The evidence of this study shows that absolute size of memory span varies from material to material. The order of materials in terms of increasing difficulty in remembering is as follows: digits, consonants and colors (the latter two of about equal difficulty), concrete words, geometrical designs, and abstract words (the latter three of about equal difficulty), paired associates, nonsense syllables, memory for commissions, and sentences. A statistical analysis of the data suggests the conclusion that all of the tests call for a common ability, thus tending to keep the position of the individual constant in relation to the rest of the group, but also that certain abilities are called for in some of the tests and not in others, thus tending to make the position of the individual fluctuate in relation to the rest of the group. A factorial analysis of intercorrelations of the tests tends to bear out this conclusion. (PsycINFO Database Record (c) 2006 APA, all rights reserved)