An order effect in English infants’ discrimination of an Urdu affricate contrast

An order effect was found in English infants’ discrimination of an Urdu contrast. In Experiment 1 7- and 11-month-old English infants were tested on the Urdu contrast between the affricates /tʃʰ/ and /tʃ/. The order of presentation was counterbalanced: At each age half the infants were habituated to the aspirated and tested on the unaspirated affricate, the other half habituated to the unaspirated and tested on the aspirated. As expected, younger infants discriminated the contrast whereas older infants did not, showing the expected decline in discrimination. Interestingly, order of presentation seemed to affect the older infants’ response. Experiment 2 tested the order effect directly. The results showed no asymmetry in the performance of 7-month olds but clear asymmetry in that of 11-month-olds, who discriminated the contrast only when the non-English-like aspirated affricate was presented first. Experiment 3 tested adult native-speakers of both Urdu and English. Although the English listeners showed a reduced sensitivity to the contrast, there was no effect due to order of presentation of the stimuli in either adult group. The finding of an asymmetry in the infants suggests that infants’ perceptual narrowing for speech sounds may be a more complex phenomenon than has generally been assumed.