Who was Baby 19?

Baby 19 was the 19th baby tested in a longitidinal study performed by psychologist Jerome Kagan into temperament. The first 18 children in the study were relatively easy going, but when they got to Baby 19 Kagan and his colleagues noticed that they got a different reaction to the new stimuli (for instance a toy). Baby 19's reaction was that of severe anxiety and overwhelming emotion. The child's temperament, along with the others in the study, were tested over a number of years until their mid-teens. Baby 19 and others like her still showed signs of fear and worry years later. But itis not all bad news for parents of Baby 19s.

*More to come*

Reference: "Brain Rules for Baby" by John Medina.

Further information on the study:

From Wikipedia

Alexander Thomas, Stella Chess, Herbert G. Birch, Margaret Hertzig and Sam Korn began the classic New York Longitudinal study in the early 1950s regarding infant temperament (Thomas, Chess & Birch, 1968). The study focused on how temperamental qualities influence adjustment throughout life. Chess, Thomas et al. rated young infants on nine temperament characteristics each of which, by itself, or with connection to another, affects how well a child fits in at school, with their friends, and at home. Behaviors for each one of these traits are on a continuum. If a child leans towards the high or low end of the scale, it could be a cause for concern. The specific behaviors are: activity level, regularity of sleeping and eating patterns, initial reaction, adaptability, intensity of emotion, mood, distractibility, persistence and attention span, and sensory sensitivity. Redundancies between the categories have been found and a reduced list is normally used by psychologists today.[3]
Jerome Kagan and his colleagues have concentrated empirical research on a temperamental category termed "reactivity." Four-month-old infants who became "motorically aroused and distressed" to presentations of novel stimuli were termed highly reactive. Those who remained "motorically relaxed and did not cry or fret to the same set of unfamiliar events" were termed low reactive.[1] These high and low reactive infants were tested again at 14 and 21 months "in a variety of unfamiliar laboratory situations." Highly reactive infants were predominantly characterized by a profile of high fear to unfamiliar events, which Kagan termed inhibited. Contrastingly, low reactive children were minimally fearful to novel situations, and were characterized by an uninhibited profile (Kagan). However, when observed again at age 4.5, only a modest proportion of children maintained their expected profile due to mediating factors such as intervening family experiences. Those who remained highly inhibited or uninhibited after age 4.5 were at higher risk for developing anxiety and conduct disorders, respectively.[1]
Kagan also used two additional classifications, one for infants who were inactive but cried frequently (distressed) and one for those who showed vigorous activity but little crying (aroused). Followed to age 14–17 years, these groups of children showed differing outcomes, including some differences in central nervous system activity. Teenagers who had been classed as high reactives when they were babies were more likely to be "subdued in unfamiliar situations, to report a dour mood and anxiety over the future, [and] to be more religious."[4]

According to Kagan, (conventionally):
"temperament refers to stable behavioral and emotional reactions that appear early and are influenced in part by genetic constitution."[7]
Temperament is perhaps what Kagan is best known for. He began his work on temperament after his research in Guatemala. Kagan was primarily focused on children’s fear and apprehension.[6] It was during this time that Kagan discovered children as having one of two types of temperament: inhibited and uninhibited. Inhibited temperament, also known as highly reactive, can best be described as a child being more reserved, guarded, and introverted whereas uninhibited, or low reactive, children tend to be more outgoing, extroverted, and are very comfortable in social situations.[5] As a result of his ground breaking work on temperament, we know that these characteristics have the ability to influence later behavior depending on how they interact with the environment.[6]

Kagan rejects "attachment theory", British psychiatrist John Bowlby's notion that the bond between caregiver and infant is crucially influential in later emotional and even intellectual growth. He has also criticized Judith Rich Harris's theory that peer groups matter more than parents in influencing the personality of children. He believes that both sides in the nature/nurture debates were too rigid, and that the development of personality is still not well understood.