Lifespan Development. Tara L. Kuther

respond more negatively and show more behavior problems than do those with easy temperaments (Poehlmann et al., 2011).

      An infant’s temperament may be stable over time because certain temperamental qualities evoke certain reactions from others, promoting goodness of fit. Easy babies usually get the most positive reactions from others, whereas babies with a difficult temperament receive mixed reactions (Chess & Thomas, 1991). For example, an “easy” baby tends to smile often, eliciting smiles and positive interactions from others, which in turn reinforce the baby’s “easy” temperamental qualities (Planalp, Van Hulle, Lemery-Chalfant, & Goldsmith, 2017). Conversely, a “difficult” baby may evoke more frustration and negativity from caregivers as they try unsuccessfully to soothe the baby’s fussing. Researchers found that mothers who view their 6-month-old infants as difficult may be less emotionally available to them (Kim & Teti, 2014). Babies’ emotionality and negative emotions predict maternal perceptions of parenting stress and poor parenting (Oddi, Murdock, Vadnais, Bridgett, & Gartstein, 2013; Paulussen-Hoogeboom, Stams, Hermanns, & Peetsma, 2007). Goodness of fit at 4 and 8 months of age predicts a close bond with caregivers at 15 months (Seifer et al., 2014).

      Temperament can also be related to mothers’ own temperament, as well as their expectations about their infants and their ability to parent (Grady & Karraker, 2017). In one study, mothers who, prior to giving birth, considered themselves less well equipped to care for their infants were found to be more likely to have infants who showed negative aspects of temperament, such as fussiness, irritability, and difficulty being soothed (Verhage, Oosterman, & Schuengel, 2013). This suggests that perceptions of parenting may shape views of infant temperament—and thereby shape temperament itself. In other research, 3 months after giving birth, new mothers’ feelings of competence were positively associated with infant temperament. Mothers’ beliefs about their ability to nurture are shaped by the interaction between their infants’ traits and their own parenting self-efficacy, as well as their opportunities for developing successful caregiving routines (Verhage et al., 2013). This contextual dynamic has been found to hold true across cultures. Both British and Pakistani mothers in the United Kingdom reported fewer problems with their infants’ temperaments at 6 months of age when the mothers had a greater sense of parenting efficacy and displayed more warm and less hostile parenting styles (Prady, Kiernan, Fairley, Wilson, & Wright, 2014).

      As mentioned earlier, socioemotional development is a dynamic process in which infants’ behavior and temperament styles influence the family processes that shape their development. Sensitive and patient caregiving is not always easy with a challenging child, and adults’ own temperamental styles influence their caregiving. A poor fit between the caregiver’s and infant’s temperament can make an infant more fussy and cranky. When a difficult infant is paired with a parent with a similar temperament—one who is impatient, irritable, and forceful—behavioral problems in childhood and adolescence are likely (Chess & Thomas, 1984; Rubin, Hastings, Chen, Stewart, & McNichol, 1998).

      The most adaptive matches between infant temperament and context can sometimes be surprising. Consider the Maasai, an African semi-nomadic ethnic group. In times of drought, when the environment becomes extremely hostile, herds of cattle and goats die, and infant mortality rises substantially. Under these challenging conditions, infants with difficult temperaments tend to survive at higher rates than do those with easy temperaments. Infants who cry and are demanding are attended to, are fed more, and are in better physical condition than easy babies, who tend to cry less and therefore are assumed to be content (Gardiner & Kosmitzki, 2018). Thus, the Maasai infants with difficult temperaments demonstrate higher rates of survival because their temperaments better fit the demands of the hostile context in which they are raised. Early experience can influence emotional development through biological means, as described in the Brain and Biological Influences on Development feature.

      Brain and Biological Influences on Development

      Trauma and Emotional Development

      Experiencing adversity early in life may have epigenetic effects on the genes that regulate responses to stress. The caregiving environment also influences the developing stress response system and can buffer the negative effects of trauma.

      iStock/jhandersen

      Can infants remember early life experiences? Does exposure to adversity, such as maltreatment, poverty, and violence, influence infants’ development? Very young infants likely do not recall specific experiences and events, but early exposure to trauma may affect infants’ development in ways that can last a lifetime. For example, maladaptive contexts may pose risks of physical harm to children, directly influencing neurological development. However, trauma also poses invisible long-term risks to children’s emotional development and mental health (Blair, 2010).

      How does early trauma effect emotional development? The experience of early social adversity may have epigenetic effects on the genes that regulate the endocrine system, which controls hormone production and release at all ages in life (Conradt, 2017). Infancy may be a particularly plastic time in development with heightened potential for lifelong epigenetic changes that may sensitize responses to stress throughout the lifespan (Laurent, Harold, Leve, Shelton, & Van Goozen, 2016). For example, research with adults reveals that childhood maltreatment is associated with an increased stress reactivity in adulthood (Turecki & Meaney, 2016).

      However, not all infants respond to early life stress with heightened reactivity. Some infants exposed to trauma show lower levels of stress hormones and reduced reactivity to stress (Turecki & Meaney, 2016). The timing and intensity of adversity influences developmental outcomes. Exposure to particularly intense chronic stress early in development can lead to hyperactive stress responses that may be followed by blunted responses (Laurent et al., 2016). Blunted responses may reflect adaptations to chronically stressful situations. Unpredictable stressors, on the other hand, may lead to heightened stress reactivity as the individual adapts to volatile and unexpected situations (Blair, 2010). Both heightened and blunted stress responses may be adaptive attempts to optimize survival in nonoptimal caregiving environments, yet these adaptations may carry behavioral costs, such as heightened distress when confronted with stress and longer term anxiety and depressive symptoms, which negatively affect developmental trajectories (Laurent et al., 2016).

      Early life stress poses risks to emotional development, but the caregiving environment also influences the developing stress response system. For example, maternal presence buffers and regulates infants’ hormonal and behavioral responses to threats (Howell et al., 2017). Sensitive mothers tend to have infants who display better self-regulation during stressful events; intrusive mothers tend to have the opposite effect (Enlow et al., 2014). Warm parenting within a predictable stimulating environment with supportive adults and family can help infants develop the self-regulation skills to adapt to adverse contexts (Blair, 2010). Unfortunately, trauma often disrupts the caregiving system, making adaptation quite difficult.

      Cultural Differences in Temperament

      Researchers have observed consistent cultural differences in temperament that are rooted in cultural norms for how individuals are perceived. Japanese mothers, for example, view their infants as interdependent beings who must learn the importance of relationships and connections with others (Rothbaum, Weisz, Pott, Miyake, & Morelli, 2000). North American mothers, on the other hand, view their task as shaping babies into autonomous beings (Kojima, 1986). Whereas Japanese mothers tend to interact with their babies in soothing ways, discouraging strong emotions, North American mothers are active and stimulating (Rothbaum et al., 2000). Differences in temperament result, such that Japanese infants tend to be more passive, less irritable and vocal, and more easily soothed when upset than North American infants (Kojima, 1986; Lewis, Ramsay, & Kawakami, 1993; Rothbaum et al., 2000). Culture influences the behaviors that parents view as desirable and the means that parents use to socialize their infants (Chen & Schmidt, 2015; Kagan, 2013). Culture, therefore, plays a role in how emotional development—in this case, temperament—unfolds.