This study examined the threshold effect hypothesis of selective attention on the magnitude of the dichotic right-ear advantage (REA) with young children. We hypothesized that children, in contrast to adults, might find it more difficult to selectively attend to stimuli that were presented to the left side of space (ear) even with an increase in the time available to orient attention. Attention was manipulated by presenting a lateralized tone cue to the targeted ear at shorter (150, 450, and 750 msec) and longer (500, 1,250, and 2,000 msec) stimulus-onset asynchronies (SOAs). Previous work with adults demonstrated that the magnitude of the REA was attenuated when sufficient opportunity to orient attention to the left ear (LE) was available. In contrast, results of this study indicated that for children (M age = 8 years 7 months) the magnitude of the REA was not attenuated even when SOA to the LE was lengthened. Specifically, REAs obtained beyond 750-msec SOA (i.e., 1,250 and 2,000-msec SOA) were not substantially attenuated from that obtained at 450 to 500-msec SOA. By assessing shorter and longer SOAs, we demonstrated that young children were unable to maintain attention to the left side of space (i.e., LE) for more than a brief period of time. In essence, children lack flexibility in overcoming the attentional bias toward the right ear even when more time is available for processing of stimuli. This may be the result of incomplete development of one or more cortical regions in the brain associated with interhemispheric attentional processing capacity.Dichotic listening paradigms were quite successful in yielding perceptual asymmetries for language-based discriminations with normal as well as with clinical populations (see Bryden, 1988;Obrzut, 1988 for reviews). The dichotic listening task in-
