M capacity as a lifespan construct: A study of its decrease in ageing subjects

The performance of 93 ageing subjects (age range, 59-96) was studied in tests that had been proved to measure M capacity in children (Morra, 1994), (i.e. the Backward Digit Span, the Counting Span, and the Mr Cucumber Test). For the sake of comparison, the Forward Digit Span was also administered. Preliminary analyses showed that Backward Digit Span, Counting Span, and Mr Cucumber have a similar rate of decline with age, and are significantly correlated with one another. The goodness of ” t of three different linear structural equation models suggests that, also in the elderly, the scores in these three tests reflect the same latent construct (i.e. M capacity), which in turn is negatively affected by age and positively affected by education. In addition, the variance within each subject of these three scores is usually small. It is concluded that these three tests can also be used as measures of M capacity in ageing subjects.