Genetic Mediation of the Associations Among Motor and Perceptual Speed and Adult Cognitive Abilities

Quantitative genetic analyses were conducted to determine the genetic mediation of the associations among motor speed, perceptual speed, and cognitive abilities in normal aging. Measures of motor performance, perceptual speed, and cognitive functioning in four domains (crystallized, fluid, spatial, and memory) were available from the Swedish Adoption/Twin Study of Aging. The sample included 206 twin pairs ranging in age from 44 to 82 years. A Motor Speed factor was constructed from 17 timed measures of motor performance. Heritability of Motor Speed was .26 in middle-aged twins and .00 in older twins. Results indicated that genetic variance in cognitive functioning in the middle-aged cohort may be defined by working memory, whereas genetic variance in the older cohort was defined by perceptual speed. Indications of a nonshared environmental component in the association among motor speed, perceptual speed, and spatial abilities suggest possible frontal lobe involvement.     

Contribution of age, genes, and environment to the relationship between perceptual speed and cognitive ability

The aim of this study was to examine genetic influences on cognitive ability in adulthood in the context of the relationship between perceptual speed and cognitive aging. Quantitative genetic analysis of data from the Swedish Adoption/Twin Study of Aging allowed for estimation of the contribution of age, genetic, and environmental effects to the variance in a latent cognitive factor and to the covariance between the cognitive factor and perceptual speed. The sample included 292 pairs of monozygotic and dizygotic twins. both reared together and reared apart, ranging in age from 40 to 84 years. Analysis of components of total variance in the cognitive factor indicated that 90% of the age-related variance in the cognitive factor was shared with perceptual speed and 70% of the genetic variance in the cognitive factor was shared with perceptual speed. The correlation between the speed and cognitive factors was primarily genetically mediated.     

Intra-individual reaction time variability in schizophrenia, depression and borderline personality disorder

Intra-individual reaction time variability (IIV) in neuropsychological task performance reflects short term fluctuations in performance. Increased IIV has been reported in patients with schizophrenia and could be related to a deficient neural timing mechanism, but the role of IIV in adult patients with other psychiatric disorders has not been established. Therefore, we compared IIV measures obtained in a Go/Nogo task from patients with schizophrenia, major depression and borderline personality disorder. IIV was increased for patients with schizophrenia. When correcting for differences in mean reaction time, depressive and borderline patients also showed increased IIV. Importantly, all groups showed a strong association between IIV and accuracy of task performance. This suggests that increased IIV might be a sensitive marker for the efficiency of top-down attentional control in all diagnostic groups. Aside from these similarities, the complete results including measures of IIV, mean reaction time and accuracy show differential patterns for patients with schizophrenia compared to those with borderline personality disorder or depression. These results are discussed with respect to common versus disorder-specific neural mechanisms underlying increased IIV.     

工作记忆容量和加工速度在归纳推理能力老化中的作用

利用结构方程模型考察了工作记忆容量和加工速度在归纳推理老化中的作用。样本为217名社区老人。结果发现：(1)工作记忆容量在归纳推理老化中具有重要作用．语音环路和视空问初步加工系统在推理过程巾参与程度相当。(2)在年龄和归纳推理能力之问存在年龄——加工速度——工作记忆容量——归纳推理这样一条层级关系。年龄、加工速度和工作记忆容量共同解释归纳推理中57％的变异。     

Speed of information processing and general intelligence

This study investigates the relationship between a number of measures of speed of cognitive information-processing and intelligence test scores. One hundred university students were given five tests of speed-of-processing, measuring their speed of encoding, short-term memory scanning, long-term memory retrieval, efficiency of short-term memory storage and processing, and simple and choice reaction time or decision-making speed. They were also given the Wechsler Adult Intelligence Scale and the Raven Advanced Progression Matrices. A number of multiple regression analyses show that the cognitive processing measures are significantly related to IQ scores. Other analyses indicate that this relationship cannot be attributed to the common content shared by the reaction time and the intelligence tests, nor to the fact that parts of the WAIS are timed. It is concluded that the reaction time tests measure basic cognitive operations which are involved in many forms of intellectual behavior, and that individual differences in intelligence can be attributed, to a moderate extent, to variance in the speed or efficiency with which individuals can execute these operations.     

Intraindividual reaction time variability predicts prospective memory failures in older adults

This study investigated the relationship between intraindividual variability (IIV) in reaction time and prospective memory errors in older adults using data from the Zurich Longitudinal Study of Cognitive Aging (n = 336 individuals aged 66–81 years). The results indicated that increased IIV measured from independent tasks was associated with a greater proportion of prospective memory errors. These significant findings were not influenced by age and did not vary according to prospective memory cue type. Variability is thought to reflect fluctuations in attentional and executive control and these attentional processes may also impact on prospective memory through failure to detect the target cue. The findings suggest, therefore, that measures of variability may have some potential in the identification of older persons who are more vulnerable to everyday errors such as prospective memory failures.     

Age differences in fluid intelligence: contributions of general slowing and frontal decline

The current study examined the contributions of general slowing and frontal decline to age differences in fluid intelligence. Participants aged 20-89 years completed Block Design, Matrix Reasoning, simple reaction time, choice reaction time, Wisconsin Card Sorting, and Tower of London tasks. Age-related declines in fluid intelligence, speed of processing, and frontal function were observed. Hierarchical regression analyses showed that the processing speed and frontal function measures accounted for significant variance in fluid intelligence performance, but there was also a residual effect of age after controlling for each variable individually as well as both variables. An additional analysis showed that the variance in fluid intelligence that was attributable to processing speed was not fully shared with the variance attributable to frontal function. These findings suggest that the age-related decline in fluid intelligence is due to general slowing and frontal decline, as well as other unidentified factors.     

Relation between speed of reaction and psychometric tests of mental ability in musculoskeletal injury-prone subjects

Long reaction time (RT), long choice reaction time (CRT), and low scores on psychometric tests of mental ability (MA) have in previous studies been related to musculoskeletal injuries. There has been controversy concerning the relation between slow reaction and low-grade MA recently, the old hypothesis of negative correlation between RT and MA being discussed. The aim of this study was to analyze the relation between speed of reaction and MA. For a sample of 123 volunteer healthy young men simple RT, choice RT, and spatial (block design), verbal and arithmetic components of MA were tested. A principal component analysis was performed and the factor matrix was rotated orthogonally using the varimax method. Two factors were extracted accounting for 73% of the total variance in data space. The mental ability factor, which was responsible for 70% of the variance in factor space, was comprised of components of MA and choice RT. The speed of reaction factor accounted for the remaining 30% of the variance in factor space and was comprised of simple and choice RTs. As choice RT had significant loading on the mental ability factor, the subjects having scores in the lowest quartile on both choice RT and MA total score were compared with the independent expected value by using the chi-squared test. The results of low-grade MA and slow choice reaction were not independent. Accordingly, the results do not support the entire distinction between traditional mental ability or convergent thinking and speed of reaction in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age changes in processing speed as a leading indicator of cognitive aging

Bivariate dual change score models were applied to longitudinal data from the Swedish Adoption/Twin Study of Aging to compare the dynamic predictions of 2-component theories of intelligence and the processing speed theory of cognitive aging. Data from up to 5 measurement occasions covering a 16-year period were available from 806 participants ranging in age from 50 to 88 years at the first measurement wave. Factors were generated to tap 4 general cognitive domains: verbal ability, spatial ability, memory, and processing speed. Model fitting indicated no dynamic relationship between verbal and spatial factors, providing no support for the hypothesis that age changes in fluid abilities drive age changes in crystallized abilities. The results suggest that, as predicted by the processing speed theory of cognitive aging, processing speed is a leading indicator of age changes in memory and spatial ability, but not verbal ability.     

Speed of word recognition and vocabulary knowledge in infancy predict cognitive and language outcomes in later childhood

The nature of predictive relations between early language and later cognitive function is a fundamental question in research on human cognition. In a longitudinal study assessing speed of language processing in infancy, Fernald, Perfors and Marchman (2006) found that reaction time at 25 months was strongly related to lexical and grammatical development over the second year. In this follow-up study, children originally tested as infants were assessed at 8 years on standardized tests of language, cognition, and working memory. Speed of spoken word recognition and vocabulary size at 25 months each accounted for unique variance in linguistic and cognitive skills at 8 years, effects that were attributable to strong relations between both infancy measures and working memory. These findings suggest that processing speed and early language skills are fundamental to intellectual functioning, and that language development is guided by learning and representational principles shared across cognitive and linguistic domains.     

The sensory‐cognition association in adulthood: Different magnitudes for processing speed,inhibition, episodic memory,and false memory?

One hundred and forty-six participants (age range = 20-80) completed a battery of tests designed to measure visual acuity, processing speed, inhibition, episodic memory and false memory. The relations between visual acuity and general cognitive ability, as well as between visual acuity and the indicators of this construct, were evaluated with structural equation modeling. The measurement model confirmed that the indicators of the individual cognitive abilities could be grouped into a general cognitive functioning factor. However, the relation between episodic and false memory was not completely explained by the shared association with this general factor. Furthermore, visual acuity predicted approximately half of the age-related variance in the general cognition factor. Also, the proportion of age-related variance shared with vision was highest in inhibition and lowest in false memory. The results are discussed in the light of common cause accounts of cognitive aging.     

Writing and reading skills as assessed by teachers in 7-year olds: A behavioral genetic approach

A behavioral genetic analysis of general writing ability was conducted using teacher assessments based on UK National Curriculum criteria for a sample of 3296 same-sex pairs of 7-year-old twins. Writing was highly heritable within the normal range (0.66) and at the low extreme (0.70). Environmental influences were almost all non-shared, with shared environmental estimates negligible (0.07 normal range, 0.06 low extreme). Bivariate genetic analyses of teacher assessments of writing and reading indicated that 69% of the genetic influences on writing were in common with those on reading, and that the two skills shared all of their shared environmental influences. In contrast, non-shared environmental factors are largely specific, with 86% independent of those on reading.     

Verbal and spatial short-term memory: common sources of developmental change?

Verbal and spatial span, articulation and tapping rate, and verbal and spatial speed-of-search tasks were administered to sixty 6- to 12-year-olds. A variance-partitioning procedure was then used to identify age-related and age-invariant components of variance in span. Outcomes were very similar for verbal and spatial span, in particular, (i) most of the age-related variance was shared by the speed-of-search and rate predictors, (ii) articulation rate provided an age-independent contribution, (iii) changing-state versions of predictor tasks did not account for variance over steady-state versions, and (iv) predictors of the same modality as the span task did not outperform predictors of the other modality. We conclude that verbal and spatial short-term memory appear to rely on similar processes when serial recall is required and that developments in span are closely tied to increases in processing speed.     

Twins and the study of rater (dis)agreement

Genetically informative data can be used to address fundamental questions concerning the measurement of behavior in children. The authors illustrate this with longitudinal multiple-rater data on internalizing problems in twins. Valid information on the behavior of a child is obtained for behavior that multiple raters agree upon and for rater-specific perception of the child's behavior. Rater-disagreement variance varsigma2(rd) accounted for 35% of the individual differences in internalizing behavior. Up to 17% of this varsigma2(rd) was accounted for by rater-specific additive genetic variance varsigma2(Au). Thus, the disagreement should not be considered only to be bias/error but also as representing the unique feature of the relationships between that parent and the child. The longitudinal extension of this model helps to make a distinction between measurement error and the raters' unique perception of the child's behavior. For internalizing behavior, the results show large stability across time, which is accounted for by common additive genetic and common shared environmental factors. Rater-specific shared environmental factors show substantial influence on stability. This could mean that rater bias may be persistent and affect longitudinal studies.     

Mapping the developmental constraints on working memory span performance

This study investigated the constraints underlying developmental improvements in complex working memory span performance among 120 children of between 6 and 10 years of age. Independent measures of processing efficiency, storage capacity, rehearsal speed, and basic speed of processing were assessed to determine their contribution to age-related variance in complex span. Results showed that developmental improvements in complex span were driven by 2 age-related but separable factors: 1 associated with general speed of processing and 1 associated with storage ability. In addition, there was an age-related contribution shared between working memory, processing speed, and storage ability that was important for higher level cognition. These results pose a challenge for models of complex span performance that emphasize the importance of processing speed alone.     

Cognitive abilities profiles of Caucasian vs Japanese subjects in the Hawaii Family Study of Cognition

General intelligence (the unrotated first principal component) was partialled out of the cognitive abilities factors—verbal ability, spatial ability, perceptual speed, and visual memory—obtained for the 15 tests of cognitive abilities used in the Hawaii Family Study of Cognition (HFSC). The resulting cognitive abilities profiles indicated that HFSC subjects of Caucasian ancestry scored higher relative to subjects of Japanese ancestry on the verbal and visual memory factors, but lower on the spatial and perceptual speed factors. This ethnic group difference in the shape of the cognitive abilities profiles was found to be highly consistent across sexes and generations, in spite of the large mean differences across these groups in factor scores.     

Genetic architecture of context processing in late middle age: more than one underlying mechanism

Studies comparing young and older adults suggest a deficit in processing context information as a key mechanism underlying cognitive aging. However, the genetic architecture of context processing has not been examined. Consistent with previous results, we found evidence of functionally dissociable components of context processing accuracy in 1127 late middle-aged twins ages 51-60. One component emphasizes use of context cues to prepare responses (proactive cognitive control), and the other emphasizes adjustment of responses after probes are presented (reactive control). Approximately one-quarter of the variance in each component was accounted for by genes. Multivariate twin analysis indicated that genetic factors underlying two important components of context processing were independent of one another, thus implicating more than one underlying mechanism. Slower reaction time (RT) on noncontext processing trials was positively correlated with errors on the strongly proactive control component on which young adults outperform older adults, but RT was negatively correlated with errors on the strongly reactive control component on which older adults perform better. Although this RT measure was uncorrelated with chronological age in our age-homogeneous sample, slower RT was associated with performance patterns that were more like older adults. However, this did not generalize to other processing speed measures. Genetic correlations, which reflect shared genetic variance, paralleled the phenotypic correlations. There was also a positive genetic correlation between general cognitive ability and accuracy on the proactive control component, but there were still mostly distinct genetic influences underlying these measures. In contrast, the reactive control component was unrelated to general cognitive ability.     

Cross-sequential analysis of genetic influences on cognitive ability in the swedish adoption/twin study of aging

Abstract

Cross-sequential methods of analysis were applied to cognitive data from the Swedish Adoption/Twin Study of Aging. Thirteen measures of cognitive ability assessing four major domains (verbal, spatial, memory, and perceptual speed) were collected at two times of measurement separated by a three-year interval. Data were available from 41 pairs of monozygotic twins reared apart (MZA), 54 pairs of monozygotic twins reared together (MZT), 86 pairs of dizygotic twins reared apart (DZA), and 73 pairs of dizygotic twins reared together (DZT) ranging in age from 41 to 84 years. Cross-sectional differences and longitudinal changes in total variance and sources of variance were examined. With a few exceptions, both cross-sectional and longitudinal stability were found for total variance. In addition, few cross-sectional differences and longitudinal changes were found for genetic and environmental components of variance.     

Infant visual recognition memory: independent contributions of speed and attention

Relations between infant visual recognition memory and later cognition have fueled interest in identifying the underlying cognitive components of this important infant ability. The present large-scale study examined three promising factors in this regard--processing speed, short-term memory capacity, and attention. Two of these factors, attention and processing speed (but, surprisingly, not short-term memory capacity), were related to visual recognition memory: Infants who showed better attention (shorter looks and more shifts) and faster processing had better recognition memory. The contributions of attention and processing speed were independent of one another and were similar at all ages studied--5, 7, and 12 months. Taken together, attention and speed accounted for 6%-9% of the variance in visual recognition memory, leaving a considerable, but not unexpected, portion of the variance unexplained.