Discriminating languages by speech reading in adults and infants
Salvador Soto-Faraco, ICREA & Parc Ciencitífic de Barcelona, Universitat de Barcelona
We studied visual speech perception in adults and infants by exploring their ability to discriminate languages based on speech-reading. First, we tested adult observers with silent video-clips of an actor speaking in Spanish or Catalan using a 2AFC task. Our results established that Spanish-Catalan bilingual speakers could discriminate running speech from their two languages (Spanish and Catalan). However, we found that this ability was critically restricted by linguistic experience, as Italian and English speakers, who were unfamiliar with test languages, could not successfully discriminate the stimuli. In a further study, we used a preference looking paradigm to test whether young infants from English-speaking families could discriminate between English and French sentences. The results showed successful discrimination in 4 and 6-month-old infants just from viewing silently presented articulations. By 8 months, however, only bilingual (French/English) infants succeed. These findings are in accord with recent proposals arguing that the visual speech signal is rich in informational content, above and beyond what traditional accounts based on visemic confusion matrices would predict. In addition, they reveal a surprisingly early preparedness for extracting the relevant visual cues for language discrimination, and highlight selectivity in retaining only necessary perceptual sensitivities.
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