Background Background Background

Background

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

• 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

Anders Højen Center for Child Language Department of Language and Communication University of Southern Denmark

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Discrimination of Hindi and Salish by Englishlearning infants 6-8 mo. Discriminate contrasts in both languages 8-10 mo. Half of the infants could discriminate 10-12 mo. Few could discriminate (Werker, 1989)

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Discrimination of the English /r/-/l/ distinction: Sensitivity increases for American infants but decreases for Japanese infants between 6-12 mo. (Kuhl et al., 2006)

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Background

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Background

• 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

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Background

Background

• 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”:

• 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, 2003) and inter-modal preferential looking task or IPL (Swingley & Aslin,

– 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

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Background

Background

• Sensitivity to phonological detail of well-known words at 18-23 months (Swingley & Aslin, 2000) • “Recovery” of sensitivity to phonological detail of novel words at 17-20 months (Werker et al. 2002)

Hypothesis (Fennel & Werker, 2003) • Word-learning (novel) too computationally demanding at 14 mo. but not 20 mo. to encode words accurately • Word recognition (well-known) less demanding – can be done already at 14 mo.

14 mo. 20 mo.

Well-known

Novel

√ √

÷ √ 9

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Background

Background

• 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., 2000)

• More or less detail for vowels than consonants in early word representions? 11

• Conflicting results • 20-month-olds showed sensitivity mispronunciations in the consonant but not the vowel in novel words (Nazzi, 2005) • 15 to 24-month-olds sensitive to mispronunciations in both vowels and consonants in well-known words (Mani & Plunkett, 2007)

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This study

Methods

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

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

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Methods – Exp. 1

Methods – Exp. 1

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

Methods – Exp. 1 (Vowel target)

(Monitor) ”Sut”

”Kat” Change consonant

Change vowel

Kut

Table 1. Auditory stimuli, which were either correctly pronounced or mispronounced

Correct

Mispronunced

Danish

IPA

Enlish

sut kat bil ful

sut kt bil ful

“pacifier” “cat” “car” “bird”

sat kut bul fil

st kut bul fil

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Methods – Exp. 1

Example of MP trial (Consonant target)

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Procedure • Infant sits on parents lap in dim booth • On each trial, two pics shown for 5000 ms • At 2250 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: 1500 ms 18

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Methods – Exp. 1

Methods – Exp. 1

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 vowel target = vowels constrain lexical access more than consonants • 16 test trials (8 CP, 8 MP)

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Results – Exp. 1

Small positive difference score in MP trials (looking time a consonant target minus vowel target),

not signific. different from 0 Non-significant preference for consonant target

Δ looking time, ms

preference in CP trials

• Preference for target in CP trials = experiment works • Non-significant 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 20 months

500 400 300 200 100 0

Target minus Distractor

Cons. target minus vowel target

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Methods Exp. 2

Results – Exp. 2 Difference score (looking time at target minus distractor in MP trials) shows target

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

preference in CP trials Small negative difference score in MP trials (looking time a consonant target minus vowel target),

not signific. different from 0

– Consonant target: Kat-picture – Vowel target: Kop-picture 23

Non-significant preference for vowel target

600

Δ looking time, ms

Difference score (looking time at target minus distractor in MP trials) shows target

Discussion

500 400 300 200 100 0 -100 -200 -300

Target minus Distractor

Cons. target minus vowel target 24

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Discussion

Discussion

• Non-significant preference for vowel 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 words at 20 months

Interpretation problem • Lack of preference for either consonant or vowel target 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

– Supports Mani & Plunkett (2007)

2. Accept of kot as both “kat” and “kop” – vowels and consonants both phonologically underspecified 25

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Discussion

Discussion

Interpretation problem • Under specification of both vowels and consonants in well-known words at 20 mo. is unlikely

Final consonant vs. vowel

Initial consonant vs. vowel 500

600

400

Non-significant preference for cons. target

300 200 100

Δ looking time, ms

Δ looking time, ms

– evidence of substantial detail for vowels and consonants in English infants aged 14-15 mo. – if both vowel and final consonant are underspecified, it should be hard to tell kat from kop in CP trials

• Possible effect of position of mispronunciations 500 400

Non-significant preference for vowel target

300 200 100 0 -100 -200

• Convinced?

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Discussion

-300

Target minus Distractor

Cons. target minus vowel target

Target minus Distractor

Cons. target minus vowel target

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Discussion

• 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

• Could this effect solve interpretation problem? • If the effect of position of mispronunciation is significant, how could both vowels and consonants be underspecified?

– But they eventually discard MP forms resulting in lower looking times than in CP trials 29

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Conclusion

Thank you!

• Vowels and consonants do not differ in constraining lexical access to well-known words at 20 months • Suggests that vowels are as phonologically well-specified as consonants are in word representations at 20 months • Future: difference between vowels and consonant specificity at 14 months?

• Presentation will soon be available from – www.andershojen.dk – www.sdu.dk/cfb

• 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 – Widex A/S

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References

References

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Polka, L., & Werker, J. F. (1994). Developmental-Changes in Perception of Nonnative Vowel Contrasts. Journal of Experimental Psychology-Human Perception and Performance, 20(2), 421-435. 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. 92-127). 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(6640), 381-382. Swingley, D., & Aslin, R. N. (2000). Spoken word recognition and lexical representation in very young children. Cognition, 76(2), 147-166. Swingley, D., & Aslin, R. N. (2002). Lexical neighborhoods and the word-form representations of 14-month-olds. Psychological Science, 13(5), 480-484. Werker, J. F. (1989). Becoming a native listener. American Scientist, 77(1), 55-59. Werker, J. F., Fennel, C. T., Corcoran, K. M., & Stager, C. L. (2002). Infants’ ability to learn phonetically similar words: Effects of age and vocabulary size. Infancy, 3(1), 1-30. 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), 49-63.

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