Physical and Motor Development of Infants

Physical and Motor Development of Infants Abstract As human beings, we have a gradual and systematic development and this development refers to systematic continuities and changes in the individual that occur between conception and death. In psychology, separate discipline has developed to study the human development called “Developmental Psychology.” Physical and motor development of infants that comes under this discipline is very important as this infant development makes the foundation for other developmental processes. There are many books written on human development specially on infant development and among those books, the book “Child Development” written by Laura Berk, “ Child Psychology” written by Ross. D. Parke and Otis Locke hold a very important place. Here by doing this assignment, our group has tried to summarize the topics on physical and motor development of infants in those books and translate it into Sinhala. Introduction The physical growth of human beings is an extended experience in comparison to most of the other living species. Physical immaturity of humans is a widely examined subject both in developmental psychology and in biology. In fact, physical growth of humans is identified as four different stages naming infancy, childhood, adulthood and old age (Berke, 2000 ). The course of physical growth is studied according to changes in body size, changes in body proportions, changes in muscle-fact make up, skeletal growth, gains in motor skills and hormonal influences. The changes that occur in body size are the most visible trait of physical growth. During prenatal period and mostly during infancy the growth rate is very high. The distance curve and the velocity curve are two types of growth indicators, which are used by developmental psychologists and biologists for analytical purposes. The changes in body proportions are quite clear during prenatal period and adolescence. In the prenatal period, the head of the embryo develops first and the lower parts of the body later. Even though both girls and boys are similar in body amounts during infancy and child hood, adolescence marks significant proportional differences between boys and girls. The action of sex hormones is the cause behind. The level of Muscle-Fat is another crucial factor in physical growth. During the last few weeks of prenatal phase, the level of muscle fat reaches its peak in order to maintain a constant body temperature. This increase and decrease of muscle fat continues displaying various levels of Muscle Strength between boys and girls. The skeletal age is considered as the best estimate of a child’s physical maturity. The production of cartilage cells that gradually harden into bone at the growth plates of the epiphyses is the core of the growth process. According to certain studies, some children tend to be slightly ahead of others in terms of skeletal age. The above three factors directly influence on an explosion of new gross motor skills. As the physical structure becomes reorganized and less top-heavy, the centre of gravity shifts toward the trunk and the resulting improvement leads towards new motor skills involved in large muscles. The advances in motor skills can be identified as a portrayal of changing lower body skills to actions that are more effective. These advancements can never be viewed only as a physical growth; these are the results of developing mental capabilities of the individual. In addition to physical and mental growth, the social expectations that are absorbed by children at an early age influence their performances of motor skills. The social expectancy that girls are less positive than the boys regarding the value of sports and their sports abilities, may affect individual motor skills during adolescence. Thus, the growth should never be measured depending only on physical characteristics. Sports and exercise are highly decisive in developing motor performance (Parke & Locke, 1999). They influence on cognitive and social development too. The manufacturing and secretion of hormones by endocrine glands is a remarkable duty performed by human body in order to support the physical growth. The pituitary gland located at the base of the brain near the hypothalamus releases the most important hormones for physical growth. Growth Hormone, secreted throughout life by the pituitary gland affects the development of all tissues except the central nervous system and the genitals. Growth Hormone production doubles in puberty and decreases after final adult height is reached. Thyroxin, which is important in brain development, estrogens and androgen, which are important in reproduction are also growth hormones with reference to human life. Estrogens released by girls’ ovaries and androgen released from the testes of the males contribute human reproduction. The physical growth of human beings however, cannot be viewed as similar to human beings that live in worldwide. Ethnic variations, hereditary and environmental factors affect physical growth of living beings (Santrock, 2001). Brain development should be understood in two levels: the microscopic level of individual brain cells and the larger level of the cerebral cortex. As the brain consists of hundred to two hundred billion neurons, the basic story of brain growth concerns how neurons develop and form their communication system. The neurotransmitters and synapses are very important physical constructions that support this system of communication. The rate of formation and performances of the synapses vary according to age. The rapid growth of synapses during the first two years of human life is a fine example of the combined efforts of various organs that facilitate this wonderful growth process. The cerebral cortex is the last brain structure to stop growing. Its ability to be sensitive to environmental influences for far longer than any other part of the brain suggests the massive duty performed by cerebral cortex in terms of growth and maturity. The cortical regions such as the frontal lobe that associate with the responsibility for thought function more effectively from age two months on. The connection of the frontal lobes and other brain areas bring rapid developments in communication during the teenage. Physical Development during Prenatal Stage and Infancy It is quite essential the functioning and proper physical formation of the brain. Different components of the brain are allocated for different motor skills, such as walking, talking etc. Infants begin life with a single cell and with the prenatal development of about nine months they are born to this world with approximately 100 billion neurons, having a brain and a nervous system (Berke, ) As the human embryo develops, during prenatal stage, the central nervous system is formulated as a long hollow tube on the embryo’s back. About three weeks later, human brain begins to develop, at its initial stage of development, as a large mass of neurons, being out of its tubular appearance. In the process of the development of the brain, along with the nervous system, there are three major stages; Cell production, Cell migration and Cell elaboration Cell production: - Most neurons are produced between 10 and 26 weeks after conception. Cell migration: - Moving of cells from the centre of the brain, where the neurons are produced, to their appropriate locations. Migration of cells is completed around seven months after conception. Growth of axons and dendrites of a cell and forming connections with other cells. Cell elaboration :- Begins immediately after cell migration, and starting from one’s birth remains continuing until old age. At birth, the new-borns’ brain is about 25% of its adult weight. After two years of rapid development, the infant’s brain becomes 75% of its adult weight. However, it is quite significant that the different areas of brain do not mature uniformly. Primary motor areas develop earlier than other primary sensory areas. As Santrock describes (2001) one researcher who is making strides in finding out more about the brain’s development in infancy is Charles Nelson. Charles Nelson attaches up to 128 electrodes to babies’ scalps and has found that even new-borns produce distinctive brain waves that reveal they are asleep. Other research conducted by Nelson has found that by 8 months of age babies can distinguish the picture of a wooden toy they were allowed to feel, but not see, from pictures of other toys. This achievement coincides with the development of neurons in the brain’s hippocampus (an important structure in memory), allowing the infant to remember specific items and events (p. 131). Stages of Prenatal Development Prenatal development takes place in three stages: germinal, embryonic, and fatal. During these three stages of gestation, the original single-celled zygote grows into an embryo and then a foetus. Development proceeds according to two fundamental principles both before and after birth. Growth and motor development occur from top to bottom and from the centre of the body outward. According to Papaila, Olds and Feldman also (2004) the cephalocaudal principal (from Latin, meaning “head to tail”) dictates that development proceeds from the head to the lower part of the trunk. An embryo’s head, brain, and eyes develop earliest and are disproportionately large until the other parts catch up. At 2 months of gestation, the embryo’s head is half the length of the body. By the time of birth, the head is only one-fourth the length of the body but is still disproportionately large. According to the proximodistal principle (from Latin, “near to far”) development proceeds from parts near the centre of the body to outer once. The embryo’s head and trunk develop before the limbs, and the arms and legs before the fingers and toes (p. 87). Brain Plasticity in Infancy and Early Childhood The brain is significantly plastic during the first few years of life. It can identify areas allocated to specific functions in which the mature brain cannot. However, the young brain is not exclusively plastic. When the brain is injured, its function is compromised. The plasticity of the brain is depended on factors including age, time of injury, site of injury and skill area. A large study of children with injuries to cerebral cortex, that occurred prior to birth or during the first six months, language and spatial skills were assessed repeatedly into adolescence. All the children experienced early brain seizures or haemorrhage. The brain imaging techniques MRI and PET revealed the precise site of damage. The language function is broadly distributed in the brain, thus, the damage to either hemisphere affected early language competence. The undamaged areas in either the left or the right hemispheres take over the language functions, at the age of children 5 catch up vocabulary and grammatical skills. Spatial skills were more impaired than the language after early brain injury. Children with early right hemispheric damage had problems with holistic processing. The left hemispheric damage capture the basic shape without fine-grained detail. The children with age show improvement in drawings but that do not occur in adults. Researchers speculated that the recovery after early brain injury is greater for language than spatial skills. Early brain injury has far less impact than the later injury on both language and spatial skills. Thus, the young brain is remarkably plastic. Children with early brain injury show deficits in a wide range of complex mental abilities during the school years. Their progress in math and reading is slow and produce simple narratives than peers without early brain damage. The correlation between the child’s score on intelligence tests with the amount of brain tissue damage is shown in infancy or early childhood. When healthy brain areas take over the function of damage areas, a crowding effect occurs. Multiple functions have to be performed by a smaller than usual volume of the brain tissue. The brain functions become slow and inaccurate. Complex mental abilities suffer into middle childhood and even persist longer. Brain plasticity is not restricted to early childhood. Reorganization of the brain can even occur in adulthood. Adult stroke victims display considerable recovery in response to stimulation of language and motor skills. Other Physical Advances in Brain development Apart from the cerebral cortex, numerous other brain areas make advances during childhood and adolescence. The cerebellum, supports in balance and control of body movement. Connection between the cerebellum and the cerebellum cortex supports thinking. It seems that children with damage to the cerebellum usually display both motor and cognitive deficits, including the problems with memory, planning, and language. The reticular formation maintains alertness and consciousness, generates synapses and myelinates from early childhood into adolescence. Many neurones in the reticular formation send out fibres to the frontal lobe of the cerebral cortex, contributing to improvements in continuous, controlled attention. The hippocampus plays a vital role in memory and in images of space that help us to find our way. During the preschool and school years, the hippocampus and surrounding areas of the cerebral cortex continue to develop swiftly, establishing connection with one another with the frontal lobes. The corpus callosum connects the two cerebral hemispheres. It supports smooth coordination of movements of both sides of the body, perception, attention, memory, language, problem solving and other aspects of thinking. Sensitive periods in Brain Development The brain is particularly sponge-like during the first few years, allowing children to acquire require skills easily and rapidly. The two types of brain development namely experience –expectant brain growth and experience- dependent brain growth characterize the appropriate stimulation during this time. The experience-expectant brain growth refers to the young brains rapidly developing organization, which depends on ordinary experiences, opportunities to see and touch objects to hear language and other sounds. If all infants, toddlers, and young children expect to encounter these experiences, they will grow normal. The experience dependent brain growth consists of additional growth and refinement of established brain structures because of specific learning experiences that occur throughout our lives, varying widely across individuals and cultures. Factors Affecting Physical Growth Physical growth is the result of the complex interplay between genetic and environmental factors. Environmental factors continue to affect genetic expression. Here, heredity is an important contributor to physical growth. Heredity determines the height and rate of physical growth based on adequate diet and health. As long as the environment is positive, the children and adolescent, show catch-up growth. Genes influence growth by controlling the body’s production of sensitivity and hormones. Mutation leads to deviation in physical size. Genetic also makeup affects body weight. Nutrition in Infancy Nutrition plays a vital role especially during the first two years because the baby’s body and brain are growing so rapidly. Twenty five per cent of babies’ total caloric intake is devoted to growth, and infants need extra calories to develop their rapid organic functions. Breast-feeding and bottle-feeding babies should be given the right kind of food. Breast milk ensures nutritional completeness. The World Health Organization recommends breast-feeding until age two years with solid food added at six month. Even it provides protection against respiratory and intestinal infections. Most mothers replace breast milk with commercial formula, or low-grade nutrition and cow or goat milk. The united nation has encouraged al maternal units and hospitals in developing countries to promote breast-feeding. Nutrition in Childhood and Adolescence All the basic food groups should include around 1 year. When the children approach 2 years their appetite become unpredictable. Parents need not worry about variation in amount eaten from meal to meal. This decline of appetite is the result of the slow growth rate. Children like to imitate their peers and adults food choices and eating practices. Parental control over eating limits children’s opportunities to develop self-control. Children’s healthy eating depends on a wholesome food environment. During puberty, rapid body growth leads to a dramatic rise in food intake. All age children adolescents are the most likely to skip breakfast, omit nutritional vegetables and fruit from their diet, consume lot of calories and eat. Fast food restaurants have begun to offer some unhealthy menu options but they need guidance in choosing the alternatives. The most common nutritional problem among adolescent is iron deficiency. Iron requirement increases to maximum during the growth spurt and remain high among girls because of iron loss during menstruation. Most adolescents do not get enough calcium and are deficient in riboflavin and magnesium. Malnutrition is widespread mostly in developing countries and war-torn areas, where food resources are limited. Recent evidence indicates that one third of the world children suffer from malnutrition before age five. Marasmus, Kwashiorkor is diseases caused by malnutrition that can impair body growth and cause damage to important organs (Berk, 2000). Malnutrition interacts with infectious diseases to weaken physical growth. Obesity is a rapidly rising problem in developing countries as urbanization shifts the population towards sedentary lifestyles and diets high in meat and refined foods. Obese children are often socially, emotionally isolated ones. In the same way, psychosocial dwarfism and non-organic failure to thrive are growth resulting from lack of parental affection and stimulation. Prolonged emotional deficiency can lead to permanent cognitive, emotional, and physical difficulties. Functions of Newborn Reflexes Though in the past it was considered that newborn or neonates are passive and helpless, careful observations of infant’s behaviour have proved that infants display many complex physical abilities (Berk, 2000). In relating to their physical world, infants are active from the birth. One main such physical development of infant’s is displaying a reflex that is considered as an automatic response to a particular form of stimulation. According to developmental psychologists, reflexes are the infant’s most obvious organized patterns of behaviour (Berk, 2000). Eye blink, rooting sucking swimming, moro, palmar grasp, tonic neck, stepping, babinski are the most common reflexes that infants display. According to researchers, the reflexes that have a survival value as rooting reflex helps to find the nipple of mother are called adaptive value of reflexes (Rochat & Hespos, 1997). In the same way, research studies prove that from the birth, babies are able to adjust the sucking pressure to how easily milk flows from the nipple (Craig & lee, 1999). In the same way, the moro - reflex helps babies to cling to their mothers when they were carried about all day. Some reflexes like tonic neck form the basis for complex motor skills that will deep later. It has proved that this tonic reflex encourages the baby to combine vision with arm movements and eventually real for to reach for objects (Knoblock & Pasamanick, 1974). Though some reflexes as palmar grasp, swimming and stepping drop out of the infant’s behavioural repertoire early, motor functions involved are renewed later with the gradual increase of involuntary control over behaviour as the central cortex delivery, reflexes disappear during first six months. In the same a way, research studies certify that infant sleep and cry also help the physical development. Throughout the day of night, babies move in and out of five states of arousal or degrees of sleep and fearfulness. The states regular or NREM, sleep, irregular or REM sleep, drowsiness, quiet alertness, waking activity and crying to alternate frequently. Researchers have found that newborns spend greater amount of five asleep - about 16 -18 hours a day (Davis, Paker & Montgomay, 2004). However, arousal steps become more organized with the age. Researchers have found that arousal patterns also have implications for early cognitive progress as learning as memory development (Gesrter, et al. 2002, Gouez, Bootzin & Nadel, 2006). In the same way, they have found that stimulation of REM sleep helps for the growth of the central nervous system. Physical Development and Neonatal Behavioural Assessment scale (NBAS) One of most important physical assessing instruments of new-born babies is neonatal behavioural assessment scale (NBAS), and this evaluates the babies’ reflexes, muscle tone, state changes responsiveness of physical and social stimuli and other reasons (Braxelron & Nugent, 1995). Recently developed neonatal Intensive care Unit Network Neurobehavioral scale (NNNs) is designed for use with new-borns at risk for developmental problems because of low birth weight, pattern delivery, prenatal substance exposure or other conditions (Lester & Tronick, 2004). Lester and Tronick, (2004) also have found that details about individuals and cultural differences in newborn behaviours and how child rearing practice can maintain or charge a body’s reactions. Combination between Physical Development and Learning Capabilities of Infants Simply, learning means the changes in behaviour as the result of experience. Researches prove that babies have two learning capabilities - Classical Conditioning and Operant conditioning. In classical conditioning, a neutral stimulus is paired with a stimulus that reads to a reflexive response. Once the baby’s nervous system makes the connection between the two stimuli, the new stimuli is will produce the behaviour itself. As research studies certify when the association between two stimuli has a survival vale, infants can be classically conditioned. In operant conditioning, babies act or operate on the environment are stimuli that follow their behaviour change the probability. For an instance, sweet liquid reinforces the sucking response of newborn. Removing a desirable stimulus is called a punishment. A sour tasting fluid punishes the baby from sucking. Researchers have found that sucking of nipple produces a variety of interesting sights and sounds. They suck farther to see visual designs or to hear music and human voices. (Floccia, Chrisstophe & Bertoncini, 1997). Motor Development in Infancy Virtually all parents eagerly await mastery of new motor skills, recording with pride when their infant first hold up their heads, reach for objects, sit by themselves, and walk along. Parents’ enthusiasm for these achievements makes perfect sense. Babies’ motor achievements have a powerful impact on their social relationships. Parents increase their expressions of affection and playful activities as their independently moving baby seeks them out for greetings, hugs, and a gleeful game of hide and seek. Certain motor skills, such as reaching and pointing, permit infants to communicate more effectively. Motor skills, emotional and social competencies, cognition and language develop together and support one another. The Sequence of Motor Development Gross motor development refers to control over actions that helps infants get around in the environment, such as crawling, standing and walking. Fine motor development has to do with smaller movements, such as reaching and grasping. Each skill is a product of earlier motor attainments and a contributor to new ones. Children acquire motor skills in highly individual ways. Many factors, both internal and external to the child, influence waste transformations in motor competencies of the first two years. Motor skills as dynamic systems According to dynamic system theory of motor development, mastery of motor skills involves acquiring increasingly complex systems of actions (Berk, 2000). When motor skills work as a system, separate abilities blend, each cooperating with others to produce effective ways of exploring and controlling the environment. Each new skill is a join product of central nervous system development, the body’s moment capacities, the goals the child has in mind, and environmental supports for the skills. The factors that induce change vary with age. In the early weeks of life, brain and body growth are especially important as infants achieve control over the head, shoulders, and upper torso. Late the baby’s goals and environmental supports play a greater role. Characteristics of the broader physical world also profoundly influence motor skills. When a skill is first acquired, infants must refine it. As moments are repeated thousands of times, they promote new connections in the brain that govern motor pattern. Fine Motor Development: Reaching and Grasping Of all motor skill, reaching may play the great role in infant cognitive development. By grasping things, turning them over, and seeing what happens when they are released, infant learn a great deal about the sights, sounds, and feel of objects. Reaching and grasping, like many other motor skills, start out as gross, diffuse activities and move toward mastery of fine moments. New-borns also make poorly coordinated swipes, called pre-reaching, toward an object in front of them, but because of poor arm and hand control, they rarely contact the object. Development of reaching and grasping at about three to four months, as infant develop the necessary eye, head and shoulder control reaching objects as purposeful, forward arm moment in the presence of a nearby toy and gradually improves in accuracy. By four months, infant reach for a glowing object in the dark. At five to six months, they reach for an object in a room that has been darkened during the reach by switching off the lights, a skill that improves over the next few months. When vision is freed from the basic act of reaching, it can focus on more complex adjustments, such as fine turning actions to fit the distance and shape of objects. Reaching improves as depth perception advances and as infants gain greater control of body posture and arm and hand movements. After seven months, infants become better at reaching for moving objects, ones that spin, change direction, or move closer or farther away. Once infants can reach, they modify their grasp. The new-borns grasp reflex is replaced by the lunar grasp, a clumsy motion in which the baby’s fingers close against the palm. Still, even three months olds adjust their grasp to the size. Around four to five months, when infants begin to sit up, they no longer need their arms to maintain body balance. They frequently transfer objects from hand to hand. By the end of the first year, infants use the thumb and index finger opposably in a well-practiced, freeing attention from the motor skill to events that occur before and after obtaining the object. Around this time, too, infants begin to solve simple problems that involve reaching, such as searching for and finding a hidden toy. Finally, the capacity to reach for and manipulate an object increases infants’ attention to the way an adult reaches for and plays with that particular object. Perhaps with the aid of mirror neurons, babies match their own active experience of reaching to their perception of others’ behaviours and as they watch what others do, of the range of actions that can be performed on various objects. Trying to push infants beyond their current readiness to handle stimulation can undermine the development of important motor skills. Impact of Physical Development on Perception Humans depend on vision more than any other sense. At birth visual components of the brain and the eye are not completely formed. For instance, muscles in the lens, cells in the retina, the optic nerve etc. is not functioning properly, at the initial stage of one’s life. The visual system develops rapidly over the first few months. Although the infants cannot see properly, they actively explore their environment. Their eye-movements are also comparatively slow. First, they capture fuzzy images of objects that are around him, and then (he/she) they figure out the characteristics of objects and how they are arranged in space. Gradually, they become capable of identifying that the objects so far perceived, are not flat but three dimensional, with the ability of depth perception. Researchers have found the utmost importance of motor skills in perceptual development as well. For instance, control of the head during the early weeks of life may help babies notice motion and binocular cues. Simultaneously, the ability to turn, poke and feel the surface of objects may promote sensitivity to pictorial cues. Moreover, it we examine an infant’s crawling experience, it promotes a new level of brain organization. Perhaps, crawling strengthens certain neural connections. Infants who see poorly, have great difficulty in maintaining the healthy, relationship with the care-giver. They cannot make eye contact, imitate or pick-up non-verbal social cues. They are greatly delayed in establishing a shared focus of attention on objects. Moreover, to reach for and manipulate objects maintain balance or move across various surfaces infants must continually coordinate their motor behaviour with perceptual information. Instead, motor activity is a vital means for exploring and learning about the world and improved perception brings about more effective motor activity. Young infants perceive their senses. Baby’s sensitivity to touch, taste, and smell, sound and visual stimulation have a close relationship with physical development. Touch helps stimulate early physical growth, and it is vital for emotional development. The newborn baby responds to touch, especially around the mouth on the palms and on the soles of the feat. Newborns use touch to investigate their world. When considering taste, infants relax their facial muscles in response to sweetness, purse their lips when the taste is sour, and show a distinct arch like mouth opening when it is bitter. It’s help for survival. New-borns’ dual attraction to the odour of their mother and to that of breast milk helps them locate and appropriate food source and, in the process, begin to distinguish their caregiver from other people. Although conduction of sound through structures of the ear and transmission of auditory information to the brain are inefficient at birth, research studies certify that new-born infants can hear a wide variety of sounds and this sensitivity improves greatly over the first few months. Young infants listen longer to human speech than structurally similar non-speech sounds. In addition, they can detect the sound of any human language. So above facts clearly prove that perception also have close connection with physical development. The theories like psychodynamic, system, ethology and life span etc. talk about human development relative to physical development. For an instance, Freud’s psychodynamic theory of psychosexual development has a close connection with physical development. The stages; oral, anal, phallic, latency and genital have physiological background. So we can see that how important physical development is for other development areas of human being. When considering above facts, it is clear that physical and motor development of humans hold a very important palace in the life of human beings. Infants’ physical and motor development lay the foundation to build a healthy human being. Therefore, each and every physical and motor action of an infant has a great value. Conclusion Physical and motor developments of infants hold a very important place in developmental psychology. Infants display various physical and motor skills when they grow and they are physically and mentally active agents of learning and they are not helpless. From the conception, infants physically develop and after birth, they show a gradual physical and motor development. Infants’ physical and motor development occurs both inside and outside. Brain, nervous system, hormone system, and muscles etc. of infants have close relationship with physical development and as a whole, all the physical entities with the mentality contribute for the physical and motor development of infants. References Berk. L., (2009).Child Development, (8th ed.) New Delhi : PHI Learning Pvt. Ltd. Parke, R. D., & Locke, V.O., (1999). Child Development. (5th ed.). McGraw Hill: New York. Santrock, J. W., (2010). Child Development. (9th ed.) New York: McGraw Hill Companies.