This is the 2007 version. Click here for the 2017 chapter 10 table of contents.


The late 80s saw a flurry of research supporting the idea that temperament is determined more by biology than upbringing or parenting style. Of all the temperamental factors studied, shyness was found to be the most consistent personality trait, from early childhood through adolescence and adulthood. Shyness bears a resemblance to the anxiously attached pattern described by Ainsworth and may well be related to it.

What are advantages and disadvantages of longitudinal studies?

Kagan, Reznick, and Snidman (1988) reported the results of a longitudinal study in which the same children were tested repeatedly from age 2 to 7. Longitudinal studies are the most powerful type of developmental psychology research. Unlike cross-sectional studies, which gather data from people of different ages all at once, longitudinal studies follow the same individuals for many years to see how they develop. Such studies can be very expensive, as well as time-consuming, but they provide superior data about how individuals change.

In this case, shyness was defined as a tendency to become quiet, alert, and emotionally subdued in unfamiliar situations. The researchers were surprised at the high degree of stability in this trait among their subjects. The same children were found to be shy or un-shy at age 2 and age 7.

What did Kagan's research group discover about shyness?

A majority of children who had been selected from a much larger sample at 1.5 or 2.5 years because they were extremely shy, quiet, and restrained in a variety of unfamiliar contexts became 7 year olds who were quiet, cautious, and socially avoidant with peers and adults... (Kagan, Reznick, & Snidman, 1988)

By contrast, children who were extremely sociable and emotionally expressive at age 2 were talkative and outgoing at age 7. Despite the strong evidence for genetic predispositions, Kagan and colleagues did not conclude that shyness was genetically predetermined. They reported a suspicion that "chronic environmental stress" around the age of 2 had something to do with early shyness, which then persisted on its own.

How might the amygdala be involved in shyness?

Kagan and colleagues noted that most of their shy subjects were younger children in multi-child families, while many of the outgoing children were older children. The researchers speculated that older children might contribute to shyness in their younger brothers or sisters through such domineering tactics as grabbing away toys when the younger children were still vulnerable toddlers. However, Kagan and other researchers at Harvard were also aware of the emerging evidence relating the amygdala to emotional regulation (p.450). Kagan and Snidman (1991) proposed a theory of shyness that blamed it on an overactive amygdala (p.90). Obviously the two types of influence-biological and environmental-are intertwined. Biology affects learning, and vice versa. A child with an overactive amygdala might be more likely to develop learned avoidance behaviors, resulting in a shy child.

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