11.3 Temperament and Heredity
11-3 What have psychologists learned about temperament?
As most parents will tell you after having their second child, babies differ even before gulping their first breath. One aspect of personality—temperament (emotional reactivity and excitability) is quickly apparent, and it is genetically influenced (Kandler et al., 2013; Rothbart, 2007). From their first weeks of life, some infants are noticeably difficult—irritable, intense, fidgety, and unpredictable. Others are easy—cheerful and relaxed, feeding and sleeping on predictable schedules. Still others tend to be slow to warm up, resisting or withdrawing from new people and situations (Chess & Thomas, 1987; Thomas & Chess, 1977).
Consider how researchers have studied these issues with LaunchPad’s How Would You Know If Personality Runs in the Genes?
Temperament differences typically persist. Consider:
- The most emotionally reactive newborns tended also to be the most reactive 9-month-olds (Wilson & Matheny, 1986; Worobey & Blajda, 1989).
- Exceptionally shy 6-month-olds often were still shy as 13-year-olds; over 4 in 10 children rated as consistently shy developed anxiety problems in adolescence (Prior et al., 2000).
- The most emotionally intense preschoolers tended to be relatively intense young adults (Larsen & Diener, 1987). In one study of more than 900 New Zealanders, emotionally reactive and impulsive 3-year-olds developed into somewhat more impulsive, aggressive, and conflict-prone 21-year-olds (Caspi, 2000).
- Identical twins, more than fraternal twins, often have similar temperaments (Fraley & Tancredy, 2012; Kandler et al., 2013).
The genetic effect appears in physiological differences. Anxious, inhibited infants have high and variable heart rates and a reactive nervous system. When facing new or strange situations, they become more physiologically aroused (Kagan & Snidman, 2004; Roque et al., 2012). One form of a gene that regulates the neurotransmitter serotonin predisposes a fearful temperament and, in combination with unsupportive caregiving, an emotionally reactive child (Raby et al., 2012).