Do bilingual babies learn when pitch changes a word's meaning sooner?
At about one year old, babies learning both English and Mandarin already treated a change in tone as changing a word's meaning in Mandarin but not in English, whereas babies learning only Mandarin did not show this until about 18 months.
Source
Limits on Monolingualism? A Comparison of Monolingual and Bilingual Infants' Abilities to Integrate Lexical Tone in Novel Word Learning
Study at a glance
- Design
- Human experiment — Four infant looking-time experiments using the Switch word-learning paradigm (habituate to a word-object pairing, then test with tone-changed labels) plus a tone discrimination habituation task; groups compared by language background and age.
- N
- No single N: four separate groups of 18 infants each - bilingual English-Mandarin 12-13-month-olds (Experiment 1), Mandarin monolingual 12-13-month-olds in word learning (Experiment 2) and tone discrimination (Experiment 3), and Mandarin monolingual 17-18-month-olds (Experiment 4).
- Population
- Healthy full-term infants in Singapore: English-Mandarin bilinguals and Mandarin monolinguals aged 12-13 or 17-18 months
- Outcome
- Looking time to Same versus Switch (tone-changed) test trials as an index of whether tone was treated as changing word meaning; looking-time recovery to alternating tones for discrimination
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What they did
Infants saw a moving novel object paired with the word 'pa' spoken in Mandarin Tone 3 until they got bored (habituated), then heard the same object named with Tone 1 (a distinct change) or Tone 2 (a similar change). Longer looking to the changed label was taken to mean the infant treated tone as part of the word. Bilingual 12-13-month-olds did this in both a Mandarin and an English naming context; Mandarin monolinguals were tested at 12-13 months and again, in a new group, at 17-18 months. A separate group of 12-13-month-old monolinguals completed a simple tone discrimination task.
What they found
Bilingual 12-13-month-olds looked longer when the tone changed in the Mandarin context (for both distinct and similar changes, more for distinct) but not reliably in the English context, showing language-selective use of tone. Mandarin monolinguals of the same age showed no reliable reaction to tone changes in word learning, even though another group of them could clearly discriminate the same tones in a non-word task. By 17-18 months, Mandarin monolinguals did notice both similar and distinct tone changes when learning new words.
The limits
What it doesn't show
Each group had only 18 infants, and bilinguals and monolinguals were different children, so background differences between the groups cannot be ruled out. The discrimination task in Experiment 3 used a different paradigm from the word-learning task, so it is not a perfectly matched comparison, as the authors note. All tests used a single syllable and Tone 3 as the base, which is the most complex and late-acquired Mandarin tone, so the monolingual delay might be specific to these stimuli. The explanations for the bilingual advantage (better cognitive control, metalinguistic awareness from cross-language conflict, or heightened pitch sensitivity) were proposed but not tested.
Key terms
- Lexical tone
- Pitch patterns that change a word's meaning, as in Mandarin, where the same syllable spoken with different tones is a different word.
- Phonological conflict
- When a sound feature matters for meaning in one of a bilingual's languages but not in the other, as with pitch in Mandarin versus English.
- Switch paradigm
- An infant word-learning task: babies habituate to a word-object pairing, then longer looking when the word is changed shows they noticed the pairing was violated.
- Habituation
- The decline in looking as a stimulus becomes familiar; renewed looking to a change (dishabituation) shows the infant detects a difference.
- Word learning paradox
- The finding that infants can hear the difference between two sounds yet fail to use that difference when learning new words.
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Quiz yourself
What did bilingual 12-13-month-olds show in the English naming context?
Common questions
Does this mean bilingualism confuses babies less than people think?
For this particular skill, yes: bilinguals were ahead of monolinguals in knowing when pitch matters for word meaning, despite facing conflicting rules in their two languages. It does not show a general bilingual advantage for all aspects of language.
Why weren't Mandarin-only babies sensitive to tone if they hear it all the time?
They could hear the tone differences, but in Mandarin pitch also signals questions, emphasis and emotion, so figuring out which pitch changes alter word meaning may take longer. The authors also suggest Tone 3, which was the base tone, may be especially hard for young learners.
How do researchers know what a baby 'thinks' a word means?
They measure looking time. After babies get used to one label for an object, they look longer if the label changes in a way they treat as meaningful, signalling surprise at a mismatch.
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