Output loss or rehearsal loop? Output-time versus pronunciation-time limits in immediate recall for forgetting-matched materials.

Forgetting during recall may be one limit on memory span. Output time and accuracy of immediate serial recall using spoken and keypress responses were measured for digit, letter, and word sets approximately matched in phonemic discriminability and in immediate recognition memory. Nonetheless, the materials differed from one another in recall span, in output time during recall, and in pronunciation time (speech rate). Recall output times accounted precisely and completely for the measured memory span for these matched materials. Pronunciation times are correlated with recall output times, but output time gives a slightly better account of recall accuracy. The output time equivalent to the rule that short-term memory span corresponds to the number of items that can be said in about 1.5-2 s is that span corresponds to the number of items that can be recalled in about 4-6 s. Additional variations in span reflect differential item interference.