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Patrick Rabbitt

Publications and source records attributed to Patrick Rabbitt.

9 recordsLinked to original sources
PubMed2006

Losses in gross brain volume and cerebral blood flow account for age-related differences in speed but not in fluid intelligence.

Age-related gross head size; adjusted age-related change in brain volume and carotid and basilar blood flow; as well as scores on 3 tests of fluid intelligence (gf), 2 tests of information-processing speed, 2 memory tests, and 3 tests of executive function were obtained from 69 volunteers aged from 62 to 84 years. Brain volume negatively predicted scores on all 10 cognitive tasks, accounting for up to 78% of age-related variance in scores on the speed tasks and on 1 executive task. Cerebral blood flow (CBF) negatively predicted scores on 8 cognitive tasks, accounting for up to 36% of age-related variance in speed scores. However, neither brain volume nor CBF accounted for significant age-related variance between individuals on any of 3 gf tests. We conclude that speed, but not gf, is an exceptionally sensitive behavioral index of the progress of gross brain changes that affect cognition in old age and that speed and gf do not reflect integrity of the same functional systems.

Aged↗
PubMed2005

Cognitive performance inconsistency: intraindividual change and variability.

Although many studies have examined inconsistency of cognitive performance, few have examined how inconsistency changes over time. 91 older adults (age 52 to 79) were tested weekly for 36 consecutive weeks on a series of multitrial memory speed (i.e., letter recognition) tasks. A number of multivariate techniques were used to examine how individuals' level of inconsistency changed across weeks and how this change was related to interindividual differences in age and intelligence. Results indicated that (a) inconsistency of performance is a construct separate from the underlying performance ability (i.e., memory speed); (b) inconsistency reduces exponentially with practice; (c) individuals with higher scores on tests of fluid general intelligence (G-sub(f)) reached lower asymptotic levels of inconsistency compared to lower scorers; and (d) after controlling for the systematic effects of practice, variability in inconsistency from week-to-week was more pronounced for individuals with lower G-sub(f) scores compared to individuals with higher scores.

Aged↗
PubMed2005

Neglect of dropout underestimates effects of death in longitudinal studies.

Investigations of terminal declines in mental abilities have assessed cognitive performance at a single time point and retrospectively compared survivors and decedents at a single later census date. Neglect of outcomes other than death, such as dropout, causes a loss of information on the relative frailty of survivors and deceased persons before the census date and on incidence of mortality and frailty among survivors after the census date. This discards information on differences in health status between younger and older survivors. The Heim AH4-1 intelligence test was given to 4,228 people between the ages of 42 and 92 years, and both deaths and dropouts were logged during three successive census periods during the subsequent 11 years. Within and across census periods, effects of impending death and dropout did not differ, decreasing with time from initial assessment. Thus the effects of terminal decline, or indeed of any other variable affecting cognitive performance, are miscalculated if dropout is ignored.

Adult↗
PubMed2004

Practice and drop-out effects during a 17-year longitudinal study of cognitive aging.

Interpretations of longitudinal studies of cognitive aging are misleading unless effects of practice and selective drop-out are considered. A random effects model taking practice and drop-out into account analyzed data from four successive presentations of each of two intelligence tests, two vocabulary tests, and two verbal memory tests during a 17-year longitudinal study of 5,899 community residents whose ages ranged from 49 to 92 years. On intelligence tests, substantial practice effects counteracted true declines observed over 3 to 5 years of aging and remained significant even with intervals of 7 years between successive assessments. Adjustment for practice and drop-out revealed accelerating declines in fluid intelligence and cumulative learning, linear declines in verbal free recall, and no substantial change in vocabulary. Socioeconomic status and basal levels of general fluid ability did not affect rates of decline. After further adjustment for demographics, variability between individuals was seen to increase as the sample aged.

Aged↗
PubMed2003

Older drivers and road safety: the acceptability of a range of intervention measures.

A survey questionnaire was used to ascertain the views of 1932 UK drivers aged between 50 and 90 on a range of measures designed to promote safer driving among the elderly. Factor analysis of the items produced six factors, relating to statistically distinct types of measure. Differences in acceptability on the basis of age and sex were explored. Ratings of the effectiveness of each measure revealed little consensus about which measures would be most effective. Compulsory re-testing after a driving ban, a police power to require an assessment of the driving of anyone observed driving in a risky manner, and a requirement for opticians to report to the licensing authority any driver with sight problems likely to affect driving emerged as the individual measures offering the best combination of acceptability and perceived effectiveness.

Accidents, Traffic↗
PubMed2003

Do clever brains age more slowly? Further exploration of a nun result.

Recent epidemiological evidence suggests that individuals who have higher levels of mental ability in youth experience a slower cognitive decline as they grow old. In a sample of 3,263 Newcastle residents, average scores on a vocabulary test (Raven's 1965 'Mill Hill A') did not vary, while average scores on a test of fluid mental ability (the Heim, 1970, AH 4 (1) group intelligence test) sharply declined with age from 49 to 92 years. In young adults, Mill Hill A scores are good proxies for AH 4 (1) scores. This relationship allowed individuals' youthful AH 4 (1) test scores to be estimated from their current, unchanged, Mill Hill A scores so that age-related changes in AH 4 test scores over the adult life-span could be estimated and compared between high and low ability groups, men and women, and individuals of different levels of socio-economic advantage. The cross-sectional estimated rate of age-related decline in general mental ability was found to be the same for people of all levels of ability and socio-economic advantage, and not to differ between men and women.

Age Factors↗
PubMed2002

Effects of death within 11 years on cognitive performance in old age.

Six different cognitive tests and the Heck Depression Inventory (BDI) were given to 3,572 active community residents aged 49 to 93 years. Causes of death were ascertained for 443 who died between 36 and 3,903 days later. Subsequent survival predicted test scores during the 3,903 days and independently during Days 36 to 1,826 and Days 1,827 to 3,903. Scores on the BDI and cumulative verbal learning and vocabulary tests predicted mortality after demographics and performance on other cognitive tests had been considered. Predictors were similar for deaths from heart disease, malignancies, and other causes. A new finding that cognitive tests did not predict survival duration within the sample of deceased explains previous findings of greater terminal decline in performance for young than for elderly adults.

Aged↗
PubMed2002

Consciousness is slower than you think.

In easy serial choice reaction time tasks (CRT tasks) young adults can very rapidly "correct" nearly all their errors by making the responses that they should have made (error-correcting responses). They are much less accurate at signalling their errors by making the same, deliberate, response to each (error-signalling responses), and they poorly remember errors that they have not signalled or corrected. When instructed to ignore errors they nevertheless involuntarily register them because the response immediately following them (responses following unacknowledged errors) are unusually slow, and they sometimes make involuntary error correction responses. Errors that are neither signalled nor remembered are registered at some level because responses following unacknowledged errors are slowed. Old age does not impair the accuracy of error correction or reduce the proportion of errors that are acknowledged because they are followed by unusually slow responses, but it does reduce the accuracy of error signalling and of recall of errors. Groups of 40 young adults (mean age 20.1 years, SD 1.1) and 40 older adults (mean 71.2 years, SD 5.1) signalled and recalled their errors increasingly accurately as intervals between each response and the next signal were increased from 150 ms to 1000 ms. Error signalling and recall improved as response-signal interval (RSI) durations increased, reaching asymptote at RSIs of 800 ms for the young and 1000 ms for the older adults. Thus processes necessary for conscious and deliberate choice or error-signalling responses and for subsequent recall of errors require more than 150 ms to complete, are slowed by old age, and may be interrupted by onset of new signals occurring earlier than 800 to 1000 ms after completion of an incorrect response.

Adolescent↗