MOM 2006 journal for pdf.pmd - University of Michigan-Flint

Analysis of Variance
A 2x3 repeated measures analysis of variance (ANOVA) was conducted examining the effects
of the fluency task (verbal, categorical) and age group (young, y-old, o-old) on fluency scores.
As predicted, there was a significant main effect of fluency task, F (1, 134) =140.85, p < .001,
with the overall categorical fluency mean (M=16.81, SD= 3.95) higher than the verbal fluency
mean (M=12.89, SD = 4.02). There was also a significant main effect of age group, F (2, 134) =
6.84, p = .001. The old-old had fewer responses across both tasks than the young. The fluency
by age interaction was significant, F (2, 134) = 53.27, p < .001. A Bonferroni Post-Hoc analysis
was conducted, yielding a significant difference at p< .05 for old-old (M=14.65, SD = 3.09) and
the young (M=18.73, SD = 2.99) on category fluency; and for old-old and young-old (M = 17.16,
SD = 4.48) at p< .05 for category fluency (with a mean difference of 2.51). Post-hoc mean
differences for letter fluency were not significant.
Discussion
As predicted, all adults produced more responses to the category cue than they did to the initial
letter cue. These results replicate earlier findings that people find it easier to generate words for a
category than for an initial letter. In addition, old-old adults produced fewer category responses
than the young adults and the young-old adults. The age by task interaction obtained reveals that
older adults produced disproportionably fewer responses to the category cue than to the letter cue.
Even though this outcome is consistent with the more general Fourth Age Hypothesis (Baltes,
1997), it is not consistent with that proposed by the frontal lobe hypothesis.
Neuroanatomical Implications
Old-old adults produced disproportionably fewer responses for the category fluency task than for
the letter fluency task. This age by fluency interaction reveals that aging may affect category fluency
more than letter fluency. Because previous research suggests that category naming is associated
with the left temporal lobe, these results suggest that aging may result in more degeneration in the
temporal areas of the brain. Hence, these findings are not consistent with the Frontal Lobe Hypothesis.
It is also possible that age-related degenerative changes are similar across both regions but that
recruitment processes are more effective in the frontal lobes resulting in reduced behavioral outcomes
in those areas (Cabeza, 2002).
Cognitive Aging Implications
Our results highlight two aspects of cognitive aging. First, that precipitous declines may
characterize the population of adults older than 75 years of age, as described by Baltes (1997). At
present, research pertaining to the nature of and the extent of these declines in old-old adults is
scarce, so our results augment this hypothesis. In addition, our findings indicate that, as in adults
younger than 75, uniform decline across tasks may not be observed in adults older than 75 years of
age.
The second aspect of cognitive aging that is highlighted by these results pertains to the issue of
uniformity of age-related neuroanatomical or neurophysiological declines. Our data suggest that
temporal areas associated with category fluency may be particularly affected. These results are not
consistent with the frontal hypothesis, which proposes that the frontal lobes are affected more by
normal age-related degenerative processes.
Meeting of Minds 2006 20