[Auditory memory and multi-tone sequences: effects of proportionality of tone duration]

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.