The development of auditory selective attention was assessed using event-related brain potentials (ERPs) and behavioral measures, with children (mean age = 8.1), adolescents (14.4), and young adults (23.8) as subjects. During separate blocks, subjects heard two sequences of pure tones (low- and high-pitched) or consonant-vowels (CVs; for example, ba vs da). Subjects were required to attend to one of the two stimuli in order to detect a deviant target embedded within the attended sequence, while ignoring the sequence comprised of the other stimulus (which also contained standard and deviant stimuli). The frequent standards were always 100 ms in duration, whereas the infrequent targets were of longer duration. The effect of selective attention was operationalized by computing the Nd difference waveform (ERP elicited by the unattended standard subtracted from that elicited by the attended standard). There was an increase in early Nd amplitude (measured from about 200 to 400 ms) and a decrease in its latency for both pure tones and CVs from childhood through young adulthood. For the amplitude measure, this effect was much more marked for CVs. Additional analyses indicated that the major effect of age involved reduction of negative-going ERP amplitude elicited by stimuli in the unattended channel, suggesting that with age there is an improvement in the narrowing of the attentional focus, with the major change taking the form of greater facility in rejecting stimuli in the unattended channel. Age-related shifts in scalp distribution of both early and late Nd were seen as consistent with, respectively, age-related changes in the way attention was allocated to the two input channels, and in the way in which the attentional trace was maintained by selective rehearsal.
