Infancy is the period from birth to age 2. This chapter will explore trends in infant physical and motor growth and examine the growth of the infant brain.

1. Physical growth and motor development

1. Infants grow very rapidly between birth and age 2.
2. By the second year, although they remain top-heavy, their legs and trunk grow rapidly and begin to catch up with the rest of the body.
3. A layer of subcutaneous fat, commonly called "baby fat", gives the young baby a plump appearance.
4. By age 2 toddlers have lost some of this subcutaneous fat and with it, their roundish appearance.
5. During infancy, muscle and bone tissue grows rapidly, explaining the remarkable increase in strength, coordination, and stamina that occurs during this period.
6. A brain growth spurt also takes place, causing babies to gain physical competence by leaps and bounds.
7. Motor Abilities:

1. Motor abilities emerge in a relatively fixed order
2. Babies creep before they walk.
3. They swipe at objects before they can accurately reach out and grab them
4. They grasp objects by trapping them between their fingers and palm before using the thumb and index finger in a more sophisticated pincer grasp
5. Early child development researchers have studied the emergence of these infant motor behaviors and have created developmental charts-called normative charts-that show the average age at which certain behaviors first appear
6. Although the sequence of motor development is relatively fixed, not all children acquire motor abilities at the same pace
7. Cultural and individual differences in motor development may be explained by a result of biological inheritance
8. Research exists to support this claim
9. In a study of Hopi Indian infants, those who had been tightly swaddled and strapped to a cradleboard walked at about the same age as those who were not confined in this way
10. Researchers have concluded that babies will ultimately follow their own unique maturation patterns regardless of environmental influences
11. Cultural variations in development may be the result of a unique blend of parenting values and practices, family life, and genetic contributions from ancestors

8. Toddler motor development and self-help skills:

1. During the last half-year of infancy-from approximately age 18 months to 2 years-children enter a new period of development called toddlerhood
2. Changes in intellectual, language, and motor growth mark this as an especially challenging and fascination period
3. Toddlers cut most of their teeth between 18 months and 2 years
4. In toddlerhood, fine motor abilities that require the coordination of fingers and thumb are acquired
5. Child-proofing is especially important in toddlerhood, as choking is a major concern at this age

9. Child-proofing from a multicultural perspective:

1. Child-proofing takes many forms and is influenced by cultural values and practices.
2. In some families, home environments are fully redesigned during toddlerhood so that babies can touch anything they wish; the goal is to encourage autonomy and reduce reprimands and restrictions
3. In other families, toddlers are required to learn rules for what may be touched or played; infractions are met with hand-slapping or firm reprimands
4. As children become more advanced motorically, they are expected to perform certain self-help tasks; which tasks are to be learned and how quickly children are expected to learn them are defined by particular cultures

10. Eating:

1. Eating with a toddler is an experience in any culture
2. In some families, toddlers are expected to sit for meals and eat with a spoon or another eating implement as early as age 2
3. Variation in how toddlers eat is a function of the foods eaten in a particular culture and the implements used

11. Toileting:

1. Toddlerhood is often a time when American parents decide to train their children to use the toilet independently.
2. In the US, parents take many different approaches to toilet training,
3. White middle-class parents often adhere to a "child-oriented approach" suggested by baby experts
4. In this method, parents wait until they are absolutely certain the child is ready, then use gentle reminders, modeling, and positive guidance to help children achieve independent toileting
5. Some middle-class American parents have adopted behaviorist strategies in which rewards and praise are used to shape independent toileting behaviors
6. After extensive observations in many non-Western countries, J.W.M Whiting reported that toileting was seldom mentioned by parents in discussions of child-rearing issues
7. In a classic study of toileting practices in East Africa, babies at 3 weeks old are taken to a special place outdoors to urinate or defecate; this occurs night and day; at the phenomenally early age of 5 months, many babies of this community begin to communicate a need for elimination with noises or body movements
8. Regardless of whether harsh reprimands, rewards, or modeling is used, or even when no conscious effort to train is made at all, most children achieve bladder and bowel control by age 3

2. Perceptual Development

1. Long ago it was believed that babies were born into a confusing world of fuzzy shapes and strange, garbled sounds
2. Most thought only older infants could see faces, recognize voices, or distinguish among tastes and smells
3. New techniques have shown babies have remarkable perceptual abilities right after birth
4. Vision:

1. Newborns see quite well objects that are between 7 and 15 inches away; this is approximately the distance a parent's face is from an infant who is being held
2. Babies' visual acuity increases over the first few months of life; it is estimated that by age 1, they see as well as they ever will
3. One way we know that young babies can see clearly is that they like to look at some patterns or objects more than others
4. Newborns prefer patterns over solid shapes curved lines over straight ones, and large squares over small ones
5. By 4 months, babies can also distinguish among colors and prefer blue and red to yellow-the same color preferences as adults
6. One thing that newborn babies may prefer to look at are human faces
7. Newborns' innate visual interests, present at birth, may promote parent bonding
8. Tracking and scanning are two special abilities that assist babies in viewing the world
9. Tracking is the ability to visually follow a moving object with one's eyes
10. Newborn babies only follow objects moving side-to-side in their field of vision
11. Tracking becomes smoother and more accurate during the first 6 months of life
12. Scanning is a visual ability to look over all the features of an object and get a complete picture of what it is like
13. Newborns tend to look at only one feature of a stimulus-at just one corner of a triangle or one ear of a teddy bear
14. Within 3 months after birth, babies become much more competent in scanning an entire object
15. They quickly look at one feature and then another until they have processed the whole object
16. Another visual ability of infants is depth perception
17. It has been discovered that babies as young as 6 months would not crawl out over a visual cliff even when they were encouraged to do so by their mothers (The cliff was a safe surface covered with clear glass which only gave the appearance of being a deep abyss)
18. 10- and 12-month-olds were found to have sophisticated distance perception-a form of depth perception
19. They were found to more often reach for objects that were close to them, but less often for those were far away; even newborns only days old have been found to widen their eyes, pull back their heads, and hold up their hands when they view objects moving toward them

5. Hearing:

1. Babies can hear quite well, perhaps even before birth
2. Fetuses as early as 26 weeks after conception were found to respond to sounds with accelerated heart rates and increased movement
3. Newborns can distinguish among sounds of different kinds-high and low pitches or loud and soft noises
4. Certain sounds, such as lullabies, singing, or heartbeats, tend to soothe them
5. Others, such as sudden, high pitched noises, agitate them

6. Newborns tend to cry at the sound of other infants' crying
7. Humans may be born with an innate propensity to become upset over human cries
8. Babies are more attentive to certain sounds
9. They prefer singing and women's voices and they are especially attentive to the voice of their own mother
10. They can discriminate among individual consonant sounds, even those of other languages
11. Babies as young as 2 days old can distinguish adult-to-child speech (which is characterized by especially exaggerated, higher-pitched intonation) from adult-to-adult speech
12. Five-month-olds are able to discriminate between intonations indicating approval and disapproval even when uttered in different languages
13. Abilities to locate the direction of sounds, search for and track their sources, and selectively listen to one sound over another are acquired as early as 5 months

6. Taste and Smell:

1. Taste and smell develop early among the senses
2. The ability to discriminate among smells and tastes may be acquired well before birth
3. Newborns can distinguish among five tastes: sour, bitter, salty, sweet, and neutral
4. They have clear taste preferences
5. Newborns do not appear to like salty solutions
6. The craving for salty snacks prevalent in some American cultures may be an acquired taste
7. Newborns can distinguish between pleasant and unpleasant smells
8. They also can detect where an odor is coming from; when an unpleasant smell comes from one direction, they rapidly turn their heads the opposite way
9. Taste and smell are critical for neonatal survival
10. Infant preferences for certain sweetish, nonsalty solutions will facilitate early nursing
11. Babies only a few days old prefer the odor of their own nursing mothers' breast pads to the smells of those of unfamiliar lactating women
12. These odor preferences do not exist among bottle-fed babies; this suggests that such preferences arise from early experience with maternal smells
13. Female babies are more likely to show these preferences than are males, suggesting a genetic cause

7. Touch:

1. The sense of touch develops before birth and plays a critical function in human development throughout life
2. Parental touch has a positive effect on infant emotions and health
3. Babies are soothed by being stroked or patted
4. Parental touching has been found to elicit smiles, gazes, and increased attention to positive developmental outcomes for at-risk babies
5. Touch also serves as a medium for learning about things
6. Newborns can distinguish among tactile stimuli and discriminate between touches to one part of the body or another
7. Touch is often used in conjunction with other senses to interpret the world
8. For example, looking and touching may be utilized together to recognize a toy

3. Perceptual-motor challenges in infancy

1. Some disabilities are detected early in infancy or even before birth; their full impact on babies' ability to move about and explore objects and people may not be fully realized until the middle of the first year
2. Visual impairment:

1. Babies with visual impairment but with no other disabilities will develop early motor skills at a typical pace
2. At a point when sighted infants begin to reach for and grasp objects, blind babies will not
3. At an age when most typically developing babies are beginning to crawl or walk, blind babies remain relatively stationary
4. Blind babies move less because they are not visually inspired to get somewhere
5. They don't reach as often, because they are not motivated to obtain an object which they cannot see
6. Rich auditory experiences must be created for infants with visual impairments
7. Providing toys that have interesting tactile and sound qualities has been found to promote the motor abilities

3. Hearing impairment:

1. This challenging condition may not be obvious in the early weeks of life
2. Babies with poor or no hearing may acquire motor abilities and even babble much like unimpaired infants
3. When they have acquired motor skills that allow them to respond to auditory stimuli their challenging condition becomes obvious
4. The majority of research on hearing disability in infancy focuses on delays in language development
5. Hearing-impaired babies show significant problems in learning language
6. When parents are warm and responsive in their interactions, their hearing-impaired babies become as securely attached as hearing babies
7. Down syndrome can produce motor delays that are observable in infancy
8. Physical malformations resulting from the disorder can also affect perception
9. Eye cataracts, for example, are prevalent in babies with Down syndrome
10. Cerebral palsy, a condition caused by brain damage from oxygen deprivation or trauma before or during birth, often leads to blindness, deafness, or permanent impairment of motor abilities
11. Early intervention can significantly affect the degree to which disabilities interfere with motor development
12. In one study, children with sever motor impairments were provided with intensive services, including home-based intervention, parent support, and social services
13. During the 12 months of the study, infants achieved an 8 to 12 month gain in motor development

4. Brain Growth

1. A baby's brain develops at an astonishing rate; by age 3 it is as complex as it will ever be
2. How the brain works:

1. The brain is comprised of billions of brain cells, called neurons, that are designed to send and retrieve information across organs or muscles
2. Each neuron is made up of a cell body that is surrounded by dendrites, elongated tissues that receive messages
3. A very long thread of tissue, the axon , extends out from the cell body toward other nerve cells
4. The purpose of the axon is to send messages
5. The message in one cell is transmitted to another via chemical secretions called neurotransmitters
6. These travel out of the axon of one cell and pass into the dendrites of the next 
7. The place where the axon and the dendrite meet is called a synapse
8. The number of synapses in the brain increases rapidly during infancy ad accounts for the remarkable intellectual growth during this period
9. Another tissue that helps neural messages to travel efficiently from one cell to another is myelin
10. This is a fatty sheath that surrounds the axon and ensures that signals travel efficiently,, quickly, and accurately
11. The brain is organized into regions
12. Each of these is responsible for specific functions
13. Sensory regions send and receive information regarding the sense organs
14. Motor regions regulate movement
15. Association regions are responsible for complex thought processes
16. One important area of the brain is the frontal cortex, which develops rapidly beginning at around 8 months
17. This area is associated with the ability to express and regulate emotions
18. The brain is also organized into right and left hemispheres
19. In right-handed individuals, the left hemisphere governs analytical thinking and language and the right hemisphere governs spatial and auditory perception
20. The left hemisphere controls the right visual field and the right controls the left visual field
21. This specialization of left and right sides of the brain has been referred to as brain lateralization

 

3. The "super-dense" infant brain

1. The number of neurons and the connections among them-the synapses-increase at a startling rate in the early years
2. By age 2, the number of synapses reaches an adult level
3. By age 3, a child's brain has 1, 000 trillion synapses-twice that of any reader of this textbook
4. Infants brains have been referred to as super-dense
5. They contain more complex neural connections and have a higher metabolic rate than at any other period of life
6. Babies acquire more synapses than they will need
7. So, after age 3 some of these connections are eliminated
8. In the elementary years, as many synapses are lost as are added
9. By adolescence, the loss of synapses far outpaces their acquisition
10. Typical 18-year-olds, have lost roughly half of their infant synapses
11. After infancy, brain growth is a pruning process in which brain connections that are not used or needed disappear
12. Synapses that have not been used often enough disappear, while those that have been reinforced through experience become permanent
13. If babies exercise synapses in the cerebral cortex that are responsible for thinking and language, these will be maintained
14. Babies will become more competent in these areas
15. Children who do not use these synapses may be hampered in language or thinking
16. Brain growth is an interaction between biology and cultural experience

4. Promoting infant brain growth

1. Early stimulation is a key component of promoting infant brain growth
2. Providing perceptual, motor, and language experiences for babies will enhance the formation of dendrites and increase the number of synapses
3. Overstimulation-a constant bombardment of sights and sounds-would work against healthy brain growth

4. Such experiences might cause stress, leading to interference in neural development
5. The most powerful influence on infant brain growth is attachment-the process by which infants bond emotionally with significant adults in their lives
6. When babies receive warm, responsive care from parents and other caregivers, they come to know and trust these adults
7. When babies experience stressful events, levels of a hormone called cortisol are elevated in the body
8. Cortisol threatens brain development by reducing the number of synapses and leaving neurons vulnerable to damage
9. Babies who suffer great trauma-as in the case of child abuse or neglect-are at risk of poor brain growth because of these high cortisol levels
10. In particular, areas of the brain that regulate emotions are affected
11. Infants under great stress are more likely to suffer anxiety, impulsivity, hyperactivity, and poor control of their emotions later in life
12. Babies who are securely attached to caregivers are less likely to produce cortisol under stressful conditions
13. When they do, the levels of this hormone are far lower than those for children who are not attached
14. A warm bond with parents and other caregivers-so important for security and happiness-also has a positive impact on physical brain development

5. "Prime Time" for Brain Growth

1. Since the brain grows so rapidly in infancy, this period is considered a prime time of neural growth
2. This prime time is also a period of great vulnerability
3. Brain development is significantly impaired by in utero exposure to drugs, child abuse, maternal depression, and other factors
4. Early intervention can offset such negative influences if provided in the first 3 years of life

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