Factors affecting the processing of intensity in school-aged children

Abstract

Purpose: Thresholds of school-aged children are elevated relative to those of adults for intensity discrimination and amplitude modulation (AM) detection. It is unclear how these findings are related or what role stimulus gating and dynamic envelope cues play in these results. Two experiments assessed the development of sensitivity to intensity increments in different stimulus contexts.

Method: Thresholds for detecting an increment in level were estimated for normal-hearing children (5- to 10-year-olds) and adults. Experiment 1 compared intensity discrimination for gated and continuous presentation of a 1-kHz tone, with a 65-dB-SPL standard level. Experiment 2 compared increment detection and 16-Hz AM detection introduced into a continuous 1-kHz tone, with either 35- or 75-dB-SPL standard levels.

Results: Children had higher thresholds than adults overall. All listeners were more sensitive to increments in the continuous than the gated stimulus and performed better at the 75- than at the 35-dB-SPL standard level. Both effects were comparable for children and adults. There was some evidence that children's AM detection was more adultlike than increment detection.

Conclusion: These results imply that memory for loudness across gated intervals is not responsible for children's poor performance but that multiple dynamic envelope cues may benefit children more than adults.

Figure 1

The distributions of thresholds for increment detection with a continuous standard (left panel) and intensity discrimination with a gated presentation (right panel) are shown for children and adults. Horizontal lines indicate the median thresholds, boxes delineate the 25^th – 75^th percentiles, vertical lines indicate the 10^th – 90^th percentiles, and circles indicate the minimum and maximum thresholds.

Figure 2

Thresholds for individual listeners are plotted as a function of age for child listeners. Mean thresholds for adult listeners are indicated at the right of the figure, with error bars showing +/− 1 standard deviation. Thresholds for gated stimuli are plotted with open circles, and those for continuous stimuli are plotted with filled circles, as indicated in the legend.

Figure 3

Following the convention of Figure 2, threshold estimates are plotted for individual listeners as a function of age for child listeners. Mean thresholds for adult listeners are indicated at the right of the figure, with error bars showing +/− 1 standard deviation. The top panel shows results of the increment detection, and the bottom panel shows results of the AM detection task. Symbols indicate stimulus level, either 75 dB SPL (filled, up-pointing triangles) or 35 dB SPL (open, down-pointing triangles).

Figure 4

Increment detection thresholds are plotted as a function of modulation detection thresholds for two signal levels. Symbols indicate stimulus level, which was either 75 dB SPL (filled, up-pointing triangles) or 35 dB SPL (open, down-pointing triangles). Adult data appear in the left panel, and child data appear in the right panel. The line fitted to adult data is indicated with solid lines in each panel. The best fit to child data is indicated in the right panel with a dotted line.