Communication disorders and temperament

From the Stuttering Foundation's winter 2008 newsletter

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.