Which Acoustic and Phonological Factors Shape Infants' Vowel Discrimination? Exploiting Natural Variation in InPhonDB.

A key research question in early language acquisition concerns

the development of infants’ ability to discriminate sounds, and

the factors structuring discrimination abilities. Vowel discrimination,

in particular, has been studied using a range of tasks, experimental

paradigms, and stimuli over the past 40 years, work

recently compiled in a meta-analysis. We use this meta-analysis

to assess whether there is statistical evidence for the following

factors affecting effect sizes across studies: (1) the order in

which the two vowel stimuli are presented; and (2) the distance

between the vowels, measured acoustically in terms of spectral

and quantity differences. The magnitude of effect sizes analysis

revealed order effects consistent with the Natural Referent

Vowels framework, with greater effect sizes when the second

vowel was more peripheral than the first. Additionally, we find

that spectral acoustic distinctiveness is a consistent predictor of

studies’ effect sizes, while temporal distinctiveness did not predict

effect size magnitude. None of these factors interacted significantly

with age. We discuss implications of these results for

language acquisition, and more generally developmental psychology,

research.

A key research question in early language acquisition concerns

the development of infants’ ability to discriminate sounds, and

the factors structuring discrimination abilities. Vowel discrimination,

in particular, has been studied using a range of tasks, experimental

paradigms, and stimuli over the past 40 years, work

recently compiled in a meta-analysis. We use this meta-analysis

to assess whether there is statistical evidence for the following

factors affecting effect sizes across studies: (1) the order in

which the two vowel stimuli are presented; and (2) the distance

between the vowels, measured acoustically in terms of spectral

and quantity differences. The magnitude of effect sizes analysis

revealed order effects consistent with the Natural Referent

Vowels framework, with greater effect sizes when the second

vowel was more peripheral than the first. Additionally, we find

that spectral acoustic distinctiveness is a consistent predictor of

studies’ effect sizes, while temporal distinctiveness did not predict

effect size magnitude. None of these factors interacted significantly

with age. We discuss implications of these results for

language acquisition, and more generally developmental psychology,

research.