Boundary of steady state synthetic vowels (I) and (ε) in adults and school-age children

The purpose of this study was to investigate the categorical perception skills of typically developing school-age children and adults using synthetic vowels [i] and [ε]. Participants included ten adults, ten 5- to 6-year-old children, and ten 10-year-old children. Participants listened to 14 variants for tokens on a continuum between [i] and [ε] presented 10 times each for a total of 140 test trials. Upon presentation of each stimulus, participants were asked to choose between the two vowels Percentage of each token identified as [i] was calculated for each of the 14 variants for each subject The boundary, location of the 50% response point, was identified and steepness of the slope at the boundary was calculated. Comparisons of variance for each measure were made among groups. No significant difference in boundary was found among groups. However, a significant difference in slope at the boundary was found between the younger children and adults. A general trend was noted that slope at the boundary got steeper as age progressed. These findings support previous reports (e g, Walley & Flege, 1999) suggesting that categorical perception skills become more efficient as children mature.