DEVELOPMENT OF AUDITORY INFORMATION INTEGRATION ABILITIES

The ability of normal-hearing children (aged 4 through 7 years) and ad ults to integrate information was measured in an auditory sample discr imination task. On each trial a pair of tonal sequences was played who se component frequencies were randomly drawn from two equal-variance, Gaussian distributions with different means. The listeners task was to identify the sequence drawn from the distribution with the higher mea n frequency. Performance was first evaluated as a function of the numb er of components in each sequence. Results showed that discrimination accuracy improved with increasing age until age 7, at which time perfo rmance was adult-like. The 7-year-olds and the adults discriminated th e sequences with increasing accuracy as the sequence length was increa sed, but the 4- to 6-year-old listeners, as a group, did not. Data wer e fitted with a model with two free parameters, one representing resol ution of the components and presumed to reflect peripheral processing, and another representing central noise added to the decision process after the component information is combined [R. Lutfi, J. Acoust. Soc. Am. 86, 934-944 (1989)]. On average, both parameters showed gradual c hanges as age increased, with adult-like values by 7 years of age. Ind ividual data however suggest that the changes in central noise with ag e may be less gradual than the changes in peripheral resolution. In a second condition, increases in component duration produced improved pe rformance for the 7-year-olds and the adults, while that of the younge r listeners remained the same. Fitted parameters suggested improvement s in component resolution for the older children, with no changes in c entral noise levels. In a third condition, reducing the overlap in the distributions improved performance for only a few of several younger children. This improvement was attributable to lower levels of central noise. Overall, these results suggest that with increasing age childr en are better able to discriminate between sounds that are variable an d have overlapping acoustic characteristics. This age-related improvem ent may be attributed both to improvements in the ability to resolve t he components and to reductions in central noise. (C) 1996 Acoustical Society of America.