A development study of auditory perception with special reference to right hemisphere functioning

Abstract

The traditional view that the left and right hemisphere is responsible for attending to verbal and sensory material is explored in a developmental study which ranges in age from 4.5 years to 18 years. Experiments on boys and girls used verbal material of increasing difficulty ranging from a random collection, statistical approximations to English prose and normal selections of English prose. The sensory material was composed of edited versions of 4 Seashore tests of Musical appreciation. White noise was used as a competing signal. Assessment shows that there is a significant advantage for the left ear to attend to pitch sounds. This advantage is maintained throughout all age groups, and both sexes, and is irrespective of ear order and dominance. In contrast the Loudness test, discriminating decibel levels, shows a right ear advantage, irrespective of the ear order. However left handers show a left ear advantage. The reasons for this sensory test (Loudness) to behave as a verbal test are discussed. The significant factor determining the experimental results is found to be the "ear presented first". This means that when the tests are presented to the right ear first there is a right ear advantage; when the tests are presented to the left ear first there is a left ear advantage. This ear order is interpreted at the physiological and psychological level. Extreme attention is required for auditory asymmetry to operate and the competing signal of white noise used in the experiments may not simula te a dichotic situation which would produce the difference between ears effects.The hypothesis that there is increasing lateralisation of function with age is not supported. The experiments reported here highlight the complexity of defining auditory stimuli as material specific. It seems important to break up sound into its essential elements, irrespective of whether it is cued by the human voice or an instrument, before discussion can be made with respect to the hemispheric level at which it is perceived.