Development of infant ear asymmetries for speech and music

It is suggested that the quality or use of lefthemisphere phonetic memory may change between 2 and 3 months, and that the engagement of right-hemisphere specialized memory for musical timbre may precede that for left-hemispheric phoneticmemory.

Abstract

Groups of 2-, 3-, and 4-month olds were tested for dichotic ear differences in memory-based phonetic and music timbre discriminations. A right-ear advantage for speech and a left-ear advantage (LEA) for music were found in the 3- and 4-month-olds. However, the 2-month-olds showed only the music LEA, with no reliable evidence of memory-based speech discrimination by either hemisphere. Thus, the responses of all groups to speech contrasts were different from those to music contrasts, but the pattern of the response dichotomy in the youngest group deviated from that found in the older infants. It is suggested that the quality or use of lefthemisphere phonetic memory may change between 2 and 3 months, and that the engagement of right-hemisphere specialized memory for musical timbre may precede that for left-hemisphere phonetic memory. Several directions for future research are suggested to determine whether infant short-term memory asymmetries for speech and music are attributable to acoustic factors, to different modes or strategies in perception, or to structural and dynamic properties of natural sound sources.