Infants' Preference for Child-Directed Speech Over Time-Reversed Speech in On-Channel and Off-Channel Masking

Purpose: This study aims to examine the development of auditory selective attention to speech in noise by examining the ability of infants to prefer child-directed speech (CDS) over time-reversed speech (TRS) presented in "on-channel" and "off-channel" noise. Method: A total of 32 infants participated in the study. Sixteen typically developing infants were tested at 7 and 11 months of age using the central fixation procedure with CDS and TRS in two types of noise at +10 dB signal-to-noise ratio. One type of noise was an "on-channel" masker with a spectrum overlapping that of the CDS (energetic masking), and the second was an "off-channel" masker with frequencies that were outside the spectrum of the CDS (distractive masking). An additional group of sixteen 11-month-old infants were tested in quiet and served as controls for the "off-frequency" masker condition. Results: Infants preferred CDS over TRS in both age groups, but this preference was more pronounced with "off-channel" masker regardless of age. Also, older infants demonstrated longer looking time for the target stimuli when presented with an "off-channel" masker compared to the "on-channel" masker. Looking time in quiet was similar to looking time in the "off-channel" condition, and looking time for CDS was longer in quiet compared to the "on-channel" condition. Conclusions: These findings support the notion that (a) infants as young as 7 months of age are already showing preference for speech in noise, regardless of type of masker; (b) by 11 months of age, listening with the "off-channel" condition did not yield different results than in quiet. Thus, by 11 months of age, infants' cognitive-attentional abilities may be more developed.