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Estimating the contribution of non-sensory factors to infant-adult differences in behavioral thresholds
1Department of Communication Sciences and Disorders, University of Georgia, Athens 30602-7152, USA. bnozza@moe.coe.uga.edu
Insights
Infant hearing thresholds are higher than adults. This study suggests auditory sensory factors account for 8 dB of the difference, while non-sensory factors explain the remaining 4 dB in infant hearing development.
Area of Science:
- Auditory perception
- Infant development
- Psychoacoustics
Background:
- Infants exhibit higher behavioral hearing thresholds than adults.
- Differences are attributed to auditory sensory and non-sensory factors.
- Previous research lacked direct estimation of these contributing factors.
Purpose of the Study:
- To estimate the relative contributions of sensory and non-sensory factors to infant-adult differences in hearing thresholds.
- To investigate auditory sensory differences in infants (8-11 months) compared to adults.
Main Methods:
- Determined behavioral thresholds for a 1 kHz tone in quiet and masking noise for infants and adults.
- Calculated the infant-adult difference in unmasked threshold.
- Estimated the infant-adult difference in minimum masking level (MML) as a proxy for sensory differences.
Main Results:
- The infant-adult difference in unmasked threshold was 12 dB.
- The infant-adult difference in MML was 8 dB at 1 kHz.
- Sensory factors accounted for an estimated 8 dB of the threshold difference.
Conclusions:
- Auditory sensory factors contribute significantly to infant-adult hearing threshold differences.
- Non-sensory factors account for approximately 4 dB of the observed difference.
- This study provides a quantitative estimation of sensory vs. non-sensory contributions to infant hearing.
Abstract:
Estimates of behavioral thresholds of infants are elevated relative to those of adults. Explanations for the differences include auditory sensory factors and non-sensory factors, but no direct estimates of the relative contributions of these two factors have been made. In this investigation, thresholds in quiet and in increasing levels of a masking noise for a 1 kHz tone, in infants 8 to 11 months old and in adults, were determined. The infant-adult differences in unmasked threshold was compared to the infant-adult difference in an estimate of the minimum masking level (MML) that was derived from the masking data. The intensity level of a masking noise at which masking begins is assumed to be independent of the non-sensory factors that impact on the threshold value itself. Therefore, it is reasoned that the infant-adult difference in MML reflects more closely differences in auditory sensory factors than does the infant-adult difference in unmasked threshold. In the region of 1 kHz, the infant-adult difference in behavioral threshold was 12 dB and the infant-adult difference in MML was 8 dB. Therefore, according to our assumptions, 8 dB of the infant-adult difference in unmasked threshold is accounted for by sensory factors and the remaining 4 dB must be attributable to non-sensory factors.