Developmental change in perception of clause boundaries by 6- and 10-month-old Japanese infants

Investigates whether Japanese infants are sensitive to acoustic cues of clausal units in Japanese speech. Groups of 6- and 10-month-old infants were tested using the headturn preference procedure (HPP). Two types of speech samples (child-directed speech) were examined: “coincident” samples were created by inserting one-second pauses at all clause boundary locations, and “non-coincident” samples were created by inserting the same number of pauses between words within clauses. Preferences were determined by assessing the listening times for each of 12 samples (6 of each type). For the 6-month-old infants, there was no difference in the listening times between the two stimulus types. For the 10-month-old infants, however, the listening time for the “non-coincident” samples was significantly longer than that for the “coincident” samples. These results indicate that Japanese clauses are not perceptual units for very young infants, but Japanese infants come to be sensible to the clausal units by 10 months old