Chapter 5: Perceptual and Physical Development in infancyPhysical Growth in the first two years• The average newborn weighs 7 ½ lbs. and measures about 20 in. • Birth weight typically doubles by 5 months (to 15 lbs.) and triples by first birthday (22 lbs.)• Breastfeeding and formula are both nutritionally acceptable, breastfeeding offers several important health advantages such as:- Changes as your baby grows- Easier to digest- Fights disease The Development of the Brain• Central nervous system: includes the brain, most complicated physical structure in the body• Nerve cell production stops just before birth, but structure of brain continues to evolve through first ten years of life• Synapse: structured to allow impulses to be conducted from cell to cell by chemicals known as neurotransmitters. • Plasticity of the brain: the ability for other parts of the brain to take over and function.I.e. hemispherectomy: removal of half a child’s brain • By second year synapses begin to disappear; pathways hat get used repeatedly survive, those they get unused disappear- “Use it or loose it”• Pruning: process of the nervous system eliminating senates and cells that have no function or purpose. - Occurs mostly during adolescence • Until further research it is recommended to parents and practitioners for “early brain stimulation” to remain speculative. Sensory and Perceptual development in infancyHow infant perception is studied:• Sensation: refers to the ability to register information concerning internal and external events, and to transmit that information to the central nervous system. • Perception: refers to the processing of sensory information by the brain. • Visual preference method: researchers present pairs of stimuli to baby, then observes the infant from hidden vantage point between two stimuli, then detects which stimulus baby is looking at. • Method of event-related potentials: electrodes attached to infants scalp to measure changes in electrical activity in the brain in response to changing stimuli presented to the infant.• Habituation-Dishabituation procedure- Habituation: intensity of responses steadily decrease; become less interested- Dishabituation: Infants changes response and notices the change in stimulus• High-amplitude sucking technique: internal sensing device that indicates when infants rate or intensity of sucking increases. (visual or auditory stimulus)The development of visual perception • Retina: a complex layered tissue on the back surface of the eye made up of light-sensitive cells and nerve cells. • Fovea: a densely packed set of highly sensitive cells at the center of the retina (detail)• Visual acuity: sharpness of vision - Newborn vary 20/500 • Ciliary muscles: bend (or focus) light waves reflected off objects at varying distances toward the fovea. Tracking moving objects in space• Smooth pursuit movements enable infants to track movement of objects in space• By the fourth month infants’ visual acuity can discriminate considerable detailSeparating figure from ground• Differentiating objects as separate entities • Infants are best able to make out objects they see frequently and that move in relation to other objects and backgrounds Depth perception: Objects in 3- dimensional space• Infants learn to process three types of visual information:1. Binocular information: the different locations of the two eyes in the heado Reasonably developed by about 4 months2. Kinetic information: when infants head moves side to side, the image of near objects moves more rapidly across retinal surface than image of more distant object• Visual cliff: measure depth perception; crawling infants placed on sheet of plate glass that creates illusion of a drop-off as infant crawls across it. 3. Pictorial information: perspective (objects of equal size are judged closer or farther away by their relative size in picture) and superimposition (objects that block out the view of other object are judged to be closer.)o Develops between 5 and 7 monthsAuditory Perception• The ear is developed several weeks before birth• By 6 months, the auditory system’s ability to detect different intensities of sound and variations in pitch is highly mature• Newborns can locate sounds to the left or right of the head, but that ability declines over next two months about comes back around 4 monthsPerception of speech sounds• High amplitude sucking technique demonstrates neonates notices difference between sounds.• Scientists now believe that newborns possess innate perceptual mechanisms that facilitate the development of language • Websource:- Babies start to develop language at birth- Hearing loss can be found early• You can promote your baby’s ability to localize sound by providing an environment that is rich in sounds that come from easily identifiable sourcesOther Sensory DevelopmentsTaste and Smell• Sensitivity to taste is present soon after birth • Display slight smile when sucking movements to sweet substances; purse the lips and wrinkly the nose and blink to sour substances; spit up and choke on bitter substances. • Newborns sense of smell develops rapidly during the neonatal period• Sense of smell may play important role in bonding breastfeeding mothers to infants• Study showed that mothers recognized the smell of their 1-2 day old babies. • Websource: Experiments were done to prove that babies do in fact feel pain; it is not just a reflexDeveloping Motor ControlReflex Behaviors• Reflexes: involuntary stimulus-response patters • Innate reflexes in human infants:- Rooting: turns hear, opens mouth and suck when check is stroked- Stepping: steps when feet contact surface- Moro: sudden arching of the back and grasping motions of arms to loud noise of loss of support- Babinski: toes fan out and foot curls when sole of foot is stroked- Grasping: grasp in response to pressure in plam- Tonic neck: head to one side and body in fencer position- Sucking: sucking to oral stimulation- Eye blink: rapid closing of eye to sudden light or air puff• Cerebral cortex has very little effect on behavior of newborn• Reflexes are controlled by clusters of cells within the brainstem• Brain stem is most highly developed component of central nervous system at birth; purpose is to receive impulses from sensory receptors and transmit second input to musculature for specific motor response•
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