Julia Jones Huyck- j-huyck@northwestern.edu
Beverly A. Wright- b-wright@northwestern.edu
Northwestern University
Department of Communication Sciences and Disorders
2240 Campus Drive
Evanston , IL 60208-3550
Popular version of paper 3pPP8
Presented Wednesday afternoon, June 6, 2007
153rd ASA Meeting, Salt Lake City, UT
We most frequently think of time in terms of days or hours or minutes, but we are also strongly influenced by the duration of events that occur in tenths to hundredths of a second. In terms of hearing, for example, our sensitivity to time differences on this scale help us to distinguish one syllable from another (e.g., “ba” versus “pa”), enable us to detect meaningful pauses between words (e.g., “the black bird” versus “the blackbird”) and contribute to our sense of musical rhythm and tempo. However, despite the important role that such brief time differences play in daily life, little is known about how the ability to perceive differences in time periods on this scale changes through human development. Here we report that this ability continues to improve well into adolescence.
We tested groups of 11-year-olds, 14-year-olds, and adults (18-26 years) on their ability to discriminate differences in the duration of a silent interval between two short tones. On each trial, we presented, in random order, two tones separated by one tenth of a second and another two tones separated by a longer interval. The listeners indicated whether the longer interval came first or second. We adjusted the length of the longer interval from trial to trial in order to estimate the smallest time difference between the shorter and longer intervals that listeners needed to correctly discriminate between the intervals on 79% of trials. On average, 11-year-olds required a larger time difference to discriminate between the intervals and showed greater variability across repeated threshold estimates than did 14-year-olds, while 14-year-olds did not differ from adults. However, a sizable minority of 11-year-olds did demonstrate adult-like performance.
These results indicate that the neural mechanisms that encode auditory timing information on the scale of tenths to hundredths of a second continue to develop during adolescence, but that the exact time course of this development differs considerably across individuals. These data thus add to the emerging evidence that the development of many skills, including basic perceptual abilities, extends into the teenage years. They also suggest that performance on speech and music tasks that rely on the ability to discriminate brief time intervals may show a similarly long developmental course.
Press these buttons for examples of interval discrimination trials.
Example 1- 100 Millisecond Interval followed by 144-Millisecond Interval
Example 2- 100 Millisecond Interval followed by 122-Millisecond Interval
On each trial, we asked the listener to indicate whether the longer interval came first or second. In Example 1, the first interval between the two tones is 100 milliseconds (one tenth of a second) and the second interval is 144 milliseconds. This difference in interval duration reflects the average discrimination threshold for 11-year-olds on this task. In Example 2, the first interval is 100 milliseconds and the second is 122 milliseconds. This difference in interval duration is equal to the average threshold for 14-year-olds and adults.