Sebastián-Gallés, N. & Bosch, L. (2009) Developmental shift in the discrimination of vowel...
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Sebastián-Gallés, N. & Bosch, L. (2009) Developmental shift in the discrimination of vowel contrasts in bilingual infants: is the distributional account
Sebastin-Galls, N. & Bosch, L. (2009) Developmental shift
in the discrimination of vowel contrasts in bilingual infants: is
the distributional account all there is to it? PSYC 525 Ji Young
Kim Fall, 2010
Slide 2
Background A shift from language-general to language-specific
discrimination in 6-month-old infants. Discriminability reduced
around prototypical exemplars of native vowel categories, while
discrimination was still preserved for exemplars around
non-prototypical vowels Statistical account: through continuous
exposure to the native language and language-specific mapping
alters perception. Most studies address the question of perceptual
reorganization processes in groups of monolingual infants.
Slide 3
Bosch & Sebastin-Galls (2003) Catalan and Spanish mid front
vowels Catalan: /e/ and / / Spanish: /e/ Discrimination was
available by 4 months of age, but evidence of this capacity could
not be obtained at 8 months of age. However, 12-month-old bilingual
infants were eventually able to reach discrimination for this
specific vowel contrast. U-shaped pattern. Different developmental
time- course
Slide 4
Bosch & Sebastin-Galls (2003) contd Infants phonetic
analyses of the bilingual input might converge in a shared
perceptual space, common to both languages. Spanish /e/ falls in
between Catalan /e/-/ / and is used with much higher frequency than
the two Catalan vowels (around 30% in Spanish and 8% in Catalan)
Formation of a single extended category which temporarily masks the
discrimination of the Catalan pair of contrastive elements. Through
continued exposure to Catalan and Spanish, bilingual infants would
eventually form smaller subcategories within this broader mid-front
vowel space, thus reaching discrimination at a later age.
Slide 5
Burns, Yoshida, Hill & Werker (2007) English-French VOT
distinction of /ba/ and /pa/ The precise location of the boundary
differs in the two languages. English: short-lag [b a] vs. long-lag
[p h a] French: pre-voiced [ba] vs. short-lag [pa] The acquisition
of phonological categories in monolingual and bilingual infants was
equivalent. No U-shape pattern. Equivalent developmental time-
course
Slide 6
Bosch & Sebastin-Galls(2003) vs. Burns et al.(2007) Bruns
et al. (2007): Difference between the results could be explained in
terms of both frequency and distribution of the different speech
sounds. Spanish /e/ > Catalan /e/-/ / English /b/-/p/ = French
/b/-/p/ This would prevent the speech perception system of
bilinguals from aggregating /b/ and /p/ into a single
category.
Slide 7
Sebastin-Galls & Bosch (2009) Spanish and Catalan back
vowels /o/-/u/ Contrastive in both languages Distribution: low
density region between /o/ and /u/ categories Frequency: Spanish
(/o/>/u/) Catalan (/u/ >/o/. vowel reduction )
Slide 8
Hypothesis If frequency and distributional properties are the
only driving forces to build up phoneme categories, then
8-month-old Spanish-Catalan bilingual infants should not have had
any trouble in keeping the /o//u/ categories separate.
Slide 9
Experiment 1 Participants 24 monolingual and 24 bilingual 4-
and 8-month-old infants 12-month-old bilingual infants Criteria:
language(s) spoken by parents, estimate of the hours of daily
exposure to the language(s) Monolingual: at least 80% of daily
exposure to the family language (Catalan or Spanish) Bilingual:
range from 50%50% to 65%35% of daily exposure to Catalan and
Spanish
Slide 10
Procedures Discriminate the natural exemplars of the target
[doi] [dui] pseudo-words, which were recorded by six different
female speakers using a motherese style. Discrimination based on
perceptual normalization of highly variable word-shaped stimuli
Familiarization-preference procedure Familiarization phase (12
stimuli of same target word) Test phase (6 similar tokens+ 6 novel
tokens)
Slide 11
Image on the center monitor to capture the attention; as soon
as the infant began to look at it, this image disappeared and a
different image appeared on one of the two side monitors. When the
infant was looking in that direction, the presentation of the test
stimuli began and continued until its completion or until the
infant ceased to look for more than 2 consecutive seconds. Recorded
attentional responses and duration of infants visual fixation
Slide 12
Results All 4-month-old infants discriminated the contrast
(significantly longer attention times) Only monolingual
8-month-olds showed discrimination behavior Bilingual infants
regained discrimination behavior at 12 months of age U-shape
pattern
Slide 13
Experiment 2 Too perceptually demanding?? Less varied stimuli
2a. Reduced talker variability (2 speakers) 2b. Reduced complexity
of stimuli (monosyllabic/do/-/du/) produced by a single speaker
Results Even in these very restricted situations, bilingual
8-month- olds failed to show discrimination behavior.
Slide 14
Discussion If frequency and distributional properties are the
only driving forces to build up phoneme categories, then
8-month-old Spanish-Catalan bilingual infants should not have had
any trouble in keeping the /o//u/ categories separate. No. Other
variables need to be considered as well.
Slide 15
Future study Degree of lexical similarity of the languages of
exposure (cognate words with different pronunciation especially in
vowels) Type of phoneme contrast (different processing units)
Certain degree of overlap of maximum and minimumF1 and F2 values
for /o/ and /u/ in Spanish(no difficulties have been observed in
the monolingual group)
Slide 16
Role of socio-indexical factors (one parent-one language
strategy) Actual acoustic-phonetic properties of bilingual adult
productions (in some circumstances, bilinguals categories are
deflected away to maintain contrasts existing in their L1 and L2,
while in other situations bilinguals productions are a compromise
between L1 and L2 categories. (Flege, 1995)) Specific
characteristics of infant-directed speech (IDS) in bilingual
environments.