The role of acoustic/perceptual salience in directional asymmetry in infant stop/fricative contrast perception

The presence of stops in a language implicates the presence of fricatives but the reverse is unattested. Similarly, infants’ producing fricatives implies that they acquired stops. The privileged status of stops influences infants’ stop/fricative perception. For example, Altvater-Mackensen and Fikkert (2010) reported that Dutch-learning 14-month-olds noticed a fricative to stop change but not vice versa. These findings were interpreted in terms of phonological specifications while dismissing acoustic/perceptual factors. In this study, we assessed whether pre-linguistic infants show perceptual asymmetry. We tested English and French 4–5-month-olds using the look-while-listen procedure in which they were presented native nonsense syllables - /bas/ and /vas/. A mixed ANOVA showed a significant interaction between trial type and group (p = 0.027). Infants in /vas/-habituated group noticed the switch when the habituated fricative changed to a stop but infants in /bas/-habituated group did not notice the switch when the habituated stop changed to a fricative. This perceptual asymmetry in infants before babbling and word recognition stage indicates the potential role of acoustic/perceptual factors. We suggest that the above-mentioned privileged status of stops may reflect the possibility that stops are acoustically/perceptually more salient than fricatives. This salience difference is predicted to induce directional asymmetry in stop/fricative contrast perception.