Age-Related Impairment in Executive Functioning: Updating, Inhibition, Shifting, and Access

ABSTRACT

Miyake, Friedman, Emerson, Witzki, Howerter and Wager (2000) have argued that the central executive is fractionated consisting of at least three separable component processes: updating, shifting, and inhibition. The Wisconsin Card Sort Test, random letter generation, Brooks spatial sequences, reading and computation span, word fluency, and a measure of dual task performance were administered to 95 individuals aged between 20 and 81, average age 41.89. The executive measures were factor analyzed, using the oblique rotation method, yielding four factors. The factor structure obtained was broadly consistent with Miyake et al's. However, an additional factor, the only one not to show a significant performance decline with age, was also obtained and was believed to reflect the efficiency of access to long-term memory.

ACKNOWLEDGEMENTS

The authors are grateful to Peter Warr for his contribution during the early stages of this investigation and to Akira Miyake, Martial Van der Linden, Angela Nananidou, and two anonymous reviewers for comments on earlier versions of this manuscript.

Notes

¹ Miyake et al's random generation measures are based on equivalent indices developed by Towse and Neil (1998).

² This was achieved through a series of hierarchical regression analyses with the factor score as the dependent variable. Processing speed was entered in the first block of the analysis followed by age in the second block.

³ It is noteworthy that Byran et al's results were based on a large sample and that the age related variance in their initial letter fluency measure only amounted to 2.4% of the total variance.