Prof. Greg Francis 7/7/081Perceptual developmentIIE 366: DevelopmentalPsychologyGreg FrancisLecture 11Chapter 5: Perceptual andMotor DevelopmentModule 5.1 Basic Sensory andPerceptual ProcessesChildren and Their Development, 4/e by Robert KailMethods of Testing InfantPerception1. PreferenceGive them two things to lookat.IF they spend more timelooking at one than theother (controlling for sideand random variation), itmeans two things:a. They can tell them apart(discriminate), AND…b. they like one more thanthe other.Methods of Testing InfantPerception2. HabituationAs infants look at something more, they becomeless likely to look at it, and to change respirationand heart rate. In other words, they prefernovelty (other things being equal).Taken as a sign of learningGood for measuring discriminationHearing speech Babies like perceived changes When the syllable changes babies suck more often ba, ba, …, pa, pa, pa, pa, pa,… Moreover, they hear things the way adults do you can change the pronunciation (timing) of ba and still hear itas ba babies hear it the same wayBAPATypical Habituation Results071421281 2 3 4 5Habituation TrialLength of Look (sec)mos 3mos 4mos 5mos 7mos 9Prof. Greg Francis 7/7/0823. Evoked potentials (or Event RelatedPotentials, ERP) Baby ERP4. High-amplitude suckingUsed to test operant conditioning(if press lever, get food; if study hard, get good grade)The challenge: what response, and what reinforcer?Response: sucking. Reinforcer: interesting sight or sound.Measure whether sucking increases in rate and/or intensity.Conditioning from about 3 months.Taste and Smell Sensitivity to taste and smell developsbefore birth. Newborns innately prefer sweet flavors. Infant sense of smell draws them to theirmothers. Infants are sensitive to the smell of breastmilk.Prof. Greg Francis 7/7/083Touch Infants explore the world orally for the firstfew months. From 4 months on, infants begin to rub,finger, probe, and bang objects. Increase in manual control facilitates visualexploration.Intermodal Perception Infants are able to combine information from two ormore senses. Very young infants link oral and visual experiences. As they get older, infants integrate visual and tactileexplorations. Infants at about 4 months can integrate speakingsounds with a picture of lips moving. An integral part of understanding speech» McGurk effect5.1 Hearing Infants hearwell, thoughnot quite asaccurately asadults Soundintensity isdefined indecibels5.1 Hearing Infants’ hearing is best for sounds that havepitches in the range of human speechSpeech sounds Speech sounds are an especially important stimulus They cover particular frequency ranges to which people arevery sensitiveProf. Greg Francis 7/7/084Hearing loss As people age, their threshold intensity for hearing tends togo up Usually this is because of exposure to loud soundsiPods Unfortunately, people now listen to quite loud sounds fairlyoften And they turn up the volume in environments with loudsurrounding soundsHearing loss Worse still,hearing losstends tocover therange offrequenciesthat includespeech No one “getsused” to anoisyenvironment,it means youare goingdeaf.Auditory location Infants use audition to identify the location of sound sources in theenvironment A sound source will hit the two ears at slightly different times andintensities The time differences are small, but they are enough for the auditorysystem to judge the left-right position of the sound source The speed of sound is around 340 m/s (it depends on air pressure,temperature, humidity,…)5.1 Seeing Acuity is given a ratio of numbers(e.g., 20/20) Numerator refers to the distance in feetfrom which a person can reliablydistinguish a pair of objects. The denominator is the distance fromwhich a person with standard VA wouldbe able to distinguish them. The metric equivalent is 6/6 vision Acuity is 20/200 to 20/400 at birthbut improves rapidlyDevelopment5.1: Seeing Month 1 Eyes follow moving objects, not always perfectly Preference for black and white objects (checkerboards) Month 2 Some coordinated fixation Awareness of red and yellow (still a preference for black andwhite) Month 3 Coordinated fixation Attention to red and yellow Interest in facesProf. Greg Francis 7/7/085Development5.1: Seeing Month 4 Interest in own hands (finger tracking) Acuity 20/200 to 20/300 Month 5 Smoother eye movements Shift gaze from near to far Month 6 Acuity 20/200 or better Smooth and coordinated eye movements Recognizes faces at 6 feetDevelopment5.1: Seeing Months 6-9 Near normal acuity Month 9-12 Smoother eye movements Shift gaze from near to far Year 1 Mild farsightedness Normal depth perception AccommodationWavelength of Light5.1: Seeing5.1 Seeing Cones in the retina ofthe eye detect color By 3 or 4 months,infants’ colorperception is similar toadults’ color perceptionadultsInfants (4-5months)Amblyopia “Lazy eye” Central vision fails to develop for one eye (the amblyopiceye) For lots of different reasons If untreated, the brain stops responding to the problemeye, which becomes effectively blind Infants and children sometimes make the problem worseby favoring the good eye over the bad Squinting, closing bad eyeAmblyopia Treatment Force infant or child to use the amblyopic eye Not always effectiveProf. Greg Francis 7/7/086Next time Complex perception and