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Study links baby’s behavior and adult brain function

Researchers now seek genetic tie

By Carolyn Y. Johnson
Globe Staff / September 6, 2011

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For years, psychologists have debated how much you can tell about who babies will grow up to be from how they act in the high chair. A new study that tracked children from before they were teething until they were graduating high school suggests that a baby boy’s temperament may predict his brain activity nearly two decades later.

Male infants who showed distress in certain situations tended to have elevated activity in their late teen years in a portion of the brain involved in responses to threats or novelty.

Dr. Carl Schwartz, the Massachusetts General Hospital psychiatrist who led the study, and a scientist not involved in the research, were quick to say that the finding doesn’t mean that destiny lies simply in a baby’s disposition.

Rather, Schwartz said, the different signatures of brain activity detected in the study are part of the growing evidence that an infant’s temperament is an important thread in the tapestry of what ultimately makes up a person. He noted that previous studies have found that children with this temperament are in later years more likely to be timid and avoid risks - and to be at greater risk for anxiety disorders, and possibly depression.

“This raises the possibility of early intervention, early risk detection,’’ said Schwartz, director of the hospital’s developmental neuroimaging and psychopathology research laboratory. “It goes to this larger philosophical question: How early in life can we make predictions about who we might be.’’

The research, published today in the journal Molecular Psychiatry, is the latest in a series of findings that have emerged from research spearheaded by Jerome Kagan, an emeritus professor of psychology at Harvard University who has long studied whether elements of a child’s early temperament remain stable later in life.

Researchers followed 135 four-month-old infants until they were 18 years old. Babies that reacted to novel smells, voices, and colorful mobiles with distinctive squirming and distress, arching their backs and fussing - were classified as “high reactive.’’ When the high reactive male infants had grown up and were presented with photos of unfamiliar faces in a brain scanner, researchers tended to see activity flare especially high in the amygdala, a region deep within the brain that has been known to react to threat or novelty. In contrast, those who had been classified as “low reactive’’ generally had less of a response in the amygdala to the novel faces, as did young women who had been classified as “high reactive.’’

“It’s a remarkable finding. Any time you can go from measuring or observing behavior at four months of age to adulthood in one big jump, that’s pretty amazing,’’ said Nathan Fox, a professor of human development at the University of Maryland not involved in the study.

The study raises many questions, which researchers have yet to answer, including why female infants who were also high reactive did not show the same pattern of brain activity as teens - and whether the patterns observed in the scanner are linked to adult behaviors or traits, such as reticence or social anxiety.

Schwartz said that his team hopes to follow the participants of the study into adulthood. He also said that the gender-specific findings raise the possibility that a subset of men may be at higher risk of anxiety or depression.

For their next step, Schwartz and colleagues plan to study the small sample to see if it is possible to discern genetic differences that might account for their disposition as infants, and later brain activity differences.

“We know that these temperaments appear to be heritable,’’ Schwartz said. And because at four months of age, the environmental influence on children is relatively slight, the researchers hope they may be able to pinpoint genetic clues that give rise to the differences.

“We think if this is closer to the elemental biology,’’ he said, “that nature may reveal some of her clues in the genetic code.’’

Carolyn Y. Johnson can be reached at