The science of introversion and extroversion has always fascinated me. Why are certain people entirely capable of public speaking and acts of confident socialising whilst others are not? Is it a result of our cerebral conditioning? Is it linked to the theory of nature vs. nurture in our childhoods? Both of my parents are loud, outspoken types, so why the difference in our genetic make-up? How can our personalities be so vastly dissimilar?
A group of scientists at Harvard have dedicated themselves to investigating how the framework for our personalities is developed from birth. Jerome Kagan, an eighty-year old developmental psychologist, has devoted his career to analysing the emotional and cognitive development of children. In one particular study, he followed children from infancy through to adolescence, and documented their physiologies and personalities along the way. In 1989, Kagan and his team gathered five hundred four-month-old infants, and predicted that they would be able to tell who would become an introvert or extrovert based on a forty-five minute survey. This may seem like an audacious claim, but the results were astounding.
Kagan exposed the infant to a carefully chosen set of new experiences. The infants heard tape-recorded voices and balloons popping, and were surrounded by colourful mobile devices. They had incredibly varying reactions to the new stimuli. Approx. 20% cried loudly and pumped their arms and legs wildly. This group was named, ‘the high reactive.’ Around 40% of the infants remained quiet and placid, and only pumped their arms and legs occasionally. This group was named, ‘the low reactive.’ The remaining 40% fell between these two extremes. In an incredibly shocking prediction, Kagan predicted that ‘the high reactive’ group would grow into quiet teenagers. He was correct too.
When the infants were two, four, seven and eleven years old, the children returned to Kagan’s lab for follow-up testing. At the age of two, the children were exposed to a lady wearing a gas mask and a lab coat, a man dressed as a clown, and a radio controlled robot. At seven, they were encouraged to play with children that they had not previously met. At eleven, an unfamiliar adult interviewed them about their personal lives. Kagan’s team studied how these children reacted to these strange scenarios. They noted their body language, and recorded how often they laughed, talked and smiled. He also measured their heart rates, finger temperatures, blood pressure, and other properties linked to the central nervous system.
Many of the children turned out exactly as Kagan had predicted. The high reactive infants developed serious and careful personalities. The low reactive infants were more likely to become relaxed and confident types. Kagan’s study is not without flaw, and some may question the ethics behind such studies, but it is clear that stimuli presented during infancy can predict a later personality type, or create it entirely. It is an interesting case for debate, and one that provides a potential insight into how our personality types are developed. I’ve always been a firm believer that our childhood experiences provide the foundations for our lives in adulthood, and this study conveys that it definitely has psychological consequences.