How do we recognize sounds? CREATEDATE 5/7/09 3:58 PM how do we recognize sounds? William James Called the sounds around children the ?blooming, buzzing confusion? Categorical perception Hearing phonemic boundaries between sounds as categorical, and hearing the sounds within the category as the same When we listen to sounds we do not listen to all the little different variations?but rather differences in categories of sounds and so we understand In adults Different languages have different sounds and different boundaries Ex: in English: there is a difference between /b/ and /v/, but in Spanish, it is one sound somewhere in between /b/ and /v/ Adults can only differentiate boundaries in their native language In infancy: Just like adults, infants are not distinguishing all contrasts equally Phonemic contrasts bust not contrasts within a single category Infant categorical perception = adult categorical perception But! Unlike adults, infants perceive all phonemic contrasts, even the ones in other languages Babies = sound-comprehending miracles Across all of the languages of the world, there are about 600 consonants and 200 vowels In each language, only about 40 phonemes Different languages place phonemic boundaries at different places, and young infants are capable of distinguishing all of these boundaries Ex. Canadian infants can distinguish Czech sounds that do not exist in English But?a child needs to zero in on the sounds of the native language! Language-specific listening From ?citizens of the world? to ?culture bound? listeners Between 6 and 12 months of age Prior to 6 months: babies can discriminate all the vowels in the world After 6 months: can start discriminating only the vowels of their own language Prior to 6 months: English born infants can discriminate sounds of Hindi and Salish, but after 12 months they can no longer discriminate these sounds Prior to 6 months, Japanese born infants can discriminate /r/ and /l/; after 12 months, can no long discriminate these sounds Roots of Categorical Perception Boundaries between categories are not accidental The auditory system is biologically predisposed to perceive sounds in a certain way Not just in humans! Chinchillas can tell the different between p and b as well Not just for speech sounds. Non-speech, environmental sounds are perceived categorically as well Sound systems in human languages have developed around these in-built discontinuities in how the auditory system parses sounds Distribution of sounds in the native language shapes infant?s perception of sounds Phonemically different sounds are produced clearly, with in-bewteen sounds produced very infrequently Sounds that do not contrast phonemically are not produced distinctly, and all the in-between variations are produced as well Eg. In Spanish b ad v are not different phonemes, and adult speakers produce all in-between variations of b and v Sounds that are distinguished in the native language stay ; sounds that are not distinguished in the native language (vary freely) go away Stages of Babbling Reflexive vocalizations ( 0-2 months) Crying, coughing, sneezing Determined by vocal psychology in infants Cooing and laughter (2-4 months) Sounds of content Usually made in the back of the mouth Vocal play (4-6 months) Experimental play with sounds Sounds become more consonant-like and vowel-like Repertoire is limited: velar consonants (g, k) early on, labials and alveolars later on (m n p b q) Loud vs. soft, high vs. low, sustained vowels Raspberries (bilabial trills) Canonical Babbling (6 months +) Sequence of vowels and consonants = true syllables Syllables have adult-like timing, and sound like attempt at words Sequences of same syllables (mamama) = reduplicated babbling; lasts until 12 months Not always communicative; first stage of speech production that distinguishes hearing and deaf infants Sequences of different syllables (magibu) = variegated babbling; predominates after 12 months Jargon State (10 months + ) Conversational babble or modulated babble Strings of syllables spoken with language-appropriate stress and intonation Often overlaps with early meaningful speech Shows grasps of suprasegmentals and of social nature of conversation In normally developing children, disappears by 2 yrs of age Speech Production Develops as a result of changes in: Physical growth and development: Growth of facial skeleton gives tongue more room; control over oral-facial muscles allows children to control sound production Nervous system maturation: About 6- 16 weeks, brain regions responsible for emotion develop (limbic system); at the same time, cooking and laughter develops. Areas of motor cortex develop?at the same time, babbling begins Experience: Infants hear the speech adults produce, and hear their own speech Role of Feedback People around the infant = external feedback Speech around the child reinforces appearance of certain sounds Infant herself= internal feedback Hearing oneself speak and comparing it to speech of others Reinforces learning Deaf children with learn sign language from parents (can compare their signs to signs of their parents), but not oral language (cannot compare their vocalizations to speech production of their parents) Relationship between babble and speech Speech develops from babble Meaningful speech and babble overlap for several months Sounds of babbling are universal until 6 months of age, independent of the language Most frequent are stops (p b t d k and g), nasals (n and m), glides (w and j) and fricatives (s and h) Missing are dental and interdental fricatives (v and th), affricates( Tf) and liquids (r and l) Babble turns into speech To Sum Up: Ability to discriminate all sound categories disappears around 6-12 months of age (onset of language-specific speech perception) Babbling progresses through stages of development and evolves into meaningful speech
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