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Chapter 7

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PSYC 2450
Anneke Olthof

Chapter 7 o Sensation: process by which sensory receptor neurons detect information and transmit it to the brain o Perception: interpretation of sensory input: recognizing what you see, understanding what is said to you, or knowing that the odor you’ve detected is fresh-baked bread o Learning is the process by which our behaviors change as a result of experience  Early controversies about sensory and perceptual development  Nature versus nurture o Empiricist philosophers believed that an infant had tabula rasa and must learn to interpret sensations o Navist philosopher (Rene Descartes and Immanuel Kant) took the nature side of nature/nurture issue arguing that many basic perceptual abilities are innate o Today’s developmentalists take less extreme stand on this nature/nurture issue. They recognize that the perceptual world of a human neonate is limited and both maturational processes and experience contribute to growth of perceptual awareness  Enrichment versus differentiation o Objective reality to which we respond o Enrichment theory: specifies that we must add to sensory stimulation by drawing on stored knowledge in order to perceive a meaning world o Differentiation theory: theory specifies that perception involves detecting distinctive features or cues that are contained in the sensory stimulation we receive o Distinctive features: characteristic of a stimulus that remain contains; dimensions on which 2 or + objects differ and can be discriminated (also called invariances or invariant features)  Research methods used to study the infants sensory and perceptual experiences  The preference method o This method is a simple procedure in which at least two stimuli are presented simultaneously to see whether infants will attend more to one od them that the others  Determine if young infants could discriminated visual patterns  Ability to detect and discriminate patterns is innate  Short coming: if infant shows no preference to stimulus; not clear of she or he failed to discriminate them or found them equally interesting  The habituation method o Process in which a repeated stimulus becomes so familiar that responses initially associated with no longer occur  Simple form of learning also known as familiarization novelty procedure  Dishabituation: showing a change in respiration or heart rate when presented a another stimulus  To categorize infant looking behaviors, researchers must pay carful attention to the familiarization time line of each infant being tested 1  The evoked potentials method o Evoked potential: a change in patterning of the brain waves that indicated that an individual detects (senses) a stimulus  The high-amplitude sucking method o Method of assessing infants perceptual capabilities that capitalizes on the ability of infants to make interesting events last by varying the rate at which they suck on a special pacifier  Infants can exert enough control over their sucking behavior to use it to show us what they can sense and to give us some idea of their likes and dislikes  Can be modified to let the infant tell us which of two stimuli is preferred  Infant sensory capabilities  Hearing o Using evoked potentials method researches have found that soft sounds that adult hear must be made noticeably louder before a neonate can detect them o Habituation studies indicate that neonates are capable of discriminating sounds that differ in loudness, duration, direction and frequency  Reaction to voices - Young infant are particularly attentive to high pitch feminine voices and they can recognize their mother voice - Research by Anthony DeCasper reveals that newborns suck faster on a nipple to hear a recording of their mother’s voice than a recording of another woman  Reaction to language - Phonemes: able to discriminate basic speech sounds early in life  Can recognize phonemes from other languages and can recognize words that they hear often at about 1 year, infants turn in response to their own names when the names are only 5 decibels louder than background voices - Hearing in highly developed at birth, but infants in their first six months of life are not always consistent in responding to noises when noises are presented to them (U-shaped curve; see box 7.2) - Otitis media: common bacterial infection of the middle ear that produces mild to moderate hearing loss  Taste and smell o Infant suck faster and longer for sweet liquids than for bitter, sour, salty or neutral (water) solutions and different tastes elicit different facial expression from newborns  Sweet reduce crying and produce smiles and smacking of lips, whereas sour substance cause infants to wrinkle their noses and purse their lip, bitter solutions elicit expressions of disgust o Newborn are capable of detecting a variety of odors and they react vigorously by turning away and displaying expressions of disgust in response to unpleasant smells like vinegar, ammonia or rotten eggs  A 1 to 2 week-old breastfed infant can already recognize her or his mother by the smell of her breast and underarms 2  Touch, temperature and pain o Sensitivity to touch enhances infants responsiveness to their environments and newborns are sensitive to warmth, cold and changes in temperature o 1-day-old infants cry loudly when pricked by a needle for a blood test. Young infants show greater distress upon receiving an inoculation than 5- to 11-months old o Male babies are highly stressed by circumcision  Babies treated with a mild topical anesthetic and given a sugary solution to suck are less stressed by this operation  Vision o Least mature of a newborns sensory capabilities changes in brightness will elicit a subcortical papillary reflex, which indicates that the neonate is sensitive to light, they can detect and track movement as long as it is moving slowly and they are more likely to track faces than other patterns, although this preference for faces disappears within 1 or 2 months o By 2 or 3 months of age, babies can discriminate all the basic colors and by 4 months they are grouping colors of slightly different shags into the same basic categories o Very young infants do not resolve fine detail very well  Visual acuity: suggest that a neonate’s distance vision is about 20/600, which means that she sees at 6 m what an adult with excellent vision sees at 183 m  Visual contrast: amount of light/dark transition in a visual stimulus. Require sharper vision than adults do, but by 6 months, babies visual acuity is about 20/100 and by age 12 moths the see about as well as adults do (See table 7.1 for a summary)  Visual perception in infancy  Perception of patterns  Early pattern perception (0-2 months) - Fantz’s test with the normal, scrambled face; infants interesting in both - Very young infants prefer to look at high contrast patterns with many sharp boundaries between light and dark areas, and at moderately complex patterns that have curvilinear features - Prefer to look at moderately complex checkerboard over highly complex and those that capture their attention by moving  Later form perception (2 months to 1 year) - Between 2 and 12 months of age, the infants visual system is rapidly maturing - Ability to use object movement to perceive form is apparently not present at birth but has developed at 2 months  Explaining form perception - Newborns are biologically prepared to seek visual stimulation and make visual discriminations (keeps the visual neurons firing and contribute to the maturation of the visual centres of the brain) 3 - By about 2 to 3 months of age, maturation has progressed to the point of allowing an infant to see more detail, scan more systematically and begin to construct visual forms, including ones for faces and more specific configurations that represent the faces of familiar people - Infant’s visual acuity limits input to large objects with high contrast in infancy appear to reserve the neural tissue for later refinement - The growth of form perception results from a continuous interplay or interaction among the baby’s inborn equipment  Perception of three-dimensional space o Infants younger than 2-3 months of age do not exhibit any stereopsis: convergence of the visual images of the two eyes to produce a singular, non-overlapping image that has depth o Nativists argue that several cues to depth and distance are monocular (detectable with only one eye) o Artists make good use of other pictorial or perspective cues to create the illusion of 3- dimension on a 2-dimension surface (e.g. linear perspective, texture gradients, sizing cues, interposition and shading)  If neonates can detect these monocular depth cues, then their world may be 3- dimensional from beginning  Size constancy - Visual looming: expansion of the image of an object to take up the entire visual field as it draws very close to the face - Size constancy: tendency to perceive an object as the same size from different distances despite changes in the size of its retinal image  Doesn’t emerge until 3 to 5 months of age; after infants had developed good binocular vision (stereopsis) that would help them make accurate inferences  Size constancy steadily improves throughout the first year, however this ability is not fully mature until 10-11 years  Use of pictorial cues - Infants become more sensitive to different spatial cues at different ages  From a limited capacity for size constancy at birth, babies extract spatial information from kinetic cues: cues created by movements of objects or movements f the body; provide important for the perception of forms and spatial (between 1 and 3 months and binocular cues at 3-5 months and monocular cues by age 6-7 months)  Development of depth perception - The visual cliff consist of an elevated glass platform divided into two sections by a centre board  On the shallow side, a checkerboard pattern is placed directly under the glass and on the deep side the pattern is several feet below the glass, creating the illusion of a sharp drop off  90 % cross the shallow side but 10% would cross the deep side  6 months old fear of drop off but 2 months old have not learned to fear drop-offs (Most of crawling age perceive depth and are afraid of drop-offs) 4  Motor development and depth perception o Many 6-7 months old come to fear drop-offs because they are more sensitive to kinetic, binocular and monocular cues that younger infants are  Motor development provides experiences that change infants interpretation of the meaning of depth o Self produced movement makes an infant more sensitive to optical flow  Sensation that other objects more when he or she does. Which promotes the development of new neural pathways in the sensory and motor areas of the brain that underlie improvements in both motor skill and spatial perception o Interactive model: best explains the growth of form perception applies equally well to the development of spatial abilities  Maturation of the visual sense enables infants to see better and detect a greater variety of depth cues, while also contributing to the growth of motor skills See table 7.2 for a summary of the changes in visual perception that occur during the first year of life)  Intermodal perception o This is the ability to use one sensory modality to identify a stimulus or
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