Auditory development in complex tasks of comodulation masking release.

Experiments on listeners aged 5 years to adult were conducted to investigate the development of comodulation masking release (CMR) under conditions where auditory grouping could be affected either by the coherence of modulation pattern among noise bonds, or the temporal asynchrony among bands. The conditions examining CMR when two modulation patterns were present (each carried by a different set of noise bands) indicated a similar effect across all age groups. Here, CMR was substantial when the on-signal band (OSB) and six comodulated flanking bands (FBs) were presented, decreased when two bands having a second pattern of modulation were added, and then recovered partially when a further six bands that had the second modulation pattern were added. In conditions where there was a temporal asynchrony between the OSB and the FBs, the children typically showed smaller CMRs than the adults. In the case where the OSB preceded the FBs, adults typically showed CMR near zero when the temporal fringe was 50 ms or more. Children usually showed negative CMRs for such conditions. In the case where the FBs preceded the OSB, all age groups showed substantial CMRs, but the CMRs of adults were significantly larger than those of the children. The present results indicate that the effect of a second, independent modulation pattern on CMR is similar in children and adult listeners, but that CMR appears to be detrimentally affected more in children than in adults when there is a temporal asynchrony between the on-signal and flanking bands.