One of the fundamental themes (and a continuing debate) in developmental psychology concerns the continuity or discontinuity of temperament and personality from infancy through the rest of a child’s life and into adulthood.
Some researchers believe that they have found evidence for the continuity of relatively stable personality traits through development. Despite the clear importance of environmental stressors and other random events, the evidence seems fairly clear that the personality traits that dictate the response pattern to such life events in adulthood is fairly predictable based on early childhood temperament.
Schwartz and colleagues, in 2003, investigated amygdalar responses to novelty in adults who had been previously classified as inhibited or uninhibited at age two. (The amygdala, a part of the limbic system, has been shown to be involved in the processing of emotional information.) Children classified as inhibited tend to be shy around people, objects, or situations which are unfamiliar, while uninhibited children tend to approach or even seek out novel people, objects, or situations. They hypothesized that there would be neural differences between the two groups, particularly in response to novel versus familiar faces. The hypothesis was confirmed for this sample, as the two groups had different responses to the stimuli in this fMRI study. One interpretation of these results is that there is continuity in temperament at least to early adulthood, although only a longitudinal study could truly address that question. This study found a correlation between early temperament categorization and adult amygdala activity, which leaves open several possible alternative interpretations.
Caspi, in 2000, gave somewhat more convincing longitudinal evidence that there is developmental continuity of temperament, using data from the Dunedin longitudinal study. In general terms, he found that undercontrolled (uninhibited) three year olds grew up to become impulsive, unreliable, and antisocial, while inhibited three year olds became unassertive and depressed, and had less social support.
More specifically, undercontrolled toddlers were rated by teachers and parents as having more externalizing problems at age 5, 7, 9, and 11. In adolescence (age 13 and 15), the undercontrolled toddlers continued to have externalizing behavior problems, and they showed more internalizing problems as well. The inhibited children had significantly more internalizing problems than the undercontrolled or control groups.
By age 18, the undercontrolled children were low on traits designed to measure constraint. In self-descriptions, terms used included “reckless” and “careless”, and they indicated low harm avoidance. They scored high on negative emotionality measures. They also reported high aggression and alienation. Much of these findings are consistent with the findings from early adolescence. The inhibited children were low on the constraint measurements, and low in positive emotionality. They self-reported high self-control, high harm avoidance, and low aggression. They also reported low social potency – that is, they shied away from leadership roles. Informant ratings at age 21 were consistent with these self-ratings at age 18. Finally, by age 21, undercontrolled children were involved in conflicted relationships; inhibited children had significantly higher social support. Similar significant patterns were also found by age 21 for employment, psychopathology, and criminal behavior.
Ultimately, a considerable amount of data from these studies and others suggest that adult personality is indeed predictable from childhood temperament, but that still does not explain why this is so. A more comprehensive view, accounting for biological, cognitive, emotional, social, and environmental factors, is necessary. Despite the fact that random life encounters cannot be predicted, stable differences in personality likely influences how such events are subjectively experienced.
Schwartz, C. (2003). Inhibited and Uninhibited Infants "Grown Up": Adult Amygdalar Response to Novelty Science, 300 (5627), 1952-1953 DOI: 10.1126/science.1083703
Caspi, A. (2000). The child is father of the man: Personality continuities from childhood to adulthood. Journal of Personality and Social Psychology, 78 (1), 158-172 DOI: 10.1037//0022-3518.104.22.168