Paul B. Baltes, Reinhold Kliegl

• Earlier testing-the-limits research on age differences in cognitive plasticity of a memory skill was extended by 18 additional assessment and training sessions to explore whether older adults were able to catch up with additional practice and improved training conditions. The focus was on the method of loci, which requires mental imagination to encode and retrieve lists of words from memory in serial order. Of the original 37 subjects, 35 (16 young, ranging from 20 to 30 years of age, and 19 older adults, ranging from 66 to 80 years of age) participated in the follow-up study. Older adults showed sizable performance deficits when compared with young adults and tested for limits of reserve capacity. The negative age difference was substantial, resistant to extensive practice, and applied to all subjects studied. The primary origin for this negative age difference may be a loss in the production and use of mental imagination for operations of the mind.