Prelinguistic Development: Perception
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Hypotheses:
A. Infants are born with limited perceptual ability.
B. Infants are born with ability to perceive most and possibly all speech sounds.
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Methods
Sucking rate (below 0;6)
Heart rate (below 0;6)
Head turn (typically 0;6 and up)
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Habituation paradigm
Repetition leads to habituation
New stimulus leads to dishabituation (if perceived as different)
Selected Studies and Results
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Eimas, Siqueland, Jusczyk, & Vigorito (1971)
Infants: 26 at 0;1 26 at 0;4
Stimuli: [pa] (3 variants) vs. [ba] (3 variants)
VOT -20, 0, 20, 40, 60, 80 msec
Method: non-nutritive sucking rate
Result: Difference perceived
Conclusion:
Infants can make fine phonetic discriminations (universal theory)
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Eilers et al. (1979)
Infants: 8 Spanish & 8 English, 0;6-0;8
Stimuli: [pa] vs. [ba] English vs. Spanish
Method: Head turn
Results: Percent Correct Responses
English infants
Spanish infants
Sounds
English
Spanish
92%
42%
86%
80%
Conclusion:
Some sounds make be harder to perceive than others, I.e. infants may not be capable at birth
at perceiving all speech sounds
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Werker & Tees (1984)
Infants: English 0;6 to 1;0
Stimuli: Hindi dental vs. retroflex stops
Salish: [k’] vs. [q’]
Method: head turning
Results:
Age
0;6- 0;8
0;8 - 0;10
0;10 – 0;12
Percent Correct Responses
Hindi
Salish
95%
80%
68%
52%
20%
10%
Conclusion:
1. Support universal theory
2. Ability lost around 0;10 for non-native sounds
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Kuhl et al. (cf. Kuhl 2000, 2001)
– 1. infants detect patterns in input -> 2. exploit statistical properties of input -> 3.
perception altered (warped) by experience
– native language magnet (linguistic experience warps perception)
– prototypes (most typical exemplars of a category); prototypes are powerful anchors that
function as perceptual magnets to strengthen category cohesion
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Kuhl, 1991
– 4 experiments with 3 groups: English adults, English 6 to 7-month-olds, Rhesus monkeys
– look at % correct identification of stimulus change
Prototype
Non-prototype
EFFECT
Adults
78.6
90.5
yes
Infants
61.7
73.2
yes
Monkeys
69.2
71.5
no
Conclusions:
– monkeys not affected by categories
– prototypes are mentally represented
– typicality affects perception
– prototypes (centers) rather than fixed phoneme boundaries
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Kuhl et al, 1991
– synthesized /i/ and /y/; 32 Swedish and 32 English 6-month-olds
– conditioned head turn
– by 6 months, infants show stronger magnet effect for their native language prototypes (i.e.
English infants show magnet effect for /i/, and Swedish for /y/, but not for non-native
vowel)
• Summary of Other Results (Juszyk, 1997, 2001)
Infants perceive wide range of speech
(vowels & consonants)
Prefer their mother’s voice (birth)
Prefer their native language (birth)
Prefer their own names (4 ½ mos)
Detect familiar words in running speech (7 ½ mos)
Prefer frequent phonotactics (9 mos)
American English infants show preference for strong-weak (native) word stress at 9 months
(Jusczyk, Cutler, & Redanz, 1993)
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Perceptual Assimilation Model (Best)
We assimilate non-native sounds to those similar in the native language
E.g. Japanese speakers with English /r/ /l/
E.g. English speakers with Zulu clicks
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Phonological Deafness (Doupoux & Peperkamp)
Infants form prelexical representations around 1;0
Use them to perceive all speech
E.g. Japanese [ebzo] vs. [ebuzo]
Summary
Why are infants so good?
1. Aids phonological acquisition
2. Word segmentation (majority of words are typically not heard in isolation)
Excellent perceptual abilities from birth
Attuned to native language at around 1;0
Necessary for subsequent word acquisition
Phonological deafness