Effects of size of interval between items and noise level upon immediate recall

The effect upon immediate recall of the length of the interval between auditorily presented sequences of 7 digits was studied while holding the rate of presentation constant at 1 digit per 500 msec.Ss were 144 normal-hearing young adults. An Intermediate-interval condition was created with taped naturally-spoken digits clipped each to 220 msec (interdigit interval of 280 msec). Short- and Long-interval conditions were created by expanding and compressing such digits by 33% with an AmBiChron unit, resulting in digit/interval durations of 290/210 and 150/350 msec, respectively. Digits were presented at 1 of 3 levels of white noise (no noise, -2 db, -8 db S/N). Only at the highest noise level (-8 db) S/N) did recall differ in the 3 interval conditions: recall was best in the Intermediate-interval condition and worst in the Short-interval condition. Differences were due to errors in item recall rather than to errors in order recall. These findings are inconsistent with the model of the time course of perceptual coding for immediate recall proposed by Aaronson et al. (Percept. & Psychophys., 1971, 9, 338-344.