Longitudinal study allowed researchers to disconfirm the controversial hypothesis of “dedifferentiation;” cognitive skill levels do not appear to merge late in life
Washington — Never good with numbers? The bad news: As you age, you may still not be good with them. The good news: You’ll still be good at what you’re good at today. New research reveals that, contrary to prior thinking, even the very old retain their distinctive patterns of cognitive strengths and weakness. The findings are published in the September issue of the Journal of Experimental Psychology: General, which is published by the American Psychological Association.
The results of a large-scale, longitudinal study did not confirm popular but unproven theories of “dedifferentiation” -– that for any given person, varied cognitive skill levels start to merge late in life, perhaps due to brain changes. Anstey and her co-authors explain that the dedifferentiation hypothesis –- that individuals “differentiate” cognitively as they mature into adulthood, and then “de-differentiate” as they enter old age — has a “long history in the fields of intelligence and individual differences, but has rarely been tested on a large, population-based sample of very old adults.”
In dedifferentiation, aging would make discrete cognitive abilities correlate more tightly with less of a spread between, say, verbal ability and memory, or processing speed and memory. It’s what would happen if students’ verbal and math scores were consistently closer on the GRE than on the earlier SAT. However, researchers were unable to confirm or disconfirm the theory, especially through longitudinal study – until now.
An Australian-American research team analyzed scores on various cognitive tests administered as part of the Australian Longitudinal Study of Ageing [sic]. The data came from 1,823 people grouped into cohorts of ages 70-74, 75-79 and 80-84 years old. A search of dozens of test correlations did not yield any signs of age-related dedifferentiation. For example, participants who, at age 72, were lower on verbal skills but higher on processing speed retained that difference at age 83. The analysis held up whether researchers studied people over time (longitudinal) or at a single point in time (cross-sectional), further supporting their claims.
Lead researcher Kaarin Anstey, Ph.D., and her co-authors say, “These results do not support the view that shared biological factors become increasingly important for explaining within-individual change in cognitive and sensory function late in life. It appears that in normal cognitive aging, people will maintain their relative strengths and weaknesses that they had earlier in life.”
Article: “Cross-Sectional and Longitudinal Patterns of Dedifferentiation in Late-Life Cognitive and Sensory Function: The Effects of Age, Ability, Attrition, and Occasion of Measurement,” Kaarin J. Anstey, Ph.D., Australian National University; Scott M. Hofer, Ph.D., Pennsylvania State University University Park Campus; and Mary A. Luszcz, Ph.D., Flinders University. Journal of Experimental Psychology: General, Vol. 132, No. 3.
(Full text of the article is available from the APA Public Affairs Office and http://www.apa.org/journals/xge/press_releases/september_2003/xge1323470.html).
Kaarin Anstey can be reached at the Centre for Mental Health Researcher, Australian National University, by email at firstname.lastname@example.org or by phone at 61-2-6125-8140.
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