DICHOTIC-LISTENING IN CHILDREN - THE REFLECTION OF VERBAL AND ATTENTIONAL CHANGES WITH AGE

A sample of 290 kindergarten children (147 girls), all native Hebrew s peakers, were tested by two dichotic listening tests: (a) a digits tes t (low verbal workload) and (b) a words test (high verbal workload). T he same subjects were tested one year later (at the end of their first year at school) by the same tests. In both tests and both testing ses sions the free recall procedure was used. It was found that the perfor mance difference between ears significantly decreased and overall perf ormance significantly increased in the digits test in the second testi ng session. Differences between sessions in ear difference in the word s test were not significant, although overall performance in the secon d session increased. These data lend support to the hypothesis that th e change with age in the between-ears difference is mainly related to an improvement in verbal processing efficiency, which in turn allows t he allocation of more verbal resources to the inferior input channel, without a decrease in resources allocated to the preferred one. As exp ected, increase in available verbal resources was clearly manifested u nder low verbal workload conditions but not under high workload condit ions, where task demands did not allow significant increase in verbal resources to be allocated to the inferior channel. This hypothesis als o predicted highly consistent ear preference owing to its being solely determined by the verbal processors of the dominant-to-speech hemisph ere. The inconsistent ear preference between tests found in more than a third of the subjects of this sample could not therefore be accounte d for by the stated hypothesis. The analysis of performance in subject s who showed left-ear preference in only one rest and right-ear advant age on the other occasions indicated that whenever the left ear was pr eferred it was accompanied by significantly smaller ear difference and lower overall performance compared with those manifested by the same subjects in the same test in the other testing session. These data are better accounted for by the hypothesis that two different pools of re sources are involved in splitting attention between ears in the free r ecall of dichotically presented verbal stimuli: one which is controlle d by verbal processors of the dominant-to-speech hemisphere and the ot her by a spatial attentional mechanism. However, it seems that changes in dichotic test performance within the first year at school can main ly be attributed to increase in verbal resources rather than to improv ement in allocation of spatially controlled resources. (C) 1997 Academ ic Press.