|Who Do You Think You Are? - Page 5|
The Secret Lives of Babies
Despite Chess and Thomas's precise and detailed typology, many therapists remained unconvinced that traits considered "temperamental" were actually inborn. Couldn't they simply be the outcome of certain early parenting styles? By the early 1980s, theories of infant attachment, social learning, and family systems were in the ascendance, and temperament still carried a faint odor of biological bias. Into this nurture-focused field stepped a curious, observant researcher by the name of Jerome Kagan.
Kagan, then a professor of psychology at Harvard, had been studying infants in daycare to try to determine the impact of out-of-home care on babies' cognitive and emotional development. While observing these babies—some as young as 3 months old—he noticed that some were already timid or even avoidant, while others smiled and cooed in the presence of strangers. He recognized these differences as roughly correlating with Chess and Thomas's "slow-to-warm-up" and "easy" categories, as well as Jung's introverted/extroverted classifications. Gradually, Kagan's observations coalesced into a central question: if temperamental proclivities were showing up as early as 3 months, might they be innate, buried deep within our neurobiology? Around this time, studies had begun to show that identical twins reared apart remained impressively alike in temperament, strongly suggesting a genetic component. But Kagan wasn't content with mere observation of individuals' temperamental tics. He wanted to probe deeper, into the subterranean regions of the brain, for evidence of innate proclivities. By seeking markers of distinctive brain states—specifically, variations in amygdala excitability in response to the unknown—he hoped to come closer to solving the predisposition puzzle. Within a few years, he'd embarked on a project with the potential to alter forever our understanding of human beings—a 20-year longitudinal study seeking to measure both the presence and persistence of inborn temperament.
Kagan and his colleagues began in 1988 by videotaping 100 healthy 4-month-olds as they reacted to a variety of unfamiliar sensory stimuli, including brightly colored mobiles and taped voices of unknown adults. Then Kagan took all 100 videos to a quiet room and began to roll them. The first several infants exhibited moderately varying levels of reactivity to the new stimuli—a little fretfulness here, a bit of cheerful babbling there.