Based on these forms of evidence, many researchers attempt to remove the influence of general processing speed from their dependent measures, in order to focus on contributions from other cognitive processes of interest. Moreover, age-related changes in processing speed appear to account for a substantial portion of age-related change across a wide variety of abilities ( Bryan & Luszcz, 1996 Cepeda, Kramer, & Gonzalez de Sather, 2001 Earles & Coon, 1994 Kail & Hall, 1994 Madden, 1992 Mendelson & Ricketts, 2001 Salthouse, 1991 Salthouse & Meinz, 1995). Processing speed predicts automaticity, fluency, and variability of cognitive performance across a wide variety of tasks ( Bryan & Luszcz, 2001 Finkel, Reynolds, McArdle, & Pederson, 2005 Kail & Salthouse, 1994 Salthouse, 2005). Individual differences in processing speed are believed to reflect variation in neural speed, efficiency, and capacity ( Birren & Fisher, 1995 Mendelson & Ricketts, 2001), as well as age-related changes in neural processing, including the development and decline of axonal myelination across the lifespan ( Charlton et al., 2006, 2008). People process information at different rates, and these differences appear to matter.
Implications for understanding processing speed, executive control, and their development are discussed. We find that the choice of processing speed measure affects the relationship observed between processing speed and executive control, in a manner that changes with age, and that choice of processing speed measure affects conclusions about development and the relationship among executive control measures. We report two new studies and a re-analysis of a published study, testing predictions about how different processing speed measures influence conclusions about executive control across the life span. This concern may apply particularly to studies of developmental change, as even seemingly simple processing speed measures may require executive processes to keep children and older adults on task. However, many commonly accepted measures of “processing speed” may require goal maintenance, manipulation of information in working memory, and decision-making, blurring the distinction between processing speed and executive control and resulting in overestimation of processing-speed contributions to cognition. The rate at which people process information appears to influence many aspects of cognition across the lifespan.
0 kommentar(er)
