Background. Background. Background. Phonological specificity of vowels and consonants in 20-month-olds word representations

Transcription

1 Phonological specificity of vowels and consonants in 2-month-olds word representations Anders Højen Center for Child Language Department of Language and Communication University of Southern Denmark Infants discriminate phonetic contrasts already before 4 months of age (e.g., Eimas, Siqueland, Jusczyk, & Vigorito, 1971). Discriminate both native and nonnative contrasts from the beginning Sensitivity to nonnative contrasts decline around 12 months (Werker & Tees, 1984) Sensitivity to native contrasts increases around 12 months 1 2 Discrimination of Hindi and Salish by Englishlearning infants 6-8 mo. Discriminate contrasts in both languages 8-1 mo. Half of the infants could discriminate 1-12 mo. Few could discriminate (Werker, 1989) Discrimination of the English /r/-/l/ distinction: Sensitivity increases for American infants but decreases for Japanese infants between 6-12 mo. (Kuhl et al., 26) 3 4 High capability of perceiving native phonetic distinctions at around 1 year At this time word learning begins Word learning requires encoding of sound for later recognition Expect infants to encode the sound pattern of words accurately because of their perceptual abilities at 1 year of age BUT an early report indicated that at around 1 year, infants confuse minimal pairs (Shvachkin, 1973) They could discriminate but could not associate the right word with a referent Access to phonetic detail hampered by word-object association? 5 6 1

2 The effect of word-object association on perception shown again later in habituation-switch task (Stager & Werker, 1997) 14-month-olds were taught novel words : very different word pair: Lif Neem minimal pair: Bih Dih In test phase, infants noticed word-object switch for Lif-Neem pair, but not Bih-Dih But infants could discriminate Bih-Dih Reduced phonological sensitivity at 14 mo. when associating words with objects? I.e., words phonologically underspecified? Only novel words Sensitivity to mispronunciations of wellknown words at 14 mo. shown with switch task (Fennel & Werker, 23) and inter-modal preferential looking task or IPL (Swingley & Aslin, 22) 7 8 Sensitivity to phonological detail of well-known words at months (Swingley & Aslin, 2) Recovery of sensitivity to phonological detail of novel words at 17-2 months (Werker et al. 22) Well-known Novel 14 mo. 2 mo. Hypothesis (Fennel & Werker, 23) Word-learning (novel) too computationally demanding at 14 mo. but not 2 mo. to encode words accurately Word recognition (well-known) less demanding can be done already at 14 mo. 9 1 The just-reviewed studies examined sensitivity to consonants But vowels might have either stronger or weaker representation than consonants Stronger: Vowel perception language specific sooner than consonants perception (Kuhl, 1991; Kuhl et al. 1992; Polka & Werker, 1994; but cf. Polka & Bohn, 1996) Weaker:Vowels constrain lexical access less than consonants in adults (Cutler et al., 2) More or less detail for vowels than consonants in early word representions? 11 Conflicting results 2-month-olds showed sensitivity mispronunciations in the consonant but not the vowel in novel words (Nazzi, 25) 15 to 24-month-olds sensitive to mispronunciations in both vowels and consonants in well-known words (Mani & Plunkett, 27) 12 2

3 This study Tested sensitivity to vowel and consonant mispronunciations in well-known words using IPL Purpose To pit sensitivity to vowel mispronunciations against consonant mispronunciations to determine if vowels constrain lexical access less than do consonants To examine sensitivity to consonant mispronunciations in the first vs. last consonant in CVC words 13 Methods Participants Thirty-two 19 to 21-month-olds 16 each in experiment 1 and 2 All were healthy full-term infants born to native speakers of Danish 14 Auditory stimuli Four correctly pronounced (CP) and four mispronounced (MP) Danish CVC MP words differed from the correct words in either the initial consonant or the vowel. Each MP stimulus could be reconstructed to two of the correct words by changing the vowel or initial consonant 15 Table 1. Auditory stimuli, which were either correctly pronounced or mispronounced Correct Mispronunced Danish IPA En lish sut kat bil fu l sat kut bul fil sut k t bi l fu l s t k ut bu l fi l pacifier cat car bird 16 Example of MP trial (Consonant target) Kat Change vowel (Monitor) Kut Change consonant (Vowel target) Sut 17 Procedure Infant sits on parents lap in dim booth On each trial, two pics shown for 5 ms At 225 ms, word stimulus (CP or MP) is presented in carrier sentence: Se, en Offline examination of picture fixation after word stimulus, frame by frame from video recordings (show video) Observation window: 15 ms 18 3

4 Procedure In CP trials, the picture named by the auditory stimulus was the target In MP trials, both pictures were possible targets. Auditory stimulus e.g., kut Consonant target: Kat-picture (correct consonant, wrong vowel) Vowel target: Sut-picture (correct vowel wrong consonant) Procedure Preference for looking at the consonant target in MP trials = consonants constrain lexical access more than vowels (weaker specification of vowels) Preference for looking at the = vowels constrain lexical access more than consonants 16 test trials (8 CP, 8 MP) 19 2 Results Exp. 1 Difference score (looking time at target distractor in MP trials) shows target preference in CP trials Small positive difference score in MP trials (looking time a consonant target ), not signific. different from preference for Preference for target in CP trials = experiment works preference for consonant target = no evidence that consonants and vowels differ in constraining lexical access Does not suggest a difference in specificity for vowels and consonants in well-known word representations at 2 months consonant target 22 Methods Exp. 2 Results Exp. 2 Examined sensitivity to mispronunciation in vowel vs. final consonant in CVC words Stimuli Four CP words and four MP words, analogous to experiment 1 stimuli Each MP stimulus could be reconstructed to two CP stimuli, e.g., Kot Consonant target: Kat-picture Vowel target: Kop-picture 23 Difference score (looking time at target distractor in MP trials) shows target preference in CP trials Small negative difference score in MP trials (looking time a consonant target ), not signific. different from preference for vowel target

5 preference for = no evidence that consonants and vowels differ in constraining lexical access Does not suggest a difference in specificity for vowels and consonants in well-known words at 2 months Supports Mani & Plunkett (27) 25 Interpretation problem Lack of preference for either consonant or upon hearing MP word, e.g., kot, could mean two things: 1. Rejection of kot as either kat or kop vowels and consonants both well-specified 2. Accept of kot as both kat and kop vowels and consonants both phonologically underspecified 26 Interpretation problem Under specification of both vowels and consonants in well-known words at 2 mo. is unlikely evidence of substantial detail for vowels and consonants in English infants aged mo. if both vowel and final consonant are underspecified, it should be hard to tell kat from kop in CP trials Convinced? 27 Possible effect of position of mispronunciations Initial consonant vs. vowel preference for cons. target Final consonant vs. vowel preference for 28 Suggests that infants process words from linearly, from one end If they hear kut, they look more for a picture whose name begins in /k/ (kat) than a name whose rhyme is right (sut) If they hear kot, they look more for kop than kat Hypothesis: lexical access constrained more by early sounds in words than late sounds But they eventually discard MP forms resulting in lower looking times than in CP trials Could this effect solve interpretation problem? If the effect of position of mispronunciation is significant, how could both vowels and consonants be underspecified?

6 Conclusion Vowels and consonants do not differ in constraining lexical access to well-known words at 2 months Suggests that vowels are as phonologically well-specified as consonants are in word representations at 2 months Future: difference between vowels and consonant specificity at 14 months? Thank you! Presentation will soon be available from These people contributed to the research: Thomas O. Madsen, Werner Vach, Torkil Østerbye, Karina Faber, Hans Basbøll, Sueli Caporali, Dorthe Bleses Research sponsored by University of Southern Denmark WidexA/S References Cutler, A., Sebastián-Gallés, N., Soler-Vilageliu, O., & van Ooijen, B. (2). Constraints of vowels and consonants on lexical selection: Cross-linguistic comparisons. Memory and Cognition, 28(5), Eimas, P. D., Siqueland, E. R., Jusczyk, P. W., & Vigorito, J. (1971). Speech perception in infants. Science, 171, Fennel, C. T., & Werker, J. F. (23). Early word learners' ability to access phonetic detail in well-known words. Language and Speech, 46(2/3), Kuhl, P. K. (1991). Human adults and human infants show a 'perceptual magnet effect' for the prototypes of speech categories, monkeys do not. Perception and Psychophysics, 5(2), Kuhl, P. K., Stevens, E., Hayashi, A., Deguchi, T., Kiritani, S., & Iverson, P. (26). Infants show a facilitation effect for native language phonetic perception between 6 and 12 months. Developmental Science, 9(2), F13-F21. Kuhl, P. K., Williams, K. A., Lacerda, F., Stevens, K. N., & Lindblom, B. (1992). Linguistic experience alters phonetic perception in infants by 6 months of age. Science, 255(544), Mani, N., & Plunkett, K. (27). Phonological specificity of vowels and consonants in early lexical representations. Journal of Memory and Language, 57, Nazzi, T. (25). Use of phonetic specificity during the acquisition of new words: differences between consonants and vowels. Cognition, 98, Polka, L., & Bohn, O.-S. (1996). A cross-language comparison of vowel perception in English-learning and German-learning infants. Journal of the Acoustical Society of America, (1), References Polka, L., & Werker, J. F. (1994). Developmental-Changes in Perception of Nonnative Vowel Contrasts. Journal of Experimental Psychology-Human Perception and Performance, 2(2), Shvachkin, N. K. (1973). The development of phonemic perception in early childhood. In C. A. Ferguson & D. I. Slobin (Eds.), Studies of child language development (pp ). New York: Holt, Rinehart & Winston. Stager, C. L., & Werker, J. F. (1997). Infants listen for more phonetic detail in speech perception than in word-learning tasks. Nature, 388(664), Swingley, D., & Aslin, R. N. (2). Spoken word recognition and lexical representation in very young children. Cognition, 76(2), Swingley, D., & Aslin, R. N. (22). Lexical neighborhoods and the word-form representations of 14-month-olds. Psychological Science, 13(5), Werker, J. F. (1989). Becoming a native listener. American Scientist, 77(1), Werker, J. F., Fennel, C. T., Corcoran, K. M., & Stager, C. L. (22). Infants ability to learn phonetically similar words: Effects of age and vocabulary size. Infancy, 3(1), 1-3. Werker, J. F., & Tees, R. C. (1984). Cross-language speech perception: Evidence for perceptual reorganization during the first year of life. Infant Behavior and Development, 7(1),