Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 249

Motor milestones, such as the ability to crawl, might look like isolated achievements, but they actually develop systematically and build on each other with each new skill preparing an infant to tackle the next (Thelen, 1995, 2000). According to dynamic systems theory (see Chapter 1), motor development reflects an interaction among developmental domains, maturation, and environment (Thelen, 1995, 2000). Simple motor skills are combined in increasingly complex ways, permitting advances in movement, including a wider range and more precise movements that enable babies to more effectively explore and control their environments. Separate abilities are blended together to provide more complex and effective ways of exploring and controlling the environment. For example, the abilities to sit upright, hold the head upright, match motor movements to vision, reach out an arm, and grasp are all combined into coordinated reaching movements to obtain a desired object (Corbetta & Snapp-Childs, 2009; Spencer et al., 2000). Motor skills become more specialized, coordinated, and precise with practice, permitting infants to reach for an object with one hand without needlessly flailing the other, for example (D’Souza, Cowie, Karmiloff-Smith, & Bremner, 2017).

Motor skills also reflect the interaction of multiple domains of development. All movement relies on the coordination of our senses and cognitive abilities to plan and predict actions. Sensory abilities such as binocular vision and the ability to direct gaze combine with exploratory hand and foot movements, designed to determine the opportunities a given surface provides for movement. For example, when 14-month-old infants were tested on a “bridge” of varying widths, they explored the bridge first with quick glances (Kretch & Adolph, 2017). When faced with an impossibly narrow width, infants with walking experience tended to engage in more extensive and time-consuming perceptual and motor exploration, such as touching with hands and feet, to determine whether to cross the bridge.

Motor development reflects goal-oriented behavior because it is initiated by the infant or child’s desire to accomplish something, such as picking up a toy or moving to the other side of the room. Infants’ abilities and their immediate environments (e.g., whether they are being held, lying in a crib, or lying freely on the floor) determine whether and how the goal can be achieved (Spencer et al., 2000). The infant tries out behaviors and persists at those that enable him or her to move closer to the goal, practicing and refining the behavior. For example, infants learn to walk by taking many steps and making many falls, but they persist even though, at the time, crawling is a much faster and more efficient means of transportation (Adolph et al., 2012). Why? Perhaps because upright posture leads to many more interesting sights, objects, and interactions. The upright infant can see more and do more, with two hands free to grasp objects, making walking a very desirable goal (Adolph & Tamis-LeMonda, 2014). New motor skills provide new possibilities for exploration of the environment and new interactions with caregivers that influence opportunities. Differences in caregiver interactions and caregiving environments affect children’s motor skills, the form they take, the ages of onset, and the overall developmental trend (Adolph & Franchak, 2017).

Social and cultural influences provide context to our movements. Motor skills do not develop in isolation; rather, they are influenced by the physical and social context in which they occur. For example, a naturalistic study of video records of at-home interactions of mother–infant pairs from six countries revealed large differences 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 or 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 run 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 because 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.