Early Childhood Behavior Predicts Adult Temperament, 26-Year Study Finds

At 14 months, children may already be exhibiting temperaments that offer a glimpse of their future personalities.

According to a longitudinal study published in Proceedings of the National Academy of Sciences, behavioral inhibition at 14 months predicts a more reserved, introverted personality at age 26. Behavioral inhibition—characterized as aversion to anything new or unfamiliar and timid behaviors—was also a risk factor for internalizing psychopathologies, such as anxiety and depression, in adulthood.

“This finding shows that temperament and its underlying biology plays an important role in terms of how we think about the development and expression of personality over the lifespan,” said Nathan Fox, Ph.D., a distinguished professor in the University of Maryland Department of Human Development and Quantitative Methodology.

National Scientific Council on the Developing Child

Fox and his colleagues began examining the influence of infant temperament on socioemotional development almost 30 years ago. They recruited 165 infants between 1989 and 1993 and observed the children’s behavioral inhibition at 14 months in the laboratory, exposing them to three episodes during which mothers were present: a free-play session in an unfamiliar playroom, with an adult stranger, and with a novel toy robot. The researchers observed and coded the children’s responses to create a measure of behavioral inhibition, including how quickly they touched new toys, vocalized during free play, approached the stranger, and other reactions.

Then, 115 of the participants returned to the laboratory at age 15 so researchers could assess error-related negativity, the degree to which individuals are sensitive to errors. Sets of five letters, such as SSHSS or HHSHH, were flashed on a screen and participants were asked to identify the middle letter as quickly as possible. Simultaneously, researchers collected electroencephalography (EEG) data. Error-related negativity was shown as a negative dip in activity in the mediofrontal cortex within milliseconds of making an incorrect response.

Finally, 109 of the participants completed a series of questionnaires when they were 26 years old. The questionnaires assessed the participants’ psychopathology, personality, social functioning with friends and family, history of romantic relationships, highest level of education, and employment status.

The authors found that higher levels of behavioral inhibition early in life predicted a more reserved personality and lower social functioning with friends and family at age 26. Higher behavioral inhibition was also associated with fewer romantic relationships in the past 10 years, though it was not related to whether the participants were in a current relationship at age 26. Behavioral inhibition did not predict education or career attainment.

Behavioral inhibition at 14 months also predicted internalizing psychopathology at age 26, but only among those who showed greater levels of error-related negativity at age 15. Increased error monitoring “might reflect a rigid and ‘over-controlled’ response pattern that hinders social interactions across development among temperamentally inhibited individuals,” the authors wrote.

The authors noted some limitations to the study, including the small sample size and that the participants were primarily Caucasian who grew up in middle- to upper-middle-class families.

“It’s remarkable and powerful that this temperament, which we assessed in infancy, has such a powerful effect on personality over such a long period of time,” Fox said. He emphasized however, that not all children who exhibit behavioral inhibition go on to develop an anxiety disorder or depression. “The environment plays a powerful role in terms of either moderating or exacerbating temperament,” he said.

But further understanding of how behavioral inhibition predicts internalizing psychopathology in adulthood could have implications for intervention, noted Alva Tang, Ph.D., the study’s lead author and postdoctoral fellow in the University of Maryland’s Child Development Lab, of which Fox is the director.

Parents and clinicians often begin thinking of a child’s long-term physical heath during infancy, explained co-author Daniel S. Pine, M.D., chief of the section on development and affective neuroscience in the National Institute of Mental Health (NIMH) Intramural Research Program. “This work shows that people should really start thinking about mental health right at the beginning of a child’s life, as well,” he said.

This research was supported by funding by NIMH and a postdoctoral fellowship from the Social Sciences and Humanities Research Council of Canada. ■