PERCEPTUAL DEVELOPMENT CHAPTER 16

Transcription

1 PERCEPTUAL DEVELOPMENT CHAPTER 16 Overview f Questins What can newbrns perceive? When can an infant perceive clr? Can a newbrn recgnize his r her mther? INFANT BRAIN DEVELOPMENT At birth babies brain has almst all the neurns it will ever have, but Perceptual Develpment 1 Brain is f its adult weight at birth, and by 4 yrs. Brainstem and Midbrain are Pstnatal Grwth: METHODS OF STUDYING PERCEPTIONAL DEVELOPMENT Fr a lng time, thught perceptual abilities at birth & infancy were minimal: partly due t Hw can we pssibly knw what a baby sees, hears, smells, and perceives when she can't tell us abut it? Measures f Attentin: Preferential Lking Measures f attentin: state f alertness r arusal fcused n a specific aspect f envirnment. Preferential Lking 2 stimuli are presented t the infant and if she stares at ne lnger than the ther, the experimenter cncludes. Spntaneus Lking Preferences: Special phtgraphic techniques

2 Perceptual Develpment 2 Measures f Attentin: Physilgical Respnse Measures Orienting Respnse: behaviral and physilgical changes that ccur when a stimulus is first presented. Autnmic Nervus System respnse t stimulatin CNS respnse: Habituatin Dishabituatin Use f Learning Principles t Study Infant Perceptin Habituatin-Dishabituatin Paradigm The habituatin-dishabituatin sequence is used t explre whether infants can perceive differences between stimuli. Operant Cnditining Operant cnditining is a frm f learning in which a behavir is fllwed by a stimulus that changes the prbability that the behavir will ccur again. A reinfrcer is a stimulus that the ccurrence f a respnse. Operant cnditining allws researchers t determine what stimuli babies perceive and which nes they. Used a lt fr explring infant hearing: High amplitude sucking (Peter Eimas) INFANT VISION Visin is the f the newbrn baby s senses. Infants are and reasns fr this are 2 fld: Retinas: Newbrns dn t have enugh functining in their retinas, but the appears adult-like. Immaturity f Visual Crtex: dn t have enugh in visual crtex. Visin Develps rapidly: Infants begin t perceive patterns, bjects, and depth w/in the first. At ne mnth ld visual acuity is apprximately. Increases rapidly ver the first 6 mnths f life.

3 Preferential Lking & Visual Acuity Perceptual Develpment 3 Pairing stimuli with different frequency stripes t gray stimulus and bserve preferential lking. The clser tgether the stripes the mre difficult the discriminatin (greater VA) Visual Acuity Visual Evked Ptential (VEP): are placed n the back f the infant s head, ver the. The infant lks at a gray field which is briefly replaced by either a grating r a checkerbard pattern. If stripes r checks are detected the. If the pattern cannt be detected n VEP is generated. Cntrast Sensitivity Measured by determining the smallest difference between light and dark bars f a grating that can be detected. Spatial frequency - number f cycles f the grating per visual angle Cntrast sensitivity functin - plt f cntrast sensitivity versus spatial frequency Infant s ability t perceive cntrast is restricted t. At these lw frequencies the infant s cntrast sensitivity is by a factr f 20 t 100. Infants can see little r nthing abve, which is an adult s mst sensitive range. The visin f a is slightly wrse than : Infants see n fine details and can see nly relatively large bjects with high cntrast. Undevelped state f infant s fvea frces the infant t see primarily with

4 Object Recgnitin: Recgnizing Mm s Face A ld infant can recgnize his mther s face. Perceptual Develpment 4 Bushnell, Sai, & Mullin (1989) Using the preferential lking paradigm fund that infants spent f the time lking at mm vs. fr stranger. Waltn et al. (1992) fund that infants respnd mre t mm than stranger when videtape images are used. Hw d infants discriminate between mm and stranger? Pascalis et al (1995) fund that when mm wre a Perceiving Object Unity Kellman & Spelke (1983): Habituated 4 mnth lds t a rd mving back and frth behind a blck. They then presented either 2 separate rds r a single lnger rd. Dishabituatin Perceived the partial ccluded mving rd. Imprtance f Mvement: Perceptin f unity desn t ccur when infant is habituated t a rd and blck display. Slater et al (1990) repeated the Kellman & Spelke experiment n. Results: Newbrns lk lnger at the during dishabituatin. Rd behind the blck = Jhnsn et al. (2004) used the same technique as Kellman and Spelke and als recrded eye mvements 3-mnth-ld perceivers fllwed the mtin with their while nnperceivers fixated n the nn-mving element f the display.

5 Perceiving Adjacent Objects as Separate Perceptual Develpment 5 Xu and Carey (1994) habituated infants t a yellw ty duck sitting n tp f a red ty truck. Dishabituatin ccurred when they shwed a hand lifting the duck away frm the truck. This result suggests that they perceive the duck and truck as. Mdificatin f Experiment: Additin f Mvement When the duck mved back and frth n tp f the truck during habituatin the infants dishabituated t the. Indicating that helped them t see the duck and truck as 2 separate bjects. Clr Visin Perceptin f clr is determined by f cne receptrs. Cnes are. Research suggests that clr visin develps early and by 3 t 4 mnths is near adult levels. Depth Perceptin Depth perceptin requires the cmbinatin f many visual abilities. Infants are brn with depth perceptin, but this ability develps rapidly ver the first year f life. Mtin is the f depth cue t which infants are sensitive. Bincular Disparity becmes functinal early, but pictrial cues becme functinal later. Independent Mvement and Depth Perceptin Investigatrs have cncluded that is made pssible by independent lcmtin. Researchers believe that is s imprtant in structuring infants experience f the wrld, it may prmte a new level f by strengthening certain synaptic cnnectins in the crtex.

6 Perceptual Develpment 6 Visual Cliff Using Bincular Disparity One requirement fr bincular disparity is that the eyes must be able t bincularly fixate s that the tw fveas are directed t exactly the same place. Aslin (1977) filmed infant s eyes while mving a target back and frth frm distances f 12 cm t 57 cm. Nt until did bth eyes reliably mve tward the target. Bincular Fixatin is present at 3 ms, but can infants use the infrmatin frm disparity t perceive depth? Using Bincular Disparity Fx et al. (1980) Experiment Infants (2-6 mnths) wre special viewing glasses. Randm-dt steregrams were presented. Infants between three and six mnths f age Perceiving Mvement Infants prefer mving stimuli. At first infants track a mving bject using a series f shrt, jerky mvements called. At abut they are able t make smth eye mvements while tracking mving bjects. SUMMARY: VISION By 2 mnths, infants can discriminate clrs acrss the entire spectrum. By 3 mnths, infants can fcus n bjects and discriminate clrs abut as well as adults can. By 6 mnths, their visual acuity is abut 20/100. By 11 mnths, visual acuity reaches a near-adult level.

7 Perceptual Develpment 7 INFANT HEARING Newbrns prefer cmplex sunds such as vices. Newbrns are Newbrns prefer speech that is high-pitched and expressive In the secnd half f the first year, infants can detect in sentences. Between 7 and 9 mnths, infants have begun t analyze the internal structure f sentences and wrds. HEARING Fetuses respnd t sund nises affect brain wave patterns and heart rate. Decasper & Spence (1986): Dr. Seuss's "The Cat in the Hat Newbrns prefer mm s vice: Decasper & Fifer (1980): Perceiving Speech Categrical perceptin f phnemes - experiment by Eimas et al. One-mnth-ld infants are expsed t phnemes with different vice nset times (VOT). Habituatin respnses fr sucking n a nipple shw that VOTs f 20 ms (sunds like ba ) with changes t 40 ms (sunds like pa ). VOTs changed frm 60 t 80 ms (bth sund like pa ) shwed Cntrl grup with n changes in sund, shwed thrughut experiment. These results reveal the.

8 Perceptual Develpment 8 Speech Perceptin cntinued At birth, infants can distinguish between phnemes. By ne year f age, this ability becmes tuned s that An example is the distinctin between /r/ and /l/, which Japanese infants can distinguish at birth but nt at. OLFACTION Olfactin and Taste are the f all the senses at birth. The respnsiveness f infants t the smell f certain fds is. A newbrn infant is attracted t the dr f her wn mther s lactating breast. TASTE Infant facial expressins indicate they can distinguish amng several tastes, TOUCH Tuch helps stimulate physical and emtinal develpment. Sensitivity t tuch, pain, and temperature change is present at birth. Intermdal perceptin Intermdal Perceptin Recent evidence indicates that babies perceive the wrld in an intermdal fashin frm the beginning. Fr example, newbrn behavirs suggest that they expect sight, sund, and tuch t g tgether.