Aerobic fitness and response variability in preadolescent children performing a cognitive control task.

Objective: To investigate the relationship between aerobic fitness and cognitive variability in preadolescent children. Method: Forty-eight preadolescent children (25 males, 23 females, mean age = 10.1 years) were grouped into higher- and lower-fit groups according to their performance on a test of aerobic capacity (VO2max). Cognitive function was measured via behavioral responses to a modified flanker task. The distribution in reaction time was calculated within each participant to assess intraindividual variability of performance. Specifically, the standard deviation and coefficient variation of reaction time were used to represent cognitive variability. Results: Preadolescent children, regardless of fitness, exhibited longer reaction time, increased response variability, and decreased response accuracy to incongruent compared to congruent trials. Further, higher-fit children were less variable in their response time and more accurate in their responses across conditions of the flanker task, while no group differences were observed for response speed. Conclusion: These findings suggest that fitness is associated with better cognitive performance during a task that varies cognitive control demands, and extends this area of research to suggest that intraindividual variability may be a useful measure to examine the relationship between fitness and cognition during preadolescence. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effect of dimensional salience and salience of variability on problem solving: A developmental study.

Presented a matching task to 120 6-20 yr olds to investigate the relative influence of dimensional salience and salience of variability on problem solving. The task included 4 dimensions: form, color, number, and position. On each problem, 1 dimension was relevant and the other 3, which could be either constant or variable, were irrelevant for solution. Ss were asked to find which of 2 stimuli was more similar to a standard stimulus. Results show the same dimensional hierarchy for both reaction time and error scores. The effect of variability, as measured by reaction time and error scores, increased with increasing number of variable irrelevant dimensions and decreased with age. The effect of variability proved to be greater than the effect of dimensions. The implications of the relative influence of dimensional salience and salience variability for problem solving are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depression, anxiety, and within-person variability in adults aged 18 to 85 years.

Mild depression and anxiety were investigated in relation to measures of within-person (WP) variability and mean reaction time from psychomotor, executive function, visual search, and word recognition tasks in a continuous age range (18?85 years, M = 50.33, SD = 20.37) of 300 community-dwelling adults. Structural equation modeling identified a significant Age × Depression interaction in relation to visual search for measures of WP variability but not for mean reaction time. Older more depressed adults exhibited greater variability. WP variability in executive function and other cognitive constructs covaried, and the significant Age × Depression interaction with visual search was accounted for by WP variability in executive control. The findings suggest that age- and depression-related reductions in attentional resources may contribute to increased variability in visual search and that variability in executive control may be the mechanism underlying these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Age and sex differences in reaction time in adulthood: Results from the United Kingdom Health and Lifestyle Survey": Correction.

Reports an error in "Age and sex differences in reaction time in adulthood: Results from the United Kingdom Health and Lifestyle Survey" by Geoff Der and Ian J. Deary (Psychology and Aging, 2006[Mar], Vol 21[1], 62-73). In the article, the link to supplemental material is incorrect. The correct supplemental link follows. Supplemental materials are available online at http://dx.doi.org/10.1037/0882-7974.21.1.62.supp. (The following abstract of the original article appeared in record 2006-03906-007.) Reaction times (RTs) slow and become more variable with age. Research samples are typically small, biased, and of restricted age range. Consequently, little is known about the precise pattern of change, whereas evidence for sex differences is equivocal. The authors reanalyzed data for 7,130 adult participants in the United Kingdom Health and Lifestyle Survey, originally reported by F. A. Huppert (1987). The authors modeled the age differences in simple and 4-choice reaction time means and variabilities and tested for sex differences. Simple RT shows little slowing until around 50, whereas choice RT slows throughout the adult age range. The aging of choice RT variability is a function of its mean and the error rate. There are significant sex differences, most notably for choice RT variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of age on consistent and varied semantic-category search performance.

Three experiments examined age-related consistent mapping (CM) and varied mapping (VM) practice effects. In separate experiments, young (age, 19–22), middle-aged (37–50), and older (64–88) adults' performance was examined using semantic-category and letter-based search paradigms. After extensive practice, major age differences occurred in CM search. Young and middle-aged subjects showed near-zero comparison slopes, large reductions in mean reaction times, and substantial reductions in response variability. Although older adults' reaction time decreased with CM practice, the reduction in reaction time, comparison slope, and response variability was small compared with the other groups. In VM search, older subjects were slower than the other age groups, but all groups exhibited similar linear set-size functions, search termination, and comparison-load effects. We concluded that age-associated declines in cognitive performance may be due in large part to the degree with which older adults can acquire or use automatic processes to perform tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age and sex differences in reaction time in adulthood: Results from the United Kingdom Health and Lifestyle Survey.

[Correction Notice: An erratum for this article was reported in Vol 24(1) of Psychology and Aging (see record 2009-03151-017). In the article, “Age and Sex Differences in Reaction Time in Adulthood: Results From the United Kingdom Health and Lifestyle Survey” by Geoff Der and Ian J. Deary (Psychology and Aging, Vol. 21, No. 1, pp. 62–73), the link to supplemental material is incorrect. The correct supplemental link follows. Supplemental materials are available online at http://dx.doi.org/10.1037/0882-7974.21.1.62.supp.] Reaction times (RTs) slow and become more variable with age. Research samples are typically small, biased, and of restricted age range. Consequently, little is known about the precise pattern of change, whereas evidence for sex differences is equivocal. The authors reanalyzed data for 7,130 adult participants in the United Kingdom Health and Lifestyle Survey, originally reported by F. A. Huppert (1987). The authors modeled the age differences in simple and 4-choice reaction time means and variabilities and tested for sex differences. Simple RT shows little slowing until around 50, whereas choice RT slows throughout the adult age range. The aging of choice RT variability is a function of its mean and the error rate. There are significant sex differences, most notably for choice RT variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of stability of performance in patients with traumatic brain injury: Variability and consistency on reaction time tests.

The stability of performance of reaction times (RTs) on 3 visual discrimination tasks was assessed in patients with varying severity of traumatic brain injury (TBI) and in matched control Ss. Results were analyzed for group and individual variability and consistency of performance over time. There was significantly greater intersubject (group) variability in the TBI group. Individual patients (intrasubject) tended to be more variable in performance and less consistent over time than control Ss, but this occurred only with specific measures, which suggests that increased lack of stability in performance is not a general impairment after brain damage but requires specific analyses for identification of performance differences. This intrasubject variability was indepedent of test–retest and split-half test reliability. No obvious factors such as severity of brain injury were related to the variability and inconsistency of performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confined placental chimerism: prenatal and postnatal cytogenetic and molecular analysis, and pregnancy outcome

The aim of the present study was to compare the mental capacity changes in school teachers, depending on age and type of school. 120 teachers drawn from the secondary and technical schools of Sofia were divided into two groups of younger (mean 31.5 yrs) and older (mean 47.5 yrs) age. They were given two monotonous visual tasks, which differed in complexity: of discrimination and of categorization. The behavioral measures of performance revealed lower efficiency in categorization due mostly to the so-called "premature" or "impulsive" reactions. Significant positive correlations were found between age and within-individual variability of reaction time, suggesting an earlier onset of the aging processes in the investigated population. The decrease in performance efficiency which was age-related was most expressed in the secondary school teachers. It was concluded that the changes of mental capacity can be regarded as an indirect indicator of the occupational stress of the school teachers.     

The influence of aging and target motion on the control of prehension

The purpose of this study was to examine age-related differences in reaching behavior when younger (mean age = 26.0 years) and older (mean age = 70.1 years) individuals were required to reach toward and grasp both small and large targets that were either stationary or moving. The older subjects had shorter movement times, and smaller within-subject movement time variability than younger subjects. Also, the deceleration of the reach was shorter for older subjects, indicating that they were not making extensive use of on-line feedback, and were instead utilizing anticipatory control strategies. There were no age differences in the size of the maximum grasp around the target, but the timing of the grasp was influenced by target motion for the younger subjects, suggesting on-line control for the younger subjects only.     

Age, variability, and speed: Between-subjects diversity.

Two independent data sets were selected to examine the interrelations among reaction time (RT), between-subject variability or diversity (SD), and age. In both data sets, a strong correlation between RT and SD was obtained. This strong correlation was not affected when age was controlled in a partial correlation analysis. On the other hand, a weaker but significant correlation was obtained between age and SD. This correlation was eliminated when RT was controlled in a partial correlation analysis. Our analyses of the two data sets also indicated that the relation between RT and SD is identical for both young and elderly groups. Thus, the greater diversity often observed in performances of older groups is a direct consequence of slowing, rather than an independent effect of advancing age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beat-to-beat QRS variability in the 12-lead ECG and the detection of coronary artery disease

The aim of this article was to study beat-to-beat QRS variability in patients with ischemia and old myocardial infarction using the 12-lead resting electrocardiogram (ECG). The variability analysis was based on beats that have been synchronized in time with an iterative alignment technique. The QRS variability was measured in patients submitted for myocardial scintigraphy. Those with a normal myocardial scintigraphy (called NO, n = 34, mean age 57 years, 23 women) were compared with a group with both myocardial infarction and exercise-induced ischemia (called ISCINF, n = 27, mean age 57 years, 5 women). The mean QRS variability was somewhat smaller in lead I in ISCINF than in NO, and there was no statistically significant difference in QRS variability among the groups in leads II, III, and V1-V6. Using a multivariate approach, the joint variability in leads I, II, II, and V1-V6 was used for calculating receiver operating characteristics based on a leave-one-out procedure. The sensitivity for detecting coronary artery disease was 75% at a specificity of 50%. It is concluded that beat-to-beat QRS variability in the 12-lead ECG does not discriminate between the presence and absence of coronary artery disease sufficiently well for clinical purposes.     

Practice effects in reaction-time tasks in brain-injured patients.

"A study of performance trends in simple and choice reaction time tasks in nonpsychotic, brain-injured patients and a matched group of control patients indicated that, within the limits investigated (30 trials in each task), there were no significant practice effects with respect to mean reaction time for either group in either task. The performances of those brain-injured patients whose initial reaction times were within normal limits also failed to reflect significant practice effects… . The brain-injured patients showed a significant increase in intra-individual variability in simple reaction time with continued practice. However, this difference in trends was not found in the choice reaction task." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The variability of human, BOLD hemodynamic responses

Cerebral hemodynamic responses to brief periods of neural activity are delayed and dispersed in time. The specific shape of these responses is of some importance to the design and analysis of blood oxygenation level-dependent (BOLD), functional magnetic resonance imaging (fMRI) experiments. Using fMRI scanning, we examine here the characteristics and variability of hemodynamic responses from the central sulcus in human subjects during an event-related, simple reaction time task. Specifically, we determine the contribution of subject, day, and scanning session (within a day) to variability in the shape of evoked hemodynamic response. We find that while there is significant and substantial variability in the shape of responses collected across subjects, responses collected during multiple scans within a single subject are less variable. The results are discussed in terms of the impact of response variability upon sensitivity and specificity of analyses of event-related fMRI designs.     

Does variability increase with age? An archival study of cognitive measures.

It is often asserted that older people are more variable than younger people; however, the published data do not always support this statement. To examine directly the applicability of the assertion, measures of reaction time (RT), memory, and intelligence from studies published in Psychology and Aging and the Journal of Gerontology from 1986 to 1990 were examined. The coefficients of variability calculated from data published in studies in which a group of younger people was compared with a group of older people indicated that variability was greater among older participants on measures of RT, memory, and fluid intelligence but not crystallized intelligence. Further examination of data bearing on relative variability is indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Management of stage III breast cancer

The influence of several methodological factors on mean values of sister chromatid exchanges (SCEs) and micronuclei (MN) in peripheral lymphocytes of 1,650 subjects was analyzed. Donors belonged to a general healthy population living in Pisa and in two nearby small cities: Cascina and Navacchio (Ca-Na). Blood samples were collected over a period of 29 months and processed in three different laboratories of the some institute. Slides were analyzed by several scorers. Our data showed that lymphocyte proliferation indexes (PIs) and baseline mean values of SCEs were affected mainly by sampling period. This factor accounted for a percentage ranging from roughly 10% (Pisa) to 20% (Ca-Na) of total SCE variance and from roughly 10% (Pisa) to 13% (Ca-Na) of total PIs variance. A marginal effect was attributable to the different laboratories involved (maximum 3% for SCEs and 7% for PIs). The sampling period variable included many sources of variability such as culture media batches, fetal calf serum, PHA, BrdUrd, and seasonality. MN counts revealed a more marked dependence on processing laboratories. This factor accounted for a percentage of roughly 10% (Pisa and Ca-Na) of total variance, while the sampling period was marginally effective (about 1-4% of total variability). Because laboratories were equipped and supplied with the same materials and consumables and technicians were rotated constantly, the only variable ascertained was represented by the three different models of CO2 incubators used for lymphocyte culturing. When "month" and "incubator" variables were considered jointly, experimental variability accounted for 15-20% of total variance, both for PIs and mean values SCEs and MN. The variability due to slide scoring was reduced by assigning each slide to five different scorers and matching low with high scorers in each group. Present data show that when the study is performed under these controlled conditions, about 20% of total interdonor variability can be explained by experimental or seasonal factors.     

Examining the Time Course of Indexical Specificity Effects in Spoken Word Recognition.

Variability in talker identity and speaking rate, commonly referred to as indexical variation, has demonstrable effects on the speed and accuracy of spoken word recognition. The present study examines the time course of indexical specificity effects to evaluate the hypothesis that such effects occur relatively late in the perceptual processing of spoken words. In 3 long-term repetition priming experiments, the authors examined reaction times to targets that were primed by stimuli that matched or mismatched on the indexical variable of interest (either talker identity or speaking rate). Each experiment was designed to manipulate the speed with which participants processed the stimuli. The results demonstrate that indexical variability affects participants' perception of spoken words only when processing is relatively slow and effortful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroticism as Mental Noise: A Relation Between Neuroticism and Reaction Time Standard Deviations.

Those higher in neuroticism are often more variable in their behavior and experience. On the basis of this observation, the authors hypothesized that the trait of neuroticism might be correlated with the variability of performance pertaining to relatively basic cognitive operations. Three studies involving 242 college undergraduates supported this prediction in that neuroticism correlated positively with the variability of performance across trials of reaction time tasks. These results link neuroticism to cognitive noise that intervenes between stimulus and response. Such noise has been associated with executive dysfunctions (e.g., frontal lobe injury) in previous research. The present findings are potentially useful for understanding why neuroticism often correlates with variations in the functionality of cognition and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in big five behavior averages and variabilities across the adult life span: Moving beyond retrospective, global summary accounts of personality.

In 3 intensive cross-sectional studies, age differences in behavior averages and variabilities were examined. Three questions were posed: Does variability differ among age groups? Does the sizable variability in young adulthood persist throughout the life span? Do past conclusions about trait development, based on trait questionnaires, hold up when actual behavior is examined? Three groups participated: young adults (18–23 years), middle-aged adults (35–55 years), and older adults (65–81 years). In 2 experience-sampling studies, participants reported their current behavior multiple times per day for 1- or 2-week spans. In a 3rd study, participants interacted in standardized laboratory activities on 8 occasions. First, results revealed a sizable amount of intraindividual variability in behavior for all adult groups, with average within-person standard deviations ranging from about half a point to well over 1 point on 6-point scales. Second, older adults were most variable in Openness, whereas young adults were most variable in Agreeableness and Emotional Stability. Third, most specific patterns of maturation-related age differences in actual behavior were more greatly pronounced and differently patterned than those revealed by the trait questionnaire method. When participants interacted in standardized situations, personality differences between young adults and middle-aged adults were larger, and older adults exhibited a more positive personality profile than they exhibited in their everyday lives. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural equation models of relationships between exercise and cognitive abilities.

Data were obtained from 300 men and women aged 55 to 91. Separate structural equation models of relationships between physical exercise and 3 cognitive performance variables—reaction time (RT), working memory, and reasoning—fit the data well. Other variables in the models were age, health, education, and morale. Age and exercise affected each performance variable directly; education had a direct effect on reasoning only. There were also indirect effects of age and health on performance variables, mediated through exercise. The main hypothesis of the study, that exercise contributes to performance, was supported. A large decrease in model fit resulted when the path from exercise to each variable was deleted. Hypotheses that age-related deficits are primarily accounted for by lack of exercise or by poor health were not supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive ability at age 11 and 70 years, information processing speed, and APOE variation: The Lothian Birth Cohort 1936 study.

The e4 allele of the apolipoprotein E (APOE) gene confers risk of Alzheimer's disease and, in some studies, relates to cognitive ability and decline in older people without Alzheimer's disease. Its relationship with processing speed, a contributor to cognitive decline with age, is largely unknown. This study tests the association of APOE with cognition and speed, with and without covarying childhood mental ability. The 1,013 participants were tested on cognitive ability at age 11 as part of the Scottish Mental Survey of 1947 and, at age 70, were tested on reasoning, working memory, information processing speed, and executive function. The results showed that APOE was associated with the general cognitive factor, 2 nonverbal tests, and choice reaction time (RT) variability; as expected, the e4 allele was the risk allele. RT measures and a general speed factor were nonlinearly related to APOE when factoring childhood ability (p