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Chapter 7

Chapter 7 textbook notes 4th ed

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PSYC 2110
Raluca Barac

Chapter 7: Early Cognitive Foundations: Sensation, perception, and Learning Sensation: our senses detect stimuli from the environment and encode the information as neural signals. • Process by which sensory receptor neurons detect information and transmit it to the brain. • React to sounds, tastes, odour and are likely to cry up a storm when poked by a needle. • Energy from the environment is detected and transformed into neural signals. Perception: categorization and interpretation of sensory stimulation based on experience • Is the interpretation of sensory input: recognizing what you see, understanding what is said to you, or knowing that’s the odour you’ve detected is fresh baked bread. • Energy from the environment is selected and interpreted by the brain. Research Methods Used to Study Infants’ Sensations and Perceptions The Preference Method • present babies with two stimuli simultaneously; measure the time babies spend looking at each (to see whether infants will attend more to one of them than the other(s). • They use their perceptual abilities • Newborns could easily discriminate (tell the difference between) visual forms, and they prefer to look at patterned stimuli (faces or concentric circles). • Ability to detect and discriminate patterns is innate • If an infant shows no preferences among the target stimuli, it is not clear whether they failed to discriminate them or simply found them equally interesting. The Habituation Method (most popular) • present babies with a repeated stimulus and, once infants show habituation, introduce a new stimulus; dishabituation • The process in which a repeated stimulus becomes so familiar that responses initially associated with it (head/eye movements) no longer occur • It is a form of learning. Can be called “familiarization- novelty” • To test infants ability to discriminate 2 stimuli that differ in some way you must: 1) present one of the stimuli until the infant stops attending/responding (habituates). Then the 2nd stimulus is presented. If the infant discriminates this 2nd stimulus from the 1st he/she will dishabituate- that is attend closely to it while showing an change in respiratory/ heart rate. • Infants display preference when they are familiar with- but not too familiar with a stimulus. When presented with 2 stimuli infants initially show no preference- don’t look at one thing more than the other • When one stimulus does capture their attention, they begin to look at it more often and for a short time, when presented with this partially familiar stimulus and a unfamiliar stimulus they spend more time looking at the partially familiar stimulus. • When they become familiar with the original stimulus, they become ready to move on and will spend less times looking at the familiar stimulus than its unfamiliar partner. The Evoked Potentials Method • examines brain-wave patterns as infants process information • Electrodes are placed on the infants scalp above those brain centres that process the kind of sensory information (EEG cap used) • Responses to visual stimuli are recorded from the back of the head (occipital lobe), and sounds are recorded from the side of the head, above the temporal lobe. • If the infant senses the particular stimulus present, she will show a change in the patterning of her brain waves or evoked potential • This evoked potentials can tell whether infants can discriminate various sights, sounds because 2 stimuli that are sensed as “different” produce different patterns of electrical activity. The High-Amplitude Sucking Method • conclusions about infants’ discrimination abilities are made based on infants’ sucking behaviour • Provides infants with special pacifier containing electrical circuitry that enables them to exert some control over the sensory environment. • Whenever the infant sucks faster or harder than before (high-amplitude sucking) the infant trips the electrical circuit in the pacifier, thereby activating a slide projector/ tape recorder that introduces some kind of sensory stimulation. Once the infants interest wanes and her sucking returns to normal, the stimulation stops • If the investigator then introduces a 2 ndstimulus that elicits an increase in high-amplitude nd susting he/she can conclude that the infant has discriminated the 2 stimulus from the 1 . • This procedure can be modified to let the infant tell us which to the two stimuli is preferred. Sensations and Perceptions 1) Hearing • Using the evoked potentials method, researchers have found that soft sounds that adults can hear must be made noticeably louder before a neonate can detect them • First few hours of life, infants may hear about as well as an adult with a head cold. • Their insensitivity to softer sounds can be due to fluids that have seeped into the inner ear during the birth process • Neonates are capable of discriminating sounds that differ in loudness, duration, direction and frequency and do it easily • At 4-6 months infants react to a approaching auditory stimulus in the same way that they react to a approaching visual stimuli: they blink in anticipation of a collision • They are attentive to voices, especially high pitched feminine voices • Newborns suck faster on a nipple to hear recording of their mothers voice than a recording of another woman • Fetuses in their third trimester experience changes in their heart rate when responding to information provided by mothers. Indicating that fetuses were learning sound patterns before birth • Responsiveness to mother’s voice after birth may even be highly adaptive if it encourages a mother to talk to her infant and to provide the attention and affection that foster healthy social, emotional and intellectual development. • Learning the mother’s voice occurs under naturalistic conditions with no environmental manipulation necessary. • Infants may need to see facial expressions to help them distinguish adult emotional states • Babies not only attend closely to voices but also areable to discriminate basic speech sounds called phonemes- very early in life • Infants 2-3 months old could distinguish consonant sounds that are very similar (ba, pa). Infants less than 1 week old can tell the difference between the vowels a and I and even segment words into discrete syllables • Learning, phonemes and words is slightly delayed in babies from bilingual homes. They seem to divide speech sounds into categories corresponding to the basic sound units of language • 3-6 month old infants are actually better than adults are at perceiving certain phonemes (smallest meaningful sound units that make up a spoken language) that are not part of the language their companions speak • Babies soon learn to recognize words that they hear often. By 4 ½ months, they will turn their heads to hear their own name but not to hear other names • Babies this young probably do not know that the word for their name refers to them but they are able to recognize frequently heard words very early in life • At 5 months if the speaker is loud enough, infants are able to detect their own names against a background of babbling voices. The volume of the spoken name must be around 10 decibels higher than the background voices • At about 1 year infants turn in response to their own names when the names are only 5 decibels louder. • Hearing is highly developed at birth- but in the first 6 months they are not always consistent with responding to noises when noises are presented to them • Infants at first always turn to the side where a sound is presented, than they seem to stop responding and than at a later time start responding again • Although a baby’s hearing improves over the first 4-6 months, even newborns are well prepared for such achievements as 1) Using voices to indentify and discriminate their companions and 2) segmenting speech into smaller units- the building blocks of language. 2) Vision May be the least mature of the newborns sensory capabilities • Changes in brightness will elicit a subcortial papillary reflex, which indicates that the neonate is sensitive to light • Babies can detect movement in the visual field and are likely to track a visual stimulus with their eyes as long as the target moves slowly • New born infants are more likely to track faces than other patterns- although is preference for faces disappears within 1-2 months • Infants just minutes old could track a visual stimulus with their eyes and heads and that they showed a preference for the human face- maybe due to an adaptive remnant of our evolutionary history- a reflex controlled by subcortial areas of the brain, that serves to orient babies to their caregivers and promote social interactions • Neonates see the world in colour, but they have trouble discriminating blues, greens, and yellows from whites • By 2-3 months babies can discriminate all the basic colours and by 4 months they are grouping colours of slightly different shades into the same basic categories. • Studies of 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. • Objects at any distance look rather blurry to a very young infant who has trouble accommodating- that is changing the shape of the lens of the eye to bring visual stimuli into focus, simply needs sharper visual contrasts to “see” them than adults do. • By 6 months babies’ visual acuity is about 20/100 and by age 12 months they see about as well as adults do. • Newborns can sense movement, colours, changes in brightness and a variety of visual patterns-as long as these patterned stimuli are not too finely detailed and have a sufficient amount of light/dark contrast. • As infants explore the world with their eyes, experience-dependent mechanisms- such as synaptic reinforcement- begin to contribute to the development of visual acuity. • Both experience-independent and experience-dependent mechanism promote development of the infants visual system Visual perception in infancy • Babies only 2 days old could easily discriminate visual patterns (face most preferred) • 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 • Babies less than 2 months old see only a dark blob when looking at highly complex checkerboard • Babies prefer to look at whatever they see well and the things they see best are moderately complex, high contrast targets, particularly those that capture their attention by moving • Researchers believe that 1-2 month old infants detect few if any forms because they see so poorly and they scan visual stimuli in a very limited way. So unless the form is very small, they are unlikely to see it all • Between 2-12 months the infant’s visual system is rapidly maturing. They see better and is capable of making complex visual discriminations- being able to discriminate temporal movement sequencing • The infant is also organizing what he or she sees to perceive visual forms and sets of separate forms. • The most basic task in perceiving form is to discriminate that object from its surrounding context (that is, other objects and the general background) • Infants rely heavily on kinetic motion cues to indentify distinct forms • Ability to use object movement to perceive form is apparently not present at birth but has developed by 2 months of age • 3-4 month infants can perceive form in some stationary scenes that capture their attention- perceiving subjective contours such as a “square” (mentally) • At about 8 months infants no longer need kinetic cues to perceive a partially obscured rod as a whole • 12 month olds prefer to look at actual objects with different shapes- indicates that they have perceived the form traced earlier by the light and now find it less interesting than other forms. • Three important pieces of information that we have to be able to process are the shape, or contours, of the individuals head (jaw line), the shapes of individual features (mouth), and the spacing among the features (eyes). Explaining Form Perception • After birth the infants visual acuity limits input to large objects with high contrast • Newborns are biological prepared to seek visual stimulation and make visual discrimination- important because they keep the visual neurons firing and contribute to the maturation of the visual centres of the brain. • About 2-3 months maturation has progressed to the point of allowing an infant to see more detail, scan more and begin to construct visual forms, including one for faces and familiar companions • Children treated for cataracts developed normal skills in differentiating the shapes of faces and individual features, they showed deficits in their ability to discriminate among faces that differed in the spacing of features • The visual input from large objects with high contrasts in infancy appears to “reserve the neural tissue for later refinement” • Growth of form perception results from a continuous interplay or interaction among the baby’s inborn equipment, biological maturation and visual experiences Perception of three- dimensional space • Empiricists have argued that poor visual acuity and inability to bring objects into sharp focus (that is, to accommodate) prevent the neonate from making accurate spatial inferences • Infants younger than 2-3 months do not exhibit stereopsis- a convergence of the visual images of the two eyes to produce a singular, non-overlapping image that has depth perception. (fusion of two flat images to produce a single image that has depth) • Nativists argue that several cues to depth and distance are monocular- that is, detectable with only one eye. Movement of objects (such as th
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