Timid Babies Likely To Be Introverts In Adulthood, Study Finds

WASHINGTON — Could an infant’s temperament predict how the child will behave years later? New research indicates that may very well be the case. Babies who appear fearful of others or demonstrate shyness are more prone to having a reserved, introverted personality in adulthood, a new study shows.

Researchers with the National Institutes of Mental Health (NIMH) say that infants showing a condition referred to as “behavioral inhibition” (BI) may be more likely to struggle socially by age 26. Those with BI tend to act more cautious and avoidant toward any unfamiliar people, objects, and situations. The study also found that children who show increased sensitivity to making errors in adolescence also are on course to develop mental health disorders such as depression and anxiety.

“While many studies link early childhood behavior to risk for psychopathology, the findings in our study are unique,” explains Dr. Daniel Pine, a study co-author and chief of the NIMH Section on Development and Affective Neuroscience, in a statement. “This is because our study assessed temperament very early in life, linking it with outcomes occurring more than 20 years later through individual differences in neural processes.”

Temperament in this context refers to biologically-based individual differences in how people respond to the world emotionally and behaviorally. An infant’s temperament is the foundation of later personality, according to the research team. Previous research has shown that BI is mostly stable from infancy to toddlerhood to childhood. Children with BI have been shown to be at a higher risk of developing social withdrawal and anxiety disorders than other children.

The findings suggest predictable long-term outcomes of inhibited childhood temperament, but there hasn’t been enough research in this area to confirm it.


For the study, the research team recruited participants at four months old. Researchers assessed the infants for signs of BI at 14 months of age. They returned to the lab at age 15, where they provided researchers with neurophysiological data, which were used to assess error-related negativity (ERN), or the degree to which people are sensitive to errors. The researchers looked for a dip in the electrical signal recorded from the brain occurring after incorrect responses were recorded on computerized tasks.

The research team looked for large and small ERN signals. Larger signals have been shown to be indicative of internalizing conditions like depression, while smaller signals are associated with externalizing conditions like impulsivity and substance abuse.

In the final phase of the experiment, participants returned to the lab at age 26 to be assessed for psychopathology, personality, social functioning, education, and employment outcomes.

“It is amazing that we have been able to keep in touch with this group of people over so many years. First their parents, and now they, continue to be interested and involved in the work,” says study author Dr. Nathan Fox of the University of Maryland Department of Human Development and Quantitative Methodology. “We have studied the biology of behavioral inhibition over time and it is clear that it has a profound effect influencing developmental outcome.”

The team concluded that BI indicators at 14 months of age predicted a more reserved personality, fewer romantic relationships over the past ten years, and lower social functioning with friends and family at age 26. BI at 14 months also predicted more internalizing psychopathology in adulthood for those displaying larger error-related negativity signals at age 15. The condition didn’t appear to affect externalizing general psychopathology or with employment and education outcomes.

The study is published in Proceedings of the National Academy of Sciences.

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