Interspeech'2005 - Eurospeech
The use of duration as a perceptual cue in Dutch /A-a:/ is studied in children aged 5 and 7, and adults. Usually, Dutch listeners use both vowel duration and spectral composition as perceptual cues for /A/ and /a:/, but they can use duration alone. Despite the vowel contrast's salience, five-year-olds do not yet use duration as adults: half of them did not use duration at all. The seven-year-olds did not differ from the adults, implying that the use of duration as a single cue is acquired before age 7, but mostly after age 5.
Bibliographic reference. Heeren, Willemijn (2005): "Perceptual development of the duration cue in dutch /a-a:/", In INTERSPEECH-2005, 745-748.