Methods for Studying Infants

SECTION II Perceptual development ❖ Methods for studying infants ➢ What they can do ■ Display physiological responses ■ Look ● Preferential looking: children tend to look more at face-resembling images than random ones ● Head turn preference: listen to sound from speakers, know if they orient themselves towards it then they choose which one they prefer to orient themselves towards more often ● Habituation: present same stimulus until infant stops looking ● Violation of expectation ■ Suck ● High amplitude sucking: two different speakers and examine difference in amplitude of sucking when comparing sounds ➢ What perceptual abilities are innate? What’s the role of experience? ■ Basic story ● Prenatal development ● Postnatal tuning (tuned in for the things the organisms need to do) ■ Some perceptual abilities, preference presence at birth ● Some are biologically based, specified ● Some due to prenatal learning ■ Development involves changes in body, brain, and behavior ■ Perceptual narrowing in early development ■ Newborn sensory capabilities ● Vision is least well-developed sense ◆ Sensitive to brightness; can discriminate patterns, some colors; track motion ◆ Acuity poor, improves rapidly in first ½ year ● Hearing relatively well-developed ◆ Turn to sounds, can discriminate loudness, direction, frequency ◆ Responsive to speech, phonemic contrasts ❖ Development of visual perception ➢ Changes in body – in the eye ➢ Changes in brain ➢ Changes in behavior: how to look at faces and what to look at ➢ Movement is critical! ■ Visual scanning patterns ■ Motor development, including locomotion ➢ Different types of cues ■ Monocular ■ Binocular ■ Motion-based ❖ Depth perception: some forms present at birth, other later ➢ Monocular (1 eye) cues to depth: motion-based cues early, pictorial cues later ➢ Binocular (2 eyes) cues to depth: 4mos ❖ Tuning of visual perception ➢ Becomes more selective over first year, as a function of experience ➢ Face perception: experiences with faces of different species, races, ages ➢ Perceptual narrowing with experience: ■ 6 mo can discriminate novel monkey faces, 9 mo cannot ■ Infants habituated to target face ■ Then presented with novel & familiar faces ■ Recognition: looking preference for novel face over two 5s intervals ■ 4 racial groups ■ Results: ● White 3mo showed a preference for the novel face for all 4 racial groups ● White 9-mos showed preference for the novel face only for white faces ■ Perceptual narrowing: experience is needed to maintain perceptual discrimination abilities ❖ Auditory perception development ➢ Relatively well developed at birth ➢ Auditory learning in fetuses: at birth ■ Preference for… ● Mom’s voice ● Native language ● Familiar story ● Familiar music ➢ Auditory localization: present at birth (knowing where a sound is coming from ■ U shaped developmental trajectory (birth-5mo) ● Subcortical vs cortical processing ● Control of head movements, strength of neck ● Changes in head size Paper - dis/cont - Mechanisms of change - Valuing motor skills (look at slides) - Textbook: in chapter ___ - Lectures: in lecture ___ - Cite readings Perceptual and language development ❖ Categorical perception ➢ ➢ Tuning of auditory perception for speech ■ ➢ Tuning of auditory perception ■ ■ All in all, we agree when to separate sounds to categorize them ➢ High amplitude sucking paradigm: dishabituated → also agree when it’s a different letter ➢ Social context: infant directed speech (IDS) ■ Higher pitch, wider range of pitch, exaggerated intonation, etc. ■ Infants prefer IDS over Adult Directed Speech ■ Could it help infants learn to perceive speech ● Exaggerates difference between vowels → better speech perception ➢ Tuning of auditory perception: categorical perception of speech sounds ■ Social context may play a role (IDS) ■ Narrows with experience ● Early on, infants sensitive to many distinctions not used in the languages they hear ● With time, infants lose ability to distinguish contrasts not used in their languages ➢ Music ■ Discrimination of sounds of different pitches ● Measure: detect mis-tunings in scale ■ Infants trains with operant conditioning paradigm ● Visual reinforcer appeared above speaker when there was a mis-tuned note ● Measured head turns ■ Adults raised hand to indicate mis-tuned notes ■ Results: ability to detect mis-tuning narrows with experience ❖ Intersensory integration: integration of information from 2+ sensory systems