Uncoupling learning from initial recall: The relationship between speed and memory deficits in old age

Abstract

Nettelbeck & Rabbitt (1992) found that measures of speed of performance with low knowledge requirements (four-choice reaction time, inspection time and coding-substitution) accounted substantially for age-related changes among 104 persons aged from 54 to 85 years in a number of more complex cognitive measures reflecting general fluid ability. However, the numbers of words recalled from a list after either a single brief viewing of each word, or following a cumulative learning procedure across four trials, provided an exception to this general trend, leading to the conclusion that some aspects of memory may be independent of mental speed. A follow-up of 82 of the same people 18-20 months later was designed to partition performance in a similar cumulative learning procedure into an initial first recall component and a subsequent learning component. This was accomplished by fitting individual cumulative learning data with a hyperbolic power function which met the theoretical requirement of defining separate initial recall and learning parameters. These parameters were found to be independent and it was concluded that learning involved rehearsal, whereas first recall did not. The hyperbolic power function provided a good account for 92 per cent of individual cases. Analyses which combined Nettelbeck & Rabbitt's (1992) data with new measures confirmed the reliability of these authors' results. Furthermore, it was found that first recall, but not learning, was mediated by processing speed. Learning was relatively unaffected by age-related slowing in mental speed, suggesting that Nettelbeck & Rabbitt's results were the consequence of a strong rehearsal component in their memory tasks. Thus, while mental slowing is clearly one important aspect of cognitive decline during old age, it does not constitute a sufficient explanation for changes in all areas of cognitive functioning. Specifically, age-decline in rate of learning with rehearsal appeared to be independent of slowing in speed of information processing.

A study of performance on tests from the CANTAB battery sensitive to frontal lobe dysfunction in a large sample of normal volunteers: Implications for theories of executive functioning and cognitive aging

“…Thus, the relationship of age to performance on these tests was also not wholly secondary to changes in information-processing rate. The persistent relationship between age and the test of visuospatial paired associates learning is consistent with data reported by Nettelbeck and Rabbitt (1992) and by Nettelbeck et al (1996), even though they employed somewhat different indices of speed of information-processing. Our results are also compatible with those reported by Rabbitt and Maylor (1991) and Baddeley (1996), which also suggest that certain executive functions may be related to age, over and above any relationships with speed of processing and IQ.…”

Toward Understanding Age-Related Memory Loss in Late Adulthood

“…It appears that the role of speed of processing in remembering may be particularly important during rehearsal or encoding [18,24], as Salthouse [14] originally theorised.…”

A Growth Curve Model of Learning Acquisition among Cognitively Normal Older Adults

“…For example, Royall and colleagues have recently demonstrated that among residents of a continuing-care retirement community, learning rate over trials on the CVLT predicts dementia type (Alzheimer's-type versus nonAlzheimer's type), but baseline cross-sectional performance did not (Royall, Palmer, Chiodo, & Polk, 2003). The authors suggest that performance on the CVLT learning trials Rabbitt, Wilson, & Batt (1996) who found using a serial learning task that initial recall and learning were statistically uncorrelated, and that initial recall was more strongly related to indices of processing speed.…”

“…For example, Royall and colleagues have recently demonstrated that among residents of a continuing-care retirement community, learning rate over trials on the CVLT predicts dementia type (Alzheimer's-type versus nonAlzheimer's type), but baseline cross-sectional performance did not (Royall, Palmer, Chiodo, & Polk, 2003). The authors suggest that performance on the CVLT learning trials Rabbitt, Wilson, & Batt (1996) who found using a serial learning task that initial recall and learning were statistically uncorrelated, and that initial recall was more strongly related to indices of processing speed.Previous research has also highlighted other predictors of initial recall and learning (e.g., sociodemographic characteristics such as age, gender, race, and education, and health factors). With respect to age, a number of cross-sectional and longitudinal studies have found evidence of negative age differences and age-related decline performance on measures of episodic memory (see Bäckman, Small, Wahlin, & Larson, 2000).…”

“…The authors suggest that performance on the CVLT learning trials captures the quality of hippocampal functioning. Another example is represented by the work of Nettelbeck, Rabbitt, Wilson, & Batt (1996) who found using a serial learning task that initial recall and learning were statistically uncorrelated, and that initial recall was more strongly related to indices of processing speed.…”