Language Development: From Speech Perception to First Words PDF

Module 7 Chapter 11: Language Development: From Speech Perception to First Words infants acquire, on average, 9 new words a day after they hit about 50 words at 18 months To learn a new language, infants must: ○ Discover the salient sounds and auditory units of their language (phonology) ○ Learn the...

Module 7 Chapter 11: Language Development: From Speech Perception to First Words infants acquire, on average, 9 new words a day after they hit about 50 words at 18 months To learn a new language, infants must: ○ Discover the salient sounds and auditory units of their language (phonology) ○ Learn the meaning for words (semantics) ○ Learn the rules for how words and diff word forms can be combined to express new meanings (grammar) ○ To do all these, infants can use pragmatics = their understanding of how communication works and subtle nonverbal cues that parents use to aid communication ○ Infants use perceptual skills not specific to language (generalization, categorization) ○ Acquisition of knowledge aids acquisition of further knowledge (learning one part of language helps to learn the next) ○ Infants move from being universal perceivers (equally capable of learning any language) -> specialists in their own native tongue -> language-learning sophisticates, capable of producing some words they havent even heard yet The Universal Baby: Birth-6 Months The first 6 months infants move from being universal perceivers to perceiving the sounds of speech, recognizing melodies of their native language, communicating with those around them, and making first connections between sight and sound Early Production and Social Skills Newborns move from reflexive responses -> intentional vocalizations in a few months (cooing, vowel sounds, raspberries, lip smacking) -> vowel and consonant combinations Hearing newborns will respond to sounds with eye blinks or crying, or turn head in direction of sounds ○ 2 months: make eye contact with speakers Behaviours may encourage caregivers to communicate more with them ○ Emotional info from speech may motivate infants to attend to speech, encourages language acquisition All aspects of infant development interrelate! Early Speech Perception Newborns can differentiate between many sounds that distinguish words across all the words languages (even if subtle) Phonemic contrast = the meaningful diffs between vocal sounds ○ Ex. the phonemic difference between “b” and “p” Categorical perception: ○ adults discriminate between “b” and “p” when vocal onset time falls across diff categories (20 ms vs 40 ms VOT) but not in the same category (0 ms vs 20 ms VOT) ○ Infants demonstrated the same thing when tested! Infants can discriminate across many sounds that adults in their culture cannot = universal language perceivers These abilities are shaped to fit the languages theyre exposed to Suckling tasks show newborns can discrimminate between their native vs foreign languages Newborn discrimination happens when rhythm and intonational properties (prosody) of the languages differ largely ○ They can even discriminate when speech removes all info expect the prosody of it ○ Prosody is the very thing they can hear in the womb; suggests they become sensitive to mother’s speech and native language in the womb! 6 months: infants can recognize well-formed phrases or sentences, and prefer sentences with proper pauses at the end instead of sentences with weird pauses in the middle ○ Early sensitivities to prosody might help with learning grammar! Multimodal Perception Acquiring language involves connecting what one sees to what one hears ○ 2 month olds have demonstrated the ability to relate the sounds of diff vowels to the appropriate articulation of the mouth ○ Integration of info from multiple sensory modalities! 6 months: infants are starting to connect common words with their meanings Preferential looking paradigm: infants prefer to look at a video of their mother when they hear the word “mother” and same for fathers Do they know what “mother” and “father” mean broadly, or do they just know what it means in their PERSONAL context?? More advanced referential word knowledge (knowing words can refer to objects) comes at a later age Universal Baby Summary There are incredible perceptual abilities that develop even before birth ○ Infants can detect subtle speech properties that distinguish words, acquire prosody knowledge, link speech sounds to facial movements, and learn names of some common objects in their world Native Language Specialist: 6-12 Months Production and Developing Social Skills 6-7 months: canonical/reduplicated babbling ○ Reflect constraints of the vocal apparatus? ○ Consonants and vowels that involve the same articulation of the mouth usually co-occur Both hearing and deaf infants babble with their hands, but deaf babbling resembles sign language more than their vocal babbling 11 months: variegated babbling appears to be influenced by the language infants are exposed to Infants become more sensitive to emotional expression in voices and faces and become more expressing themselves Begin showing an understanding of referential gestures (ex. 9 month olds will look at the object the finger is pointing at, 6 month olds will look at the finger) Shaping of the Perceptual System 10-12 months: infants have lost the ability to discriminate sounds that arent relevant to their native language Perceptual assimilation model (PAM): suggests that sensitivity to non-native contrasts depends on whether and how the two speech sounds are categorized into native-language perceptual categories ○ Same perceptual categories = no discrimination, diff perceptual categories = discrimination ○ If they fall into no native categories = still discrimination, but less so ○ Infants that havent formed these perceptual categories of sound are more likely to discriminate than adults Perhaps the distribution of input to infants causes them to develop a perceptual weighting scheme = differences in sounds that arent relative to their immediate environment/native language become unimportant for perception Perhaps infants’ speech sound categories are influenced by the most common phonemes they hear ○ Infants are less likely to discriminate between a prototypical and non-prototypical sound than two non-prototypical sounds, even if the two pairs are acoustically and equally dissimilar Computations of the Ambient Language Infants appear to learn language based on what regularities they pick up in speech spontaneously rather than what they're explicitly taught ○ “Statistical learners” = they encode speech sounds and compute how often sounds and sequences occur Head turning procedure: 9-month-olds preferred two-syllable words with a more stressed first syllable (which are more common in the English language); 9-month-olds also more likely to turn heads towards non-words made of phoneme sequences that are more common in their native languages than those that are not (even if the phonemes alone WERE common) 6-9 months: infants become sensitive to the frequency of the occurrence of syllable stress and phoneme orderings in the ambient language by implicit computations of the sounds they hear “Transitional probabilities” of syllables: the transitional probability of XY = the probability that syllable X will follow the syllable Y ex. if the infants name is “Julie”, they learn the transitional probability that /Ju/ will follow /lie/ is almost 1.00 In one study infants would orient longer towards 0.33 transitional probabilities than 1.00, suggesting they had learned something 8 months: infants have learned to implicitly encode “statistical” info about speech Segmenting Words from Fluent Speech Infant directed speech flows continuously with no clearly marked word boundaries ○ Infants have to learn to segment words in fluent speech in order to learn their meanings Sensitivity to the properties of the ambient language plays a big role in this 7.5 month olds have been shown to do this in head turn studies English learning 7.5 month olds arent able to segment ALL words from fluent speech, but can segment those that follow the predominant stress pattern of english language (emphasis on the first syllable) 8-11 month olds rely more on these stress cues to infer word boundaries than on statistical cues Sensitivity to the rhythms of their languages helps them segment words from fluent speech Understanding Labels Close to 12 months, infants understand diff labels refer to diff objects ○ In a violation of expectancies paradigm they are surprised if both “dog” and “ball” are mentioned and they are only shown one object ○ 8-9 month olds know that two diff labels refer to two diff objects, rather than two identical objects ○ 9 month olds expect one label to refer to objects with similar functions, and two diff labels to refer to two diff objects with diff functions Latter portion of the first year = infants understand a single label refers to objects that look the same AND have similar functions Language Specialist Summary 6-12 months: infants become more engaged with caregiver, show a desire to communicate using language ○ They start to produce sounds that sound increasingly more like the language theyre hearing ○ Theyre encoding language statistics into memory, suggesting theyre attending to the speech around them ○ These skills converge to segment words from fluent speech to then subsequently help the infant understand word meanings Language Learning Sophisticate: 12-18 Months “Vacuum cleaners”: children acquire up to 9 new words per day Infants begin to use words meaningfully to communicate something Social Pragmatic Understanding Children have a “naming insight”: they ask, “whats that?”, using language to talk about the world and get what they want Infants follow pointing and eye gaze reliably, and wont mislabel something the experimenter didnt intend to label ○ Their ability to follow these cues is correlated with later linguistic competence Social Eye Gaze ○ Infant begin to follow eye gaze successfully ○ In one experimenter, 100% of 11-14 month olds would spontaneously look in the same direction as the experimenter; this ability can be used to learn labels ○ Intermodal preferential looking procedure: experimenter would label boring object -> 12 and 19 month olds would resist labeling the more interesting object, understanding the speaker was talking about the boring object 12 month olds would successfully label the “boring” object that the experimenter had been looking at Sensitvity to Referential Intent ○ Infants use referential other cues, such as an adult shaking their head no when looking for an object and finding the wrong object, to label an object ○ A study found that infants wouldn't misapply a label heard over a baby monitor while they were looking at an object ○ They understand when NOT to learn a label Understanding social pragmatic intent is the primary skill that infants need to learn language and sets humans apart from animals Other Constraints on Word Learning Whole-Object Bias: ○ Infants assume that novel words highlight the whole object rather than its smaller parts They prefer a novel object in a static display when asked to find a novel word over an attractive display representing an event Lexical Contrast: ○ Young children compare new words to the words they already know ○ Mutual exclusivity: infants know they can exclude objects that already have labels as possible candidates for new labels Ex. if a child’s mother says “look! An apple and a mango!” and they already know what an apple is, its much easier for them to learn what a mango is Categorical Induction ○ After learning some words, infants begin to guess how words might be extended to other similar objects They may categorize based on shape, substance, or something else Grammatical Understanding Recognizing parts of speech: ○ Syntactic bootstrapping: infants use grammar to discover possible meaning, even if the words are nonsense (they can guess which nonsense word might be a verb, noun, etc) Words preceded by a, an, or the are assumed to name objects, where adjective endings are assumed to label properties In one study where purple was described as “blickish”, infants labeled other purple objects “blickish” Sensitivity to morphology (diff forms that words take) show some aspects of grammar are being understood Understanding Word Order: ○ Infants are beginning to understand syntax (how words combine to make meaning) Ex. 19 month olds would look at the correct photo for “see big bird bending cookie monster” vs “see big bird and cookie monster bending” Question comprehension: ○ 15-20 months: infants know a bit about how questions work Looked longer at the apple when asked “what hit the flower?” and longer at the flower when asked “what did the apple hit?” The Wug Test ○ Some 18 month olds can produce new word forms that correspond to the rules of their native languages “This is the wug. There is another wug. There are two…” and the child would say “Wugs”.