Chapter 5 OutlinePlease note that much of this information is quoted from the text.I. MOTOR DEVELOPMENT A. The Dynamic Systems View •Historically, researchers assumed that motor milestones in development were the result of an unfolding genetic plan known as maturation. •More recently, it is recognized that motor development is not the consequence of nature or nurture alone. •Dynamic Systems Theory proposed by Esther Thelen seeks to explain how motor behaviors are assembled for perceiving and acting. •In order to perform an action, several factors come together: —The development of the nervous system —The body’s physical properties and movement possibilities —The goal (behavior or skill) —The environmental support for the skill •It is essentially a process of adaptation: Infants adjust their motor patterns to fit a new task by exploring and selecting various possible configurations. B. Reflexes •Reflexes are built-in reactions to stimuli; they govern the newborn’s movements, which are automatic and beyond the newborn’s control. •Reflexes allow the infant to adapt to its environment. •Rooting reflex: When the infant’s cheek is stroked or side of the mouth is touched, the infant turns its head toward the side that is being touched. This also associated with nursing. •Sucking reflex: Newborns suck on anything placed in their mouth and is adaptive for feeding. Most babies engage in nonnutritive sucking until about 1 year of age. Thumb- sucking is considered a normal activity in infants and young children. •Moro reflex: The newborn arches its back, flings out its arms and legs, and then returns them in an embrace-like movement when startled or perceives a feeling of falling. It is thought to be an evolutionary vestige and disappears at 3 to 4 months. •Grasping reflex: When something touches the infant’s palm, the infant responds by grasping tightly. By the third month, the reflex diminishes and the infant shows a more voluntary reflex. •Some reflexes like coughing, blinking, and yawning persist throughout life. C. Gross Motor Skills Gross motor skills involve large muscle activities, such as moving one’s arms and walking. Infants must be able to maintain their posture (e.g., control heads, strength and balance in their legs) before they can demonstrate gross motor skills. 1. The Development of Posture •Gross motor skills require, at its foundation, postural control. •Posture is a dynamic process that is linked with sensory information from proprioceptive cues in the skin, joints, and muscles, which tell us where we are in space via our vestibular organs, vision, and hearing. 2. Learning to Walk • Locomotion and postural control are closely linked, especially in walking upright. • The neural pathways that control leg alternation are present at birth, or even
prenatally. •The key skills in learning to walk appear to be stabilizing balance on one leg long enough to swing the other forward and shifting weight without falling. •Infants typically take small steps when learning to walk; however, new research indicates that they occasionally take large steps indicative of increased strength and balance. • Newly walking infants are unable to judge the safety of slopes. •Experienced walkers perceptually assess situations—looking, swaying, touching, and thinking before they move down slopes. • Parents should realize how accident-prone children are early in locomotion.3. The First Year: Milestones and Variations •The accomplishment of gross motor milestones can vary by as much as 2 to 4 months; however, the sequence of accomplishments remains fairly stable. By the first month, infants can life their head from a prone position. At about 3 months, infants can hold their chest up and use their arms for support. At 3 to 4 months, infants can roll over. At 4 to 5 months, infants can support some weight on their legs. By 6 months, infants can sit without support. By 7 to 8 months, infants can crawl and stand without support. At 8 months, infants can pull themselves up to a standing position. At 10 to 11 months, they can walk using furniture for support. By 12 to 13 months, they can walk without assistance.4. Development in the Second Year •The motor accomplishments of the first year bring increasing independence. •Child development experts believe that motor activity during the second year is vital to the child’s competent development and that few restrictions, except for safety, should be placed on their adventures. •Pediatricians are cautious of infant/toddler exercise classes. It is easy to stretch an infant/toddler beyond their physical limits without knowing it and the bodies of babies are not ready to benefit from aerobic exercise. • Although it was once believed that walking was a function of maturation, it is now known that practice in the environment is important in learning how to walk. • During the second year, toddlers become more mobile and independent. Experts believe that it is vital to the child’s competent development and that few restrictions, except for safety purposes, should be placed on their motoric adventures. •Structured and/or aerobic exercises are generally not appropriate for babies, and having their limbs stretched by someone else often leads to damage to the infant or toddler. •Cultural variations influence motor development. •Contexts in Life-Span Development: Cultural Variations in Guiding Infants’ Motor Development •Mothers in developing countries tend to stimulate their infants’ motor skills more than mothers in more developed countries. •When caregivers provide babies with physical guidance or opportunities to exercise, infants tend to reach motor milestones earlier than infants not provided these experiences.
•Nonetheless, even when infants’ motor activity is restricted, many infants still reach the milestones of motor development at a normal age. 5. Childhood •Hopping, jumping, running back and forth, and other simple movements are common in 3- and 4-year-olds, but by age 5, they are able to run races and climb easily. •Research indicates that children who are more physically fit have better mastery of motor skills. •Coordination and control of movement improves during middle and late childhood. •Running, climbing, skipping rope, swimming, bicycle riding, and skating are just a few of the many physical skills elementary school children can master. •Boys usually outperform girls in gross motor skill activities. •Children benefit from exercise breaks periodically during the school day on the order of 15 minutes every two hours. •Participation in sports can be positive but may also have negative consequences for children because of pressure to win, physical injuries, distraction from academic work, and unrealistic expectations for success as an athlete. •Applications in Life-Span Development: Parents and Children’s Sports •It is important for parents to show an interest in their children’s sports participation. •If children request that their parents not watch them perform, parents should respect their children’s wishes. •Parents should compliment their children for their sports performance. •If parents do not become over-involved, they can help their children build their physical skills and help them emotionally. •Parents should monitor their children for stress. •Parents need to be sensitive to whether the sport in which the child is participating is the best one for the child. 3. Adolescence and Adulthood •Gross motor skills typically improve during adolescence. •Physical performance peaks between 19 and 26 years of age, including athletes. •The effects of aging eventually result in declines in biological functions (occurs after 30 years of age) and motor skills even in active, biologically healthy individuals. •In general, older adults show a clear slowing of movement with less flexibility. •Physical activity can have positive effects on motor skills in older adults. •Mobility gains are linked to physical activity in older adults. •Lower levels of adiposity are linked to higher levels of physical activity in older adults.D. Fine Motor Skills Fine motor skills involve movements that are more finely tuned than gross motor skills, and several milestones are achieved in infancy (grasping, wrist movements, thumb-finger coordination, etc.). 1. Infancy •Clifton et al. found that proprioceptive cues (muscle, tendon, joint sense), not sight of the reaching limb, guide early reaching for 4-month-old infants. •Infants initially use the palmer grasp, then later develop the pincer grip. •Experience appears to facilitate fine motor skill development.
2. Childhood and Adolescence •Fine motor coordination becomes more precise around age 4. •By age 10 to 12, children begin to show adultlike manipulative skills. •Increased myelination of the central nervous system is reflected in the improvement of fine motor skills during middle and late childhood. •Girls usually outperform boys in fine motor skills. 3. Adult Development • As dexterity decreases in middle and late adulthood, some fine motor skills may decline. • There are two explanations for the decrease in motor behavior in older adults: • Neural noise (an increase in any irregular neural activity) • Strategy • Practice and training programs can minimize the declines in motor function that occur with age.II. SENSORY AND PERCEPTUAL DEVELOPMENT A. What Are Sensation and Perception? •Sensation occurs when information interacts with sensory receptors (eyes, ears, tongue, nostrils, and skin). •Perception is the interpretation of what is sensed. B. The Ecological View •Perception functions to bring the organism in contact with the environment and increase adaptation. •All objects have affordances, which are opportunities for interaction offered by objects that are necessary for performing functional activities. •Research in Life-Span Development: Studying the Newborn’s Perception •After years of work, scientists have developed research methods and tools sophisticated enough to examine the subtle abilities of infants and to interpret their complex actions. •The visual preference method is one way of studying whether infants can distinguish one stimulus from another by measuring the length of time they attend to different stimuli. •The habituation/dishabituation method is another method used to study an infant’s ability to distinguish between stimuli. •The high-amplitude sucking method is used to test an infant’s ability to distinguish auditory stimuli. •Other methods to study infant perception include the orienting response, tracking, and the startle response. C. Visual Perception 1. Infancy a. Visual Acuity •Newborn’s vision is estimated to be 20/240. •By 6 months, average vision is 20/40. •Robert Fantz’s pioneering study of visual perception found that infants look at different things for different lengths of time. Infants prefer patterns to solid colors. b. Color Vision By 8 weeks, and possibly by even 4 weeks, infants can discriminate some colors. By 4 months of age, they have color preferences that mirror adults. Changes in vision reflect maturation and experience.
Early experience is also essential for the normal development of binocular vision, which develops at about 3 to 4 months of age. c. Perceptual Constancy—sensory stimulation is changing but perception of the physical world remains constant. Infants as young as 3 months of age have size constancy (the recognition that objects maintain their size despite a change in the objects’ retinal image), but it continues to develop until 10 or 11 years of age. Infants as young as 3 months have shape constancy (recognition that objects maintain their shape although their orientation to us may change), but not for irregularly shaped objects. Perceptual constancy is important; otherwise infants would think they were seeing different objects every time they saw an object at a different distance or in a different orientation. d. Depth Perception •Gibson and Walk demonstrated, through the use of the visual cliff, to test at what age depth perception develops. •Is depth perception innate? Two- to 4-month-old infants’ heart rate changes when they are placed directly on the deep side of the visual cliff instead of the shallow side. •Most 6- to 12-month-old infants avoided crawling across the cliff. •Stereoacuity (fine-detail depth perception) develops rapidly after 1 year of age. e. Nature, Nurture, and the Development of Infants’ Visual Perception •Vision develops from innate foundations and that the basic foundation of many visual abilities can be detected at birth while others unfold maturationally. Environmental experiences likely refine or calibrate many visual functions, and they may be the driving force behind some functions.2. Childhood Children become better at detecting different hues/colors around 3–4 years. Many preschool children are farsighted, but most can focus and sustain attention on close up objects by first grade. Behaviors that may indicate vision problems include rubbing the eyes, excessive blinking, squinting, appearing irritable when playing games that require distance vision, shutting or covering one eye, and tilting the head or thrusting it forward to look at something. Visual expectations continue to develop in early childhood.3. Adulthood a. Visual Acuity •Accommodation of the eye is the ability to focus and maintain an image on the retina, which declines between age 40 to 59 for most people. Middle-aged people have difficulty viewing close objects and often find their sight improved with bifocal lens glasses. •This loss of accommodation is known as presbyopia. •The eye’s blood supply diminishes in the 50s or 60s. •The blind spot increases, possibly due to the reduced blood supply. •The retina may become less sensitive to low levels of illumination in middle adulthood. •Night driving becomes more difficult because of a declining dark adaptation and glare adaptation in late adulthood. •In extreme old age the declines in sight may be accompanied by degenerative changes in the retina.
•Older adults show a decline in motion sensitivity. b. Color Vision •Yellowing of the lens in older adulthood can limit color vision. c. Depth Perception Depth perception declines in late adulthood, at least partially because of a decrease in contrast sensitivity. d. Diseases of the Eye •Cataracts—a thickening of the lens of the eye that causes vision to become cloudy, opaque, and distorted is more common in older adults. These can be repaired surgically. •Glaucoma—a buildup of fluid in the eye because of damage to the optic nerve —is also more common in older adults and is treated with eye drops. If left untreated, it can destroy vision totally. •Macular degeneration is a disease involving deterioration of the retina and is linked to aging. Because it is difficult to treat, it is a leading cause of blindness in older adults. If detected early, it can be treated with laser surgery.D. Hearing 1. The Fetus, Infant, and Child •DeCasper and Spence’s research showed that fetuses can hear a couple of months before birth. Two important conclusions from DeCasper and Spence’s research are that: —Ingenious scientists can assess the development of fetuses. —Infants’ brains have the ability to learn even before birth. •Immediately after birth, newborns can hear (their sensory threshold is higher than adults). •Newborns prefer human speech to other sounds and prefer their mother’s voice to that of other, unfamiliar women. •Changes in hearing during infancy are seen in loudness, pitch, and localization. •About 1 in 1,000 newborns are deaf, so screening is important. •Many of the hearing impaired children who have early cochlear implant surgery show good progress with their speech and understanding others’ speech. •Chronic otitis media can impair language development and socialization. 2. Adolescence •Hearing in adolescence is usually excellent, but there is special concern for those who listen to loud music for long periods of time. •Listening to music at high levels on iPods and MP3 players may contribute to hearing problems in youth. •Adolescents are generally aware of the risks of loud music exposure, but express low personal vulnerability to such experiences. 3. Adulthood •Declines begin at around age 40, with sensitivity to high-pitched sound declining first. •Hearing is not functionally impaired in most people until later adulthood and is usually due to degeneration of the cochlea. •Wearing hearing aids or cochlear implants can restore some hearing. •Use of adult stem cells is being researched as an alternative to cochlear implants. •Declines in hearing are much greater in adults 75 years of age and older than those under 75. •There is a significant deterioration in hearing sensitivity across the eighties,
although older adults may not perceive the change. •Older women are more likely to seek treatment for their hearing problems than are older men. •Hearing loss in older adults is linked to increased depression, less activities, and less participation in social roles. E. Other Senses 1. Touch and Pain A. Infancy •Newborns respond to touch. •It was once thought that newborns are indifferent to pain; however, research on male circumcision demonstrates that newborns are sensitive to pain. 2. Adulthood •Some decline in touch sensitivity has been found in the lower extremities, although this is not problematic for most people. •As we age, we become less sensitive to pain, which is helpful for coping with disease and injury but can be harmful if it masks the signs of injury that need to be treated. 3. Smell •Newborns can differentiate odors. •Using facial expressions as an indicator, researchers infer that newborns prefer vanilla and strawberry smells, but do not like rotten egg or fish smells. •By 6 days (but not by 2 days), breast-fed babies prefer the smell of their mother’s breast pad, indicating that this preference requires several days of experience to recognize the odor. •A decline to sensitivity to odors may occur as early as the 20s and continues to decline through each subsequent decade of life. •Beginning in the 60s, the decrease in sensitivity to smells becomes more noticeable to most people aged 60. •The decline in the olfactory system can reduce older adults’ enjoyment of food, life satisfaction, and ability to detect smoke from a fire. •A recent study found that although adults’ ability to detect a smell declined as they got older, the perceived pleasantness of a smell increased in the oldest adults. 4. Taste •Taste sensitivity is present prior to birth. •When saccharin was added to amniotic fluid, fetal swallowing increased. •By 2 hours old, babies make different facial expressions when they taste sweet, sour, and bitter solutions. •Declines in taste often begin to occur in the 60s and, combined with the lowered sense of smell, can affect eating behavior. F. Intermodal Perception •Intermodal perception is the ability to relate and integrate information about two or more sensory modalities. •Infants as young as 3½ months of age can connect visual and auditory stimuli, although newborns may have a crude intermodal perceptual ability. •Newborns are born into the world with some innate abilities to perceive relations among sensory modalities, but their intermodal abilities improve considerably through experience.III. PERCEPTUAL-MOTOR COUPLING
•It was once believed that perceptual and motor development were isolated from each other.•Increasingly, it is believed that perceptual-motor development is coupled and unified.•Babies are continually coordinating their movements with concurrent perceptual informationto learn how to maintain balance, reach for objects, and locomote across various surfaces.•Declines in perceptual-motor skills in older adulthood can reduce the ability to drive.