In Western countries, scores on IQ tests have been rising for several decades – the Flynn effect, named after the political scientist James Flynn. Now Sallie Baxendale at the Institute of Neurology has provided evidence that a similar effect has occurred for the standardised memory tests that are used by clinical neuropsychologists, a finding with implications for the diagnosis of memory problems in contemporary patients.
Baxendale focused on the Adult Memory and Information Processing Battery (AMIPB) – ‘the most commonly used memory battery amongst clinical neuropsychologists in the UK’ – published in 1985, and its successor, the Brain Injury Rehabilitation Trust Memory and Information Processing Battery (BMIOB), published in 2007. The two tests feature different wording and design but they both make equivalent demands: learning and recalling lists of words, and learning and recalling abstract line drawings.
Baxendale compared the performance of the two participant samples that provided the original normative data (the ‘norms’) for the two tests. These are the healthy participants, spanning four age ranges, whose average performance provides the benchmark for assessing patients. The normative data for the AMIPB was provided in 1985, or thereabouts, by 184 British people aged 18 to 75; the normative data for the BMIPB was collected in 2007 or thereabouts from 300 British people aged 16 to 89.
On one hand, there was little evidence of any difference in average performance on verbal learning and recall between the 1985 and 2007 samples (the exceptions were verbal learning in the 31-45 years age range and verbal recall in the oldest age range, both of which were superior in the 2007 sample). By contrast, visual learning and recall were both superior in the 2007 sample compared with the 1985 sample, at all four age ranges: 16-30; 31-45; 46-60; and 61-75. This is consistent with the traditional Flynn effect, which is most pronounced for non-verbal intelligence tests.
Baxendale said her findings have implications for diagnosis because present-day patients may, pre-trauma or pre-illness, have had elevated non-verbal learning and recall scores in comparison to the old normative data. Therefore, such patients could be impaired relative to their own healthy baseline, and yet appear unaffected compared with the out-of-date normative data. ‘This may present a confound for neuropsychologists concerned with the lateralising and localising significance of memory test profiles,’ Baxendale said.
Baxendale, S. (2010). The Flynn effect and memory function. Journal of Clinical and Experimental Neuropsychology, 32 (7), 699-703 DOI: 10.1080/13803390903493515