STABILITY AND EAR ADVANTAGE FOR DICHOTICALLY PRESENTED ENVIRONMENTAL SOUND STIMULI - DEVELOPMENT DURING EARLY-CHILDHOOD

55 right-handed children with no family history of left-handedness rec eived two dichotic presentations of environmental sounds. The mean tes t-retest interval was 9 days. Raw accuracy scores yielded acceptable t emporal stability (rs > .72). The expected consistent left-ear advanta ge for environmental sound stimuli was only evident in younger and les s mature children. Five- and 6-yr.-old children, particularly those wi th strong right-hand preferences, had a right-ear advantage for the st imuli. Their computed laterality coefficients showed low and nonsignif icant test-retest reliabilities, however. Three- and 4-yr.-old childre n, particularly those with weak hand preferences, had a left-ear advan tage for the same stimuli. Of the 3- and 4-yr.-old children who did no t have strong right-hand preferences, 92% demonstrated consistent ear advantages across testing sessions and their laterality coefficient te st-retest correlations were significant. In contrast, only 47% of the strongly right-handed 3- and 4-yr.-old children and 71% of the strongl y right-handed 5- and 6-yr.-old children had consistent ear advantages for the same stimuli. It is suggested that the 3- and 4-yr.-old child ren processed these stimuli according to endogeneous, stimulus-specifi c brain mechanisms and that learned processing strategies overrode the se mechanisms for the 5- and 6-yr.-old children.