Lifespan Development. Tara L. Kuther

in opportunities for infant sitting and infant performance (Karasik, Tamis-LeMonda, Adolph, & Bornstein, 2015). Infants from the United States, Argentina, South Korea, and Italy spent most of their sitting time in places that offered postural support, such as child furniture. In contrast, infants from Kenya and Cameroon, who spent most of their sitting time in places that offered little postural support, such as the ground of adult furniture, tended to show the longest bouts of independent sitting and at the earliest age. Cultural differences in daily activities influence motor skills across the lifespan. Long-distance running is part of daily life for Tarahumaran children, who routinely run 10 to 40 kilometers in a few hours and adults 150 to 300 kilometers in 24 to 48 hours (Adolph & Franchak, 2017). From childhood, East African females carry heavy loads balanced on their heads, altering their posture and gait to complete a contextually important activity.

      Therefore, from a dynamic systems perspective, motor development is the result of several processes: central nervous system maturation, the infant’s physical capacities, environmental supports, and the infant’s desire to explore the world. It is learned by revising and combining abilities and skills to fit the infant’s goals. In this way, motor development is highly individualized as each infant has goals and opportunities that are particular to his or her specific environment (Adolph & Franchak, 2017). For example, an infant might respond to slippery hardwood floors by crawling on her stomach rather than all fours or by shuffling her feet and hands rather than raising each. Infants attain the same motor tasks, such as climbing down stairs, at about the same age, yet differ in how they approach the task. Some, for example, might turn around and back down, others descend on their bottoms, and others slide down face first (Berger, Theuring, & Adolph, 2007). By viewing motor development as dynamic systems of action produced by an infant’s abilities, goal-directed behavior, and environmental supports and opportunities, we can account for the individual differences that we see in motor development.

      Thinking in Context 4.5

      1 Carmen is concerned because her 14-month-old baby is not walking. All of the other babies she knows have walked by 12 months of age. What would you tell Carmen?

      2 How might a fine motor skill, such as learning to use a spoon, reflect the interaction of maturation and sociocultural context?

      Apply Your Knowledge

      Lena is 7 months old and lags behind in height and weight compared with other infants her age. Early in life, she showed normative growth, but her growth has since slowed. Recently, Lena’s parents separated, and she and her mother moved to a new home. Her mother is 19 years old, does not have a high school degree, and had few job opportunities. She took the first job that panned out, despite its long hours. Lena was placed in child care. Her mother continued to breastfeed, despite its increasing difficulty given her new work schedule. Lena’s mother insisted that Lena eat less solid food and baby food given her continued breastfeeding. Staff at the child care center approached Lena’s mother to express their concern over Lena’s lack of growth and development; she has not begun crawling like other infants and tends to avoid eye contact with others.

      1 What are normative patterns of growth for infants? Motor skills? How does Lena’s development compare with these norms?

      2 .What are potential causes of or influences on the developmental difficulties Lena experiences? How might contextual factors influence Lena’s development?

      3 What are the child care staff’s responsibilities?

      4 What should the mother do? What treatment do you suggest?

      Descriptions of Images and Figures

      Back to Figure

      As a newborn, the head is one fourth of the whole body. At 2 years, the head is slightly smaller in relation to the body. At 6 years, the head is about one fifth of the body. At 12 years, the head is a little more than one fifth of the body. At 25 years, the head is one sixth of the body.

      Back to Figure

      The outermost layer of the brain is the cerebral cortex. It is composed of folded gray matter and is divided into four lobes: (1) the frontal lobe, located at the front of the brain; (2) the parietal lobe, located in the middle section of the brain; (3) the temporal lobe, located in the bottom section of the brain; and (4) the occipital lobe, located at the back of the brain.

      Key structures noted on the illustration include the corpus callosum, found in the middle section of the brain, and the thalamus, hypothalamus, amygdala, and hippocampus, located near the base of the brain. At the back of the brain is the cerebellum.

      Back to Figure

      Set 1: pair of stars.

      1-month-old: The bottom-most portion of the star has been marked heavily with a pen or marker.

      2-month-old: Most of the shape has been marked heavily with a pen or a marker, with only a few of the other edges still visible.

      Set 2: pair of faces.

      1-month-old: It is noted that infants first look at the chin, scan up toward the eyes, and then scan toward the top of the head. There is some back-and-forth scanning between the eyes and top of head. Infants tend to finish scanning at the top of the head.

      2-month-old: It is noted that infants first look toward the top of the person’s head. They then move to the eyes and frequently scan back and forth between the eyes, mouth, and top of head. At the end of their visual scanning, they are typically focused on the eyes.

      Back to Figure

      The illustration shows a glass box with a checker pattern on half of the top pane of glass. The other side of the box has a checker pattern on the bottom, creating the illusion of a cliff. An infant is placed on top of the top checker pattern. An adult stands on the opposite side, calling for the baby. The baby would have to cross the portion of the top pane of glass with no checker pattern to reach the adult.

      Next to this illustration is a photo of a crawling baby on such a visual cliff apparatus. The baby is on the patterned part of the box, and an adult calls to the baby.

      Back to Figure

      Rates are highest in the Midwest, followed by the Northeast, South, and then West. Rates in 1979 ranged from 55% to about 75% for all four regions. By 2010, however, rates were notably lower in the West, averaging about 40% compared with 56% to 67% in the other three regions.

      Approximate rates by year are listed for each region.

       Midwest:

      1979: 75%

      1985: 70%

      1990: 75%

      1995: 80%

      2000: 80%

      2005: 78%

      2010: 70%

       Northeast:

      1979: 65%

      1985: 65%

      1990: 63%

      1995: 68%

      2000: 65%

      2005: 67%

      2010: 66%

       South:

      1979: 55%

      1985: 55%

      1990: 57%

      1995: 66%

      2000: 65%

      2005: 60%

      2010: 59%

       West:

      1979: 65%

      1985: