Sensation and Perception During Infancy and ToddlerhoodMethods for Studying Infant PerceptionVisionFace PerceptionObject ExplorationColor VisionDepth PerceptionHearingTouchSmell and TasteIntermodal PerceptionInfant–Context Interactions and Perceptual Development
Motor Development During Infancy and ToddlerhoodGross Motor DevelopmentFine Motor DevelopmentBiological and Contextual Determinants of Motor DevelopmentBiological Influences on Motor DevelopmentContextual Influences on Motor DevelopmentMotor Development as a Dynamic System
Body Growth
Perhaps the most obvious change that infants undergo during the first year of life is very rapid growth.
Growth Trends
It is easy to observe that infants grow substantially larger and heavier over time—but there are many individual differences in growth. How can parents and caregivers tell if a child’s growth is normal? By compiling information about the height and weight of large samples of children from diverse populations, researchers have determined that growth follows distinct patterns. Growth norms are expectations for typical gains and variations in height and weight for children based on their chronological age and ethnic background.
In the first few days after birth, newborns shed excess fluid and typically lose 5% to 10% of their body weight. After this initial loss, however, infants gain weight quickly. Infants typically double their birthweight at about 4 months of age, triple it by 12 months, and quadruple it by 2.5 years (Kliegman et al., 2016). The average 3-year-old weighs about 31 pounds. Gains in height of 10 to 12 inches can be expected over the first year of life, making the average 1-year-old child about 30 inches tall. Most children grow about 5 inches during their second year of life and 3 to 4 inches during their third. To parents, growth may appear slow and steady, but research has shown that it tends to occur in spurts in which an infant or toddler can grow up to one-quarter of an inch overnight (Lampl et al., 2001). Infant growth appears to be tied to sleep, as increased bouts of sleep predict small bursts of growth (Lampl & Johnson, 2011). At about 2 years of age, both girls and boys have reached one-half of their adult height (Kliegman et al., 2016).
Patterns of Growth
Over the course of infancy, children get larger and heavier, but growth is uneven. Different parts of the body grow at different rates. Growth during the prenatal period and infancy proceeds in two systematic patterns. Cephalocaudal development refers to the principle that growth proceeds from the head downward. The head and upper regions of the body develop before the lower regions. For example, recall the fetus’s disproportionately large head. During prenatal development, the head grows before the other body parts. Even at birth, the newborn’s head is about one-fourth the total body length, as shown in Figure 4.1. As the lower parts of the body develop, the head becomes more proportionate to the body. By 3 years of age, the child is less top-heavy. Proximodistal development refers to the principle that growth and development proceed from the center of the body outward (Figure 4.2). During prenatal development, the internal organs develop before the arms and legs. After birth, the trunk grows ahead of the arms and legs, and the arms and legs tend to grow ahead of the hands and feet.
Figure 4.1 Body Proportions Throughout Life
Source: Huelke (1998).
Figure 4.2 Cephalocaudal and Proximodistal Development
Growth is largely maturational, but it can be influenced by health and environmental factors. Today’s children grow taller and faster than ever before, and the average adult is taller today than a century ago. Increases in children’s growth over the past century are influenced by contextual changes such as improved sanitation, nutrition, and access to medical care (Mummert, Schoen, & Lampl, 2018). Large gains have occurred in North America and Europe, followed by South Asia (NCD Risk Factor Collaboration, 2016). Although children of sub-Saharan Africa showed growth gains into the mid-1990s, mass poverty and starvation, poor infrastructure to provide clean water and sanitation, and exposure to the emotional and physical stresses of war and terror have affected growth (Simmons, 2015). Contextual factors can both help and harm children’s development.
Nutrition and Growth
Good nutrition is essential to healthy growth during infancy and toddlerhood. Many infants’ first nutritional experiences are through breast milk.
Breastfeeding
The U.S. Department of Health and Human Services (2011) has recommended that mothers breastfeed their babies, and breastfeeding has increased in popularity in the United States in recent years. In 1990, about one-half of mothers breastfed their babies, whereas about 83% breastfed in 2014 (Centers for Disease Control and Prevention, 2017b). Over one-half of women continue to breastfeed after 6 months and over one-third at 12 months.
Breastfeeding practices vary by maternal age, education, and socioeconomic status (Hauck, Fenwick, Dhaliwal, & Butt, 2011). In the United States and the United Kingdom, for example, the lowest rates of breastfeeding are among low-income mothers, mothers who are young, and mothers with low levels of education. Researchers have observed that the employment settings of low-income mothers may offer few resources to support breastfeeding, such as private places for women to use breast pumps (Griffiths, Tate, & Lucy, 2007; Racine, Frick, Guthrie, & Strobino, 2009). In contrast, women in developing countries who have low educational levels and are in the poorest social classes are more likely to breastfeed their children. Educated women of higher income brackets in these countries tend to shun breastfeeding, viewing it as an option primarily for poor women (Victora et al., 2016). Other factors affecting breastfeeding practices include ethnicity and social policies. In the United States, for instance, Hispanic mothers breastfeed at higher rates than non-Hispanic White mothers, who are more likely to breastfeed than non-Hispanic Black mothers (Centers for Disease Control and Prevention, 2013; Smith-Gagen, Hollen, Walker, Cook, & Yang, 2014). And unsurprisingly, countries where working women are allowed paid maternity leave for part or all of their infant’s first year of life, such as Denmark, Norway, Sweden, and Australia, show very high breastfeeding rates of 94% and more (Hauck et al., 2011; Imdad, Yakoob, & Bhutta, 2011; Roelants, Hauspie, & Hoppenbrouwers, 2010).
Breastfeeding is associated with many health benefits for infants and mothers and provides opportunities for infant–mother bonding.
©iStockphoto.com/kate_sept2004
Breastfeeding offers benefits for mothers and infants. Mothers who breastfeed have lower rates of diabetes, cardiovascular disease, and depression, and after they reach menopause, they are at lower risk for ovarian and breast cancer and bone fractures (Godfrey & Lawrence, 2010; Islami et al., 2015). A mother’s milk is tailored to her infant and has the right amount of fat, sugar, water, and protein needed for the baby’s growth and development. Most babies find it easier to digest breast milk than formula. In addition, breast milk contains immunizing agents that protect the infant against infections, and breastfed infants tend to experience lower rates of allergies and gastrointestinal symptoms as well as have fewer visits to physicians (Cabinian et al., 2016; Turfkruyer & Verhasselt, 2015). Breastfeeding for more than 6 months is associated with reduced risk of obesity and childhood cancer, especially lymphomas (Amitay, Dubnov Raz, & Keinan-Boker, 2016; Victora et al., 2016). Recent research suggests that exclusively breastfeeding during the first 4 to 6 weeks of life may be associated