Directional Asymmetries in Vowel Perception of Adult Nonnative Listeners Do Not Change Over Time With Language...

Area of Science:

• Phonetics and Phonology
• Second Language Acquisition
• Auditory Perception

Background:

• The Natural Referent Vowel (NRV) framework posits that directional asymmetries in vowel perception are influenced by language experience.
• Previous research indicates that native language acquisition alters vowel perception, but the impact of adult second language learning remains less clear.

Purpose of the Study:

• To investigate whether language experience, specifically distributional training, can influence directional asymmetries in adult nonnative vowel perception.
• To test a key assumption of the Natural Referent Vowel framework regarding the malleability of perceptual asymmetries.

Main Methods:

• Analysis of data from Spanish participants categorizing Dutch vowels /aː/ and /ɑ/.
• Two categorization sessions were conducted: before and 12 months after vowel distributional training.
• Vowel categorization was assessed using the XAB task, measuring similarity judgments between sequential sounds.

Main Results:

• Prior to training, Spanish listeners showed a directional asymmetry, performing worse on peripheral-to-central vowel changes (/ɑ/ to /aː/), consistent with NRV predictions.
• This perceptual asymmetry persisted 12 months later, despite significant improvements in overall vowel categorization accuracy after training.

Conclusions:

• Improvements in adult nonnative vowel categorization accuracy are not attributable to the reduction of directional perceptual asymmetries.
• Directional asymmetries in vowel perception, while shaped by native language acquisition, may be resistant to nonnative language experiences in adulthood.