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Young infants' perception of lexical and functional categories
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Young Infants’ Perception of Lexical and Functional Categories Rushen Shi*, Janet Werker*, and James Morgan** *Dept. of Psychology, University of British Columbia, Vancouver, BC, V6T 124 Canada **Dept. of Cognitive & Linguistic Sciences, Brown University, Providence, RI 01912 To acquire the rules by which words are combined to form phrases and sentences, infants must first learn to assign words to grammatical categories such as nouns, prepositions, etc. Our studies are based on the assumption that infants initially derive the binary, superordinate lexical and functional categories from perceptual cues in the input. These two categories are present in all human languages, and recent work reveals similar distinctive acoustic and phonological cues across languages (Shi, Morgan & Allopenna, in press). We therefore proposed for the first study that there exists an innate mechanism leading to initial sensitivity to cues separating the two universal categories. In the first study sixteen newborns were tested using the High-Amplitude Sucking paradigm. Stimuli were multiple lexical and function word tokens randomly selected and sliced from natural infant-directed utterances of an English-speaking mother. After being habituated to a word set of one category, infants were tested on either words of the other category or new words from the same category. The results showed that although newborns detected the change of any wordlist (either different or the same category), their recovery was significantly greater to words of the different category. This evidence supports a predisposed sensitivity which may serve as an initial foundation for the formation of grammatical categories. In the second study we questioned whether infants by the age of six months have the fullblown ability to classify words into lexical and functional categories based on the cues in input speech. Further more, given the evidence that six-month-olds not only possess an emerging ability to attend to certain segmental and prosodic characteristics of their native language, but also are beginning to recognize some commonly occurring words in their daily life (Jusczyk, 1997), we expected that infants’ perception of lexical, but not function words might be influenced by familarity. Thirty-two six-month-old infants were tested in an Infant-Controlled Visual Fixation Habituation Procedure. The visual stimulus was a checkerboard. The linguistic stimuli were the same as those in the first study. After being habituated to a word set of one category, the infant was presented with new words from the same category in one trial (control) and words from the other category in another trial (experimental), in a fully counterbalanced design. The results showed a significant recovery in infant looking time when the word category switched, but not when the category remained the same. This suggests that by six months, infants are capable of categorizing lexical versus function words. Follow-up analyses revealed that the recovery in looking time to the category switch was only significant in the switch from function to lexical words. Infants did not show recovery to function words after being habituated to lexical words. We interpret this finding as suggesting that by 6 months of age infants prefer to listen to lexical words over function words. This is predictable from the existing evidence that lexical words are acoustically and phonologically more salient than function words, and compatible with the finding that infants at this age recognize some lexical words in the input. Taken together, our studies suggested that infants at birth show a predisposed sensitivity to the cues separating lexical and function words, and by six months they not only show the fullblown ability to categorize the two categories of words, but also a preference for the acoustically and phonologically more salient lexical words. These abilities may serve as the bases for computationally limited perceptual analyses in parsing input utterances, forming more complete and mature sets of grammatical categories, and building an initial lexicon.
Young Infants’ Perception of Lexical and Functional Categories Rushen Shi*, Janet Werker*, and James Morgan** *Dept. of Psychology, University of British Columbia, Vancouver, BC, V6T 124 Canada **Dept. of Cognitive & Linguistic Sciences, Brown University, Providence, RI 01912 To acquire the rules by which words are combined to form phrases and sentences, infants must first learn to assign words to grammatical categories such as nouns, prepositions, etc. Our studies are based on the assumption that infants initially derive the binary, superordinate lexical and functional categories from perceptual cues in the input. These two categories are present in all human languages, and recent work reveals similar distinctive acoustic and phonological cues across languages (Shi, Morgan & Allopenna, in press). We therefore proposed for the first study that there exists an innate mechanism leading to initial sensitivity to cues separating the two universal categories. In the first study sixteen newborns were tested using the High-Amplitude Sucking paradigm. Stimuli were multiple lexical and function word tokens randomly selected and sliced from natural infant-directed utterances of an English-speaking mother. After being habituated to a word set of one category, infants were tested on either words of the other category or new words from the same category. The results showed that although newborns detected the change of any wordlist (either different or the same category), their recovery was significantly greater to words of the different category. This evidence supports a predisposed sensitivity which may serve as an initial foundation for the formation of grammatical categories. In the second study we questioned whether infants by the age of six months have the fullblown ability to classify words into lexical and functional categories based on the cues in input speech. Further more, given the evidence that six-month-olds not only possess an emerging ability to attend to certain segmental and prosodic characteristics of their native language, but also are beginning to recognize some commonly occurring words in their daily life (Jusczyk, 1997), we expected that infants’ perception of lexical, but not function words might be influenced by familarity. Thirty-two six-month-old infants were tested in an Infant-Controlled Visual Fixation Habituation Procedure. The visual stimulus was a checkerboard. The linguistic stimuli were the same as those in the first study. After being habituated to a word set of one category, the infant was presented with new words from the same category in one trial (control) and words from the other category in another trial (experimental), in a fully counterbalanced design. The results showed a significant recovery in infant looking time when the word category switched, but not when the category remained the same. This suggests that by six months, infants are capable of categorizing lexical versus function words. Follow-up analyses revealed that the recovery in looking time to the category switch was only significant in the switch from function to lexical words. Infants did not show recovery to function words after being habituated to lexical words. We interpret this finding as suggesting that by 6 months of age infants prefer to listen to lexical words over function words. This is predictable from the existing evidence that lexical words are acoustically and phonologically more salient than function words, and compatible with the finding that infants at this age recognize some lexical words in the input. Taken together, our studies suggested that infants at birth show a predisposed sensitivity to the cues separating lexical and function words, and by six months they not only show the fullblown ability to categorize the two categories of words, but also a preference for the acoustically and phonologically more salient lexical words. These abilities may serve as the bases for computationally limited perceptual analyses in parsing input utterances, forming more complete and mature sets of grammatical categories, and building an initial lexicon.