‘The Origins of You’ explores how kids develop into their adult selves

cover of the book "The Origins of You"

The Origins of You
Jay Belsky, Avshalom Caspi, Terrie E. Moffitt and Richie Poulton
Harvard Univ., $35

Everyone has an opinion about what makes people, especially the troublemakers, who they are. Bad parents, bad genes, bad society, bad luck, bad decisions — pick your poison.

Starting several decades ago, four psychologists decided to examine how individuals flourish or flounder over the long run. Instead of jumping into a seemingly endless academic scrum over “nature versus nurture,” they studied how children actually develop over years and decades. Jay Belsky, Avshalom Caspi, Terrie Moffitt and Richie Poulton describe provocative insights from their investigations in The Origins of You.

Developmental researchers acknowledge that many personal and social factors interact throughout life. No single factor can explain, say, why one person pursues a life of crime and another excels in college. Life events and random circumstances tug kids in different directions, making various outcomes more or less probable but never dictating outcomes, the authors emphasize.

Only prospective studies can begin to illuminate the winding paths youngsters travel to become their adult selves. Much of The Origins of You concerns a project — now run by Caspi, Moffitt and Poulton — that has assessed about 1,000 New Zealanders in the town of Dunedin from birth to age 38 (data to age 45 is coming soon). The book also focuses on a study, started by Moffitt and Caspi, that has evaluated more than 1,000 pairs of British twins from ages 5 to 18, as well as another study, in which Belsky was involved, that followed about 1,300 U.S. children from birth to age 15. These investigations are among the few that have assessed a range of psychological and physical measures from childhood into adolescence and beyond.

One intriguing finding from these studies suggests that only certain childhood temperaments influence teenage personality and behavior. Dunedin kids deemed “undercontrolled,” irritable and distractible, at age 3 were typically impulsive and danger-seeking at age 18. “Inhibited” youngsters, however, tagged as shy, fearful and unresponsive to others at age 3, later were generally restrained and passive with others. Those two groups made up just 18 percent of the Dunedin sample.

Children play an active part in shaping their social worlds, likely explaining in large part why these particular childhood temperaments were so closely aligned with later personality, the authors suggest. Long-term Dunedin data indicate, for instance, that undercontrolled kids provoked hostility in parents, peers and teachers. A vicious cycle of rejection by others played out in which undercontrolled youngsters never had opportunities to learn social skills and self-control. Inhibited children, in contrast, avoided chances to make friends in new situations and to stand out academically or socially in school. By young adulthood, these kids had no clue how to influence or lead others.

For the remaining 82 percent of the Dunedin youngsters, the researchers found only weak links between age 3 temperament — say, being outgoing and confident or reserved but willing to interact with others — and personality 15 years later. In those cases, kids were able to connect with adults and peers throughout childhood regardless of temperament.

Later in life, the undercontrolled 3-year-olds faced the worst prospects. Those individuals had volatile, unstable relationships with family, friends, romantic partners and coworkers by age 21; males in that group were especially likely to develop gambling problems by age 32.

Other findings from the three studies cover a lot of ground. Consider the following: Good or bad parenting predicts how girls, but not boys, will relate as adults to their own 3-year-olds. Regular marijuana use starting in the teen years harms mental health far more than physical health. As physical abuse and other childhood adversities add up, individuals become more likely to suffer a rapid decline in many markers of biological age — including immune, kidney and heart function — by their 20s and to suffer from poor health by age 38.

Refreshingly, the authors acknowledge that the science of human development is not advanced enough to make pronouncements about how to raise children. Disappointingly, the authors offer few peeks at their personal backgrounds and how they ended up doing what they do. Despite that gap, and the inability of these findings to address development in non-Western cultures, after finishing the book, I couldn’t help but wonder what will happen as these people, tracked since childhood, enter the second half of their lives.


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