What infants bring to language acquisition Limitations of Motherese & First steps in Word Learning

Newport, Gleitman, & Gleitman, 1977 Asked how important motherese is to language acquisition, particularly syntax Can it “teach” language to a child? Followed 15 dyads over a 6 month period Time 1: Structural complexity of maternal speech Times 1 and 2: Syntactic complexity of child speech Calculated “growth score” for each child Adjusted for child’s initial language level

Main Findings & Conclusions Modest correlations, but……. Children seem to have their own perceptual & linguistic filters that lead them to look for specific things in the input Motherese effective when it matches those this age listen for utterance initial items & items presented in referentially obvious situations –E.g. deixis, “THERE’s the ball” So, argues motherese is helpful, but only insofar as it complements the infants’ processing biases (Fernald would say, it helped those biases reach that point)

What processing biases do infants have for early word learning? Two papers this week, more next week This week –Word Segmentation (Jusczyk) –Categorization (Balaban & Waxman)

Word Segmentation In writing, blank spaces between words, but not in speech Once you know words, you can hear them But how do babies pull them out? Only some in isolation!

What have babies learned by months? Phonetic categories (position specific!) Phonotactics (consonant sequences allowed) Stress patterns Ability to use distributional information –A particular word in different contexts might pop out, e.g. –“the milk”, “drink your milk”, “do you want some milk” Can babies use these to help segment words?

How to test word segmentation Present babies with words in isolation over and over Test to see if they show a preference for listening to sentences with those words in them over sentences with other words in them

The Headturn Preference Procedure

Steps in HPP Familiarization phase: –Red light flashes on one side –Infant turns to look –Word is presented 15 times, or until baby looks away for at least 2 sec –Green light flashes at center to get attention –Then a red light on one side flashes again, and the other word is presented (varies randomly with side) –Continues until infant accumulates at least 30 sec of listening to each word

Steps in HPP (cont) Test Phase –Stimuli include 4 passages, each containing 6 presentations of a word –2 of the passages each contain a familiar word (e.g. “dog”, “feet”) –The other 2 passages contain unfamiliar words (e.g. “bike”, “cat”) –Procedure same as familarization phase, but measured how long infants listened to passages with familiar words vs. those with new words Results: –Infants > 7.5 months listen longer to passages with familiar words

Word Segmentation At 7.5 months only segment SW words Succeed on words like DOCtor and HAMlet But fail on words like guiTAR and deVICE For WS words, seem to pull out only the strong syllable Indeed, if the Strong syllable is always followed by a particular function word, will consider it part of the word E.g. pulled out “TAR is”

By months they get it right By 10 months, they can even segment WS words (e.g. “guiTAR”) Looks like at 7-8 months infants use: – the native language stress pattern – sentence level distributional information By months also use –position specific phonetic cues –Phonotactics N,G, & G would predict that motherese that accentuates the appropriate information at each age would be most effective

Do words facilitate categorization? To learn word meanings, infants need to pull out words But they also need to pull out the objects, events, etc. in the world those words refer to You learned last term that first words often refer to object categories How does this process get started? Baldwin has shown that words increase infant attention to visual displays & objects

Balaban & Waxman, 1997: Do words facilitate object categorization? How did B& W test this? Basic paradigm: –Showed exemplars from one object vs. another, accompanied most of the time either by A word (e.g. pig) A tone –Tested infants of 9 months, prior to the age at which they are easily learning actual words as labels

Balaban & Waxman (Cont). –Following this exposure, showed a novel exemplar of that category (a new pig) vs. an instance of the other category (a rabbit) –Measured looking time to the instance of the new category vs. the new instance of the old category Infants as young as 9 months showed marginally longer looking to the novel category in the word, but not the tone condition Conclude, that words do facilitate learning of object categories This could help prepare the child for later attaching labels to those object categories

What has this set of studies helped you understand about how infants might break into language? How could what you learned from the two papers you read this week help us understand how developmental changes in infancy help prepare the child for word learning? Could motherese teach a child to use words to categorize objects? Even if the answer is “no”, could motherese nonetheless complement this process?