Search

A group of 5 normal hearing subjects were studied to determine their perception of the duration of auditory stimuli applied at constant frequency and intensity. In particular, their ability to discriminate between a pair of stimuli was measured. The minimum perceptible difference in duration was evaluated as the Weber fraction (WF) and was a function of the different stimuli duration (from 200 to 3200 ms) and the different interstimulus intervals (from 20 to 7200 ms). In addition, the interference stemming from two different attention conditions was also tested. The WF tended to increase for the 200,400 ms stimuli while it remained unchanged (at around 0.1) for higher durations. On the other hand, the WF was not affected by the inter-stimulus interval although it increased significantly according to attention interference. While these results confirm that estimates of auditory stimuli use attention controlled mechanisms they also suggest that information regarding duration is a stable perception temporarily residing in the short-term auditory memory and that it is not particularly susceptible to temporal decay.

A group of normally hearing subjects were exposed to tonal pattern in order to ascertain the influence that temporal characteristics of the stimulation may exert on short-term memory of pure tones. Four tones with different frequencies were used as stimuli (500 ms duration, 500 ms off) followed at intervals of 1 and 7 seconds by a probe tone. The subjects' task was to decide whether the sequence included the probe tone or not. The effects of the different duration of the four target tones, which, with regard to the total duration of the tones of the sequence were 12.5%, 25%, 37.5% and 50% respectively, were studied. The decrease in recognition performance relative to to the sequence/probe interval and to the ordinal position of the target, appeared to be governed by the proportionality of the duration of the target-tones. The ordinal position of the targets proved to be the factor which most influenced recognition performance. On the basis of these data, it may be hypothesized that a mechanism of attention, activated by the temporal characteristics of the tones in the sequence, improves the ability to store, recall and recognize target elements in multi-tone sequences.