Delayed Left Ear Accuracy during Childhood and Early Adolescence as Indicated by Roberts' Dichotic Word Listening Test

A total of 200 girls and boys between the ages of 6 years and 15 years were administered Roberts' Dichotic Word Listening Test. A statistically significant relatively abrupt and maintained increase in left ear accuracy was noted after 9 years of age (eta = .55). Except for a mild improvement after 6 to 7 years of age, comparable changes were not observed for the right ear. The magnitude of the effect was not significantly diminished even after covariance for verbal fluency and semantic categorization. These results are compatible with the observations that myelination of the cerebral commissures and electroencephalographic phase relations of the right hemisphere achieve near-adult characteristics after 9 years of age. Boys displayed less accuracy for dichotic word listening, particularly for the left ear, compared to the girls (eta = .20).