For some reason, the Powers that Be imagine you will be out shopping this Saturday, little comprehending that you have eschewed such conspicuous consumption for the pleasures of staying at home and reading about digit span. In one of Pliny the Younger’s letters (you will know the precise reference, dear reader) he writes an aside after one of his more philosophical reflections, saying that only he and the esteemed recipient of his missive would be interested in such things, since at the moment of writing the town was deserted because everyone was at the races. Such are the sacrifices and soul hardening consequences of disinterested intellectual curiosity.
At ISIR2014 Gilles Gignac wondered whether memory span was the ugly duckling of intellectual assessment. This is familiar ground to readers of this blog, so I will only summarise the main points.
Although memory span subtests have been included in well-known intellectual assessment batteries for over 100 years, these subtests have been (and continue to be) regarded as the worst indicators of cognitive ability. For example, Wechsler (1939; 1958) contented that beyond an absolute minimum, there were no
intellectual benefits to a greater memory span. By contrast, in the area of cognitive science, individual differences in memory span, and working memory in particular, have been regarded with great regard. In fact, working memory has been suggested to be the fundamental basis of intellectual functioning. In this talk, the large gap between these two positions will be attempted to be narrowed, based on the key results associated with three studies.
Method: The first and second studies were based on the WAIS-IV normative sample data (N = 2,200). The second study was based on archival data dating from 1923 to 2008 and amounted to a total approximate N = 7,000. In the first two investigations, the analyses consisted principally of a combination of linear and nonlinear bifactor modeling. The third investigation involved the plotting of Digit Span Forward and Digit Span Backward normative sample means across time.
Results and conclusions: Memory Span, as measured by Longest Digit Span Forward, Longest Digit Span Backward, and Longest Digit Span Sequencing, evidenced nearly average loadings on the general factor (g), suggesting that they are decent indicators of g. In the second investigation, the association between memory span and FSIQ (as well as g) was observed to be nearly completely linear, such that every extra level of memory span corresponded to an increase of approximately 4 FSIQ points. Finally, based on the archival investigation, both Digit Span Forward and Digit Span Backward test scores were found to be completely resistant to the Flynn Effect across 85 years of data.
Discussion: This is the first investigation to examine and demonstrate that all three memory span subtests within the WAIS-IV are moderately good indicators of g. Furthermore, the fact that the association between the three memory span measures and g is largely linear underscores their assessment value at all levels of ability. Finally, memory span test scores are possibly the only test scores not to evidence any susceptibility to the Flynn effect, again, highlighting their attractiveness as indicators of cognitive ability.
Conference News: another author has re-analysed the results, and comes to a somewhat different conclusion about Flynn effects. I am waiting for that paper to be accepted, and have forewarned Gignac that it is coming, in the hope of getting an advance copy of his eventual reply. You will be the first to hear the news, so long as you keep tuned to this channel.