By Lisa Scott, Ph.D.
The Florida State University
Professionals are becoming increasingly
interested in understanding how child temperament influences various
communication disorders. One of the world’s leading researchers on
temperament, Jerome Kagan, Ph.D., a Daniel and Amy Starch Professor of
Psychology at Harvard University, delivered a fascinating two-hour
seminar entitled, The Nature of Human Temperament at the most recent American Speech-Language-Hearing Association convention.
Dr. Kagan began his presentation by first
defining the difference between temperament, personality, and mood.
Temperament is the child’s biological contribution to his own
emotional, cognitive, and motor profile. In other words, it’s the
emotional reactivity the child is born with, based on his biological
makeup. Personality, on the other hand, is how the child’s temperament
is shaped by environmental influences. For example, children who are
born with more inhibited personalities may be less likely to grow into
anxious, introverted adults if raised in a middle-class environment
versus those who are raised in low-income environments. In fact, Dr.
Kagan emphasized that although temperament is an inherent biological
trait, the child’s environment has been found to have as much or more
influence on how
the child develops than does birth temperament. He
cautioned against looking solely to genetics as explanation for human
behavior. The third factor, mood, is the child’s chronic emotional
state such as happy, worried, or serious, and is heavily influenced by
the child’s temperament.
Evidence from twin studies reveals that an
individual’s likelihood of inheriting a particular temperament is about
50%, but temperament is not the only explanation for our emotional
lives. Your temperament may bias you to respond in certain ways, but
your emotions and reactions are also heavily influenced by the
environment around you.
Temperamental profiles are distinct from one
another rather than occurring on a continuum, and can be identified in
children as early as five months of age. Also, certain developmental
disorders, such as attention-deficit disorder, have their own
temperamental profile.
Dr. Kagan and colleagues have studied two
groups of children extensively, those who exhibit either low-reactive
or high-reactive temperaments. High-reactive children are those who
would usually be described as inhibited or shy children. They
demonstrate high reactivity by being extremely sensitive to anything
new such as new people, rooms, foods, or experiences, and respond to
new stimuli by getting motorically tense. Once the child “understands”
the new stimulus, however, they will often then relax. Interestingly,
when high-reactive 11- to 15-year-olds complete personality
questionnaires, they will describe themselves as worriers, more
serious, and less likely to smile or laugh than their peers. These
self-reports were confirmed by observations of the researchers who
interviewed the children.
In contrast, children who are low-reactive,
or uninhibited children, are more social, exuberant, and likely to
express positive emotions. Compared to the high-reactive 11-15 year
olds, low-reactive children in this age group described themselves as
happy, easy-going, and less serious than others their age.
Dr. Kagan went on to describe results from a
number of studies investigating whether differences between the groups
exist in brain function, heart rate, and on other physiological
measures. He emphasized the role of the amygdala, a brain structure
that is responsible for the intake of sensory information and then acts
like a “fire department” to send communication to about 80% of the
brain.
Kagan and colleagues’ hypothesis is that
high-reactive children inherit a neurochemistry that takes very little
to fire up the amygdale, which in turn creates tension in their bodies.
He also shared his hypothesis that high-reactive temperaments may be
noted more frequently than other temperament profiles in children who
stutter, those who exhibit selective mutism, and those children who
don’t make as much progress in therapeutic relationships.
Dr. Kagan concluded his seminar by stating
that our current understanding of temperament is equivalent to how well
diabetes was understood in 1750; in other words, we have much to learn
about this important developmental factor and its role in how children
develop and interact with their environments.
