Changes in Intellect with Age: I. Longitudinal Study of Wechsler-Bellevue Scores

Evidence for Aging as the Cause of Alzheimer's Disease

Part 1 presents the results of a meta-analytic study on the effects of aging on intelligence. Analysis of a total of 20 longitudinal samples shows that most of the intelligence scores rose before the age of 50 and fell at a progressively increasing rate after the age of 50. An equation describing this rise and fall in intelligence was derived. Part 2 shows the relationship between the predicted prevalence of Alzheimer's disease (from the equation derived in Part 1) and the prevalence of the disease obtained from 10 studies. The predictive curve fit so well with the observed prevalence data that the results can be interpreted as evidence that Alzheimer's is a manifestation of aging.

WAIS-R test-retest reliability in a normal elderly sample

We examined the 1-year test-retest reliability of WAIS-R Verbal, Performance, and Full-Scale IQs in a sample of 101 older normal individuals (mean age = 67.1). The respective Pearson rs were .86, .85, and .90. The median retest reliability coefficient for the WAIS-R subtests was .71. The test-retest reliability for the Verbal-Performance Discrepancy was .69. These data indicate that IQ scores are reliable in older normal individuals for this retest interval, but less confidence can be placed in the reliability of subtest scores and the Verbal-Performance Discrepancy.

Some important methodological issues in the study of aging and cognition

Despite extensive geropsychological research into cognitive change with advanced age, there is conflicting evidence regarding the nature of this change and even well developed arguments that no decrement with advanced age exists. A review of the field suggests that researchers have neglected certain important parameters which might greatly affect results Specifically, the following topics are examined: (1) determination as to what constitutes "young" and "old", (2) the source of the subjects in aging research, (3) methods of matching subject groups and (4) considerations of group heterogeneity. It was concluded that these issues are often confounded within research designs, that controlling them would help clarify theoretical issues, and that these parameters, when controlled, are themselves worthy of interest.

Psychologic and behavioral assessment of geriatric patients: a review

A review of the literature and a study conducted at a state hospital indicated that valid psychologic test results on geriatric patients are often difficult to obtain. Reasons most frequently offered by psychometricians for inconclusive or incomplete findings were the patient's uncooperativeness, unavailability, or severity of physical/mental dysfunction. A need was apparent for alternate assessment instruments for measuring current and potential levels of functioning in the elderly. In the investigation, attention was focused on the following areas: 1) studies in which the more traditional measurements were used, 2) articles stressing the need for caution in using the traditional techniques, and 3) studies in which behavioral rating scales and checklists were used as the evaluative devices. A large number of checklists and behavioral rating scales were found to be relevant and applicable to an institutional setting. Five were selected and are reviewed in depth.

Factor Analytic Studies Of Human Brain Damage: I. First And Second-Order Factors And Their Brain Correlates

This report is concerned with identifying the first and second-order cognitive factors underlying a battery of 49 measures taken from 22 brain damage tests. The test scores from 176 brain damaged patients between 16 and 65 years of age were intercorrelated and subjected to first-order alpha factoring followed by promax rotation to oblique simple structure. Ten of the 13 first-order factors extracted were interpretable, six of them being perceptual in nature and four being of a more conceptual nature. The perceptual factors include: perceptual organization, perceptual-motor speed, pattern recognition, temporal resolution, spatial orientation, and figure-ground identification. The conceptual factors include verbal comprehension, memory, and two abstraction factors. A second-order alpha factoring was performed on the matrix of correlations among the 13 primaries. Three of the five second-order factors extracted were interpretable. They were identified as perceptual integration (subsuming the first-order factors of perceptual organization, perceptual-motor speed, and temporal resolution), verbal memory (subsuming verbal comprehension and memory), and visualization (subsuming spatial orientation and figure-ground identification). Although factor interpretations were based primarily on the patterns of high loading variables, they were also influenced by lesion effects observed in this and related studies. About half the interpretable factors are relatively localized (i.e., confined to one or two lobes of one hemisphere), with the other half more diffuse (i.e., multi-lobed, combined with laterality or bilaterality). The more localized factors include the right hemisphere factors of perceptual-motor speed, temporal resolution, and spatial orientation, and the left hemisphere factors of verbal comprehension, memory, and verbal memory. The more neurally diffuse factors include the second-order factors and such broad gauged first-order factors as abstraction I and II, and pattern recognition. Furthermore, same lobe, bilaterally hemispheric effects were rare, and only four factors (memory, verbal memory, visualization, and abstraction I) were correlated with sub-cortical lesions.

The terminal drop hypothesis: fact or artifact?

Findings from eight longitudinal investigations were reviewed in order to evaluate the terminal drop hypothesis. The concept of terminal drop was seen to be more useful when partitioned into its component parts: the relationship between the level of cognitive performance with survival and with distance from death, and the relationship between changes in cognitive performance and death. Health status and age at death emerged as important intervening variables in understanding the terminal drop concept.