Development of ear asymmetries in dichotic listening

Two hundred and eight Ss from grades 2, 4, and 6 were tested for recognition of dichotically presented musical stimuli, sound effects, and CVC nonsense syllables differing in medial vowel or initial stop consonant. Ear asymmetry was found to increase from grade 2 to grade 6. The left-ear advantage found for music, sound effects, and vowel-varied stimuli was due to decreasing right-ear performance with age. A right-ear advantage for consonants was the result of increasing right-ear performance and a simultaneous decrease in left-ear performance with age. These results were discussed in terms of a unilateral dominance specific for speech as opposed to a bilateral dominance for both speech and nonspeech material. Sex differences were found in the development of ear asymmetry, girls showing ear asymmetry earlier than boys in the recognition of verbal material and boys showing ear asymmetry earlier than girls in the recognition of sound effects. The results of the study were compared with those of a similar study using adults as Ss. The comparison showed that substantially larger ear asymmetries were obtained with grade 6 Ss than with adults. This difference was found to be due to the children's inferior recognition of stimuli presented to the nonpreferred ear, preferred ear performance being the same for both groups. The possibility of a covert order of report factor influencing the magnitude of the ear asymmetry found was suggested.Arts, Faculty ofPsychology, Department ofGraduat