromised their child’s future happiness by missing their chance to create this unique relationship.

Most parents love their children. They try to build habits and values that will enhance the child’s future in their particular society. If we exclude parents who seriously neglect their infants (fewer than one in 20 American families), there is no scientific basis for the idea underlying Janov’s book and other popular current guides for parents—that variation in how parents behave during the first year systematically affects variation in the biological integrity of their child’s brain. It is true, of course, that parents can influence their children’s scores on tests of language, reading, and arithmetic at the time they enter school. Children raised by parents who read to them regularly will have an advantage over peers who miss this experience. But that does not mean those children have better formed brains. 

Biological facts, for the most part, cannot translate into advice to parents about rearing children. The goals of parents for their children rest on ethical premises that change with time and culture. Facts can prune the tree of morality; they cannot be its seed bed.

Scientists and non-scientists alike must strive to keep pleasing ethical ideals separate from empirical facts. Brain research will be able to tell us, eventually, how the maturing brain sets the stage for the emergence of universal psychological milestones such as stranger and separation fear, language, guilt, and the ability to detect logical inconsistencies. Research may also illuminate the physiology that predisposes people to particular personality traits. But these biological facts, for the most part, cannot translate into advice to parents about rearing children. That is simply because the goals of parents for their children rest on ethical premises that change with time and culture. Facts can prune the tree of morality; they cannot be its seed bed.

I believe the reasons for variation in adult happiness, anger, or despair will always remain a partial mystery, because early temperament, patterns of identification, birth order, historical events, and chance all combine with parent behaviors and personalities to affect an adult’s chronic mood. Ironically, the belief that one is happy today involves a comparison with the past, so a little angst in childhood probably weights that comparison in favor of affirming present happiness. Happiness, confidence, the ability to love deeply, and the ability to work creatively—ethical ideals in America today—are complex psychological outcomes. They are not the result of brain states established by maternal love during the first year of life. Thus, Janov’s claim that when love is unavailable early in life, a person’s capacity to receive and give love will be diminished forever is a serious exaggeration.


From The Biology of Love by Arthur Janov. ©2000 by Arthur Janov. Reprinted with permission of Prometheus Books.

Love is the central ingredient in building and strong and resilient personality. It equips us with the mobilizing chemicals such as dopamine that allow us to be aggressive, to establish goals and pursue them, to stand up for ourselves and have the energy to accomplish things. It accounts for self-confidence, a “can do” attitude. It prevents the need for drugs later on, such as cocaine, that do what dopamine should have done had there been adequate supplies; had there been adequate love.

Emotional deprivation, lack of physical closeness, just after birth reduces the number of serotonin receptors, part of the gating system against pain. So pain stimulates the inhibitory system, while too much early pain cripples it. There is some research evidence that this may lead to introversion, an inability to express feelings, low self-esteem, and general lack of emotional control—in effect, permanent brain dysfunction.

The expression of emotional warmth from the caregiver over time inhibits the production of stress hormones in the baby. This makes the baby more emotionally solid. As a result, the child is not so easily overcome, does not overreact, and can handle more stress than children who did not have this early love. The child is not overcome by a homework assignment and can concentrate on her studies.

Emotional deprivation early on affects the right side of the brain—the emotional side—and can impair it for a lifetime. Because the right side of the brain—the side that governs our emotions and human interaction—is most affected by free-floating cortisol (the hormone excreted when we are stressed), it is the side that suffers the most damage from early stress, and possibly that stress may be due to the change in dopamine secretion. Thus, the right brain, being developed earlier than the left absorbs the impact of preverbal, brainstem targeted trauma.

When there is not enough dopamine secreted to keep the frontal cortex intact we become disorganized, suffer from attention deficit disorder (ADD), grow emotionally labile, and experience states of anxiety and panic. Small infants of depressed mothers, for example, show a right-side frontal asymmetry of the brain. One part of the brain is doing too much work, and it suffers. This may be how later in life we become intellectuals, the left cortex concocting notions and ideas to combat feelings in the right. It is the right that contains much of our early lack of love.

There is also evidence of a lack of balance in dopamine in the amygdalae, which is in some ways the seat of feeling in the brain. Children who were not close to their parents in the first months of life have less dopamine receptors in the limbic area. Alan Schore espouses that nearly all later psychological pathology can be traced to early maternal deprivation after birth. We must push the envelope further back to prebirth events. Intrauterine trauma has a devastating impact on brain development, particularly on the right side. One simple study of a group of students at Harvard some years ago asked them if they were close to their mother or father growing up. Those who were not close to either parent unanimously had serious physical ailments.

When love is not made available early in life, the system “shrinks” and, figuratively, does not develop the proper “love receptors.” The capacity to receive and give love will be diminished for a lifetime. In this sense, love is not an abstraction but a literal neurochemical event. 


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Joseph T. Coyle, M.D., Harvard Medical School
Kay Redfield Jamison, Ph.D., The Johns Hopkins University School of Medicine
Pierre J. Magistretti, M.D., Ph.D., University of Lausanne Medical School and Hospital
Robert Malenka, M.D., Ph.D., Stanford University School of Medicine
Bruce S. McEwen, Ph.D., The Rockefeller University
Donald Price, M.D., The Johns Hopkins University School of Medicine

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