AGE-DIFFERENCES IN MEMORY-SPAN ERRORS - SPEED OR INHIBITORY MECHANISMS

This study investigated age differences in errors on the digit-span ta sk. Protocols of 119 men and women, aged 18-99 years, were scored for the occurrence of three types of errors derived from the speed-of-proc essing and inhibition-deficit frameworks: omission errors, intrusion e rrors, and transposition errors. The types of errors made on the digit -span task varied with span size. At larger span sizes, participants w ere more likely to omit digits or introduce nonstimulus digits than to transpose those in storage. No age differences in intrusion errors we re found, however, old-old women (75+ years) were significantly more l ikely than young (18-25 years) and old (60-70 years) adults of either sex to exhibit transposition errors. Consequently, old-old women were significantly less likely to exhibit omission errors. The results indi cate that the digit-span task may involve two parallel processes: digi t storage/recall and serial/position storage-recall. Age differences i n the serial-processing component, rather than in the digit storage/re call component, may be age sensitive. These results are discussed with in an inhibition-deficit framework of cognitive aging.