Intelligence and reaction times in the Hick, Sternberg and Posner paradigms

The relationship between psychometric intelligence and reaction times (RTs) in three well-known elementary cognitive tasks (Hick simple and choice reaction time task, Sternberg's short-term memory scanning, Posner's letter matching) was studied in a sample of 116 participants. In conformity with other studies mean RTs and intraindividual variabilities (SDs) of RT were correlated significantly with Raven's Advanced Progressive Matrices (APM). On the basis of the mental speed theory the processing measures or component scores (like slopes in the Hick and Sternberg paradigm and the NI-PI measure in the Posner task) should give the most substantial relationships with intelligence. However, as in other previous studies these measures displayed rather low, albeit significant, relationships with intelligence, which was probably due to the low reliability of these parameters. For the Posner paradigm, we proposed alternative approaches to compute an indicator for long-term memory (LTM) access that gave substantial correlations with intelligence. We conclude that LTM access is significantly associated with psychometric intelligence, whereas up to now there has been no unequivocal evidence for a substantial relationship between short-term memory access in the Sternberg task and intelligence.     

Change in intraindividual variability over time as a key metric for defining performance-based cognitive fatigability

Cognitive fatigability is conventionally quantified as the increase over time in either mean reaction time (RT) or error rate from two or more time periods during sustained performance of a prolonged cognitive task. There is evidence indicating that these mean performance measures may not sufficiently reflect the response characteristics of cognitive fatigue. We hypothesized that changes in intraindividual variability over time would be a more sensitive and ecologically meaningful metric for investigations of fatigability of cognitive performance. To test the hypothesis fifteen young adults were recruited. Trait fatigue perceptions in various domains were assessed with the Multidimensional Fatigue Index (MFI). Behavioral data were then recorded during performance of a three-hour continuous cued Stroop task. Results showed that intraindividual variability, as quantified by the coefficient of variation of RT, increased linearly over the course of three hours and demonstrated a significantly greater effect size than mean RT or accuracy. Change in intraindividual RT variability over time was significantly correlated with relevant subscores of the MFI including reduced activity, reduced motivation and mental fatigue. While change in mean RT over time was also correlated with reduced motivation and mental fatigue, these correlations were significantly smaller than those associated with intraindividual RT variability. RT distribution analysis using an ex-Gaussian model further revealed that change in intraindividual variability over time reflects an increase in the exponential component of variance and may reflect attentional lapses or other breakdowns in cognitive control. These results suggest that intraindividual variability and its change over time provide important metrics for measuring cognitive fatigability and may prove useful for inferring the underlying neuronal mechanisms of both perceptions of fatigue and objective changes in performance.     

Relations between mental performance and reaction time: New aspects of an old problem

The relation between simple and complex reaction time and psychometrically determined mental performance was reexamined with 486 subjects of above-average intelligence. Various standardized tests measuring aspects of cognitive ability, memory and ability to concentrate were used. Simple and complex reaction times were measured using the Klebelsberg modification of the Mierke apparatus. Correlations between complex reaction time and mental performance as observed by other investigators were mostly confirmed. We found, however, the strongest and most consistent correlations with tests measuring short-term memory; ability to concentrate and spatial ability. On the other hand, tests known and shown again in this paper to load highly on Spearman's general factor g, such as verbal abilities; combinatoric thinking; abstraction; or calculation gave only trivial, and, in most cases, nonsignificant correlations with complex reaction time. We even observed a negative (though, for our data, not significant) correlation between g-loadings of subtests and their correlations with complex reaction time for the only complete standardized intelligence test used in this study, the “Intelligenz-Strukturtest (Amthauer).” Therefore, this study does not support the hypothesis that fast processing of complex information as measured by complex reaction time is the decisive component of the general factor of intelligence g.     

Individual differences in performance on elementary cognitive tasks (ECTs): lawful vs. problematic parameters.

Over the past 2 decades, the cognitive-correlates approach has dominated investigations into the nature of intelligence. This research program relies on a number of processing speed parameters (apart from "average performance"). These measures include the slope, intercept, and intraindividual variability of both decision time and movement time. By correlating these measures with established markers of intelligence, researchers postulate theoretical models underlying these information-processing constructs. However, there is a lack of substantive evidence that these phenomena are as robust within the individual as has been proposed. The authors tested the properties of intraindividual parameters by asking participants (N = 179) to perform 10 elementary cognitive tasks (ECTs). Detailed analyses revealed that average performance parameters, extracted from these ECTs, behaved lawfully. However, up to 40% of participants failed to provide acceptable indices of intraindividual model fit. Similarly, intraindividual variability measures appeared less valid than previously suggested. The implications of these findings for cognitive and biological models of intelligence are discussed.     

Reaction time explains IQ's association with death

Lower IQ is associated with earlier death, but the cause of the relationship is unknown. In the present study, psychometric intelligence and reaction times were both significantly related to all-cause mortality in a representative sample of 898 people aged 56 years who were followed up with respect to survival until age 70. The association between IQ and mortality remained significant after adjusting for education, occupational social class, and smoking, all of which have been hypothesized as confounding variables. The effect of IQ on mortality was not significant after adjusting for reaction time, suggesting that reduced efficiency of information processing might link lower mental ability and earlier death. This new field of cognitive epidemiology provides arguably the strongest evidence for the importance of psychological factors in physical health and human survival. Finding the mechanisms that relate psychometric intelligence to mortality might help in formulating effective interventions to reduce inequalities in health.     

Effects of age and the relationship between response time measures and psychometric intelligence in younger adults

The major goal of the present study was to investigate the potential influence of age on the relationship among performance measures derived from a Hick reaction time task and general intelligence (psychometric g). Participants were 130 male and 130 female younger adults (mean age: 24.6 years) covering a wide range of individual levels of intelligence. Results from structural-equation modelling analyses clearly indicate that there is no evidence for the notion of a general speed factor underlying psychometric g. A much more sufficient model is provided by the assumption that median reaction time (RTmd) and intraindividual variability of reaction time (RTSD), though highly correlated, reflect two distinct sources of variance for psychometric g. While age was negatively associated with RTmd, no such relationship could be established for RTSD.     

Simultaneous and successive syntheses and intelligence

Recent studies on information processing have developed an alternative model of mental abilities which constitutes an integration of Russian clinical research and North American factor analytic research. This model proposes that information may be processed in a simultaneous synthesis or a successive synthesis. The present study examines variations in these syntheses in three intelligence groups in order to identify the types of information processing characteristic of different intelligence groups. A stratified sampling of verbal and nonverbal IQ was used to select 60 boys of age 9–10 in each of three verbal IQ ranges: 71–90, 91–110, and 111–130. A battery of tests used in previous research was administered to all subjects. Multivariate analyses of variance and discriminant analyses indicated that the IQ groups differed markedly on tests used to identify simultaneous synthesis, most notably Raven's Progressive Matrices, and differed slightly less on tests of successive synthesis. Factor analyses of the test intercorrelations for each group revealed more factorial invariance across the IQ groups than had been suggested by a previous exploratory study. It was concluded that strong individual differences exist in simultaneous and successive syntheses over the major portion of the standardized intelligence range, and no high degree of specialization of information processing was characteristic of an intelligence group.     

Biomarkers, health, lifestyle, and demographic variables as correlates of reaction time performance in early, middle, and late adulthood

We aimed to identify demographic, health, and biomarker correlates of reaction time performance and to determine whether biomarkers explained age differences in reaction time performance. The sample comprised three representative cohorts aged 20-24, 40-44, and 60-64 years, including a total of 7,485 participants. Reaction time measures of intraindividual variability and latency were used. The measure of intraindividual variability used was independent of mean reaction time. Older adults were more variable than younger adults in choice reaction time performance but not simple reaction time performance. The most important correlates of reaction time performance after gender and education were biological markers such as forced expiratory volume at one second, grip strength, and vision. Few measures of physical or mental health or lifestyle were associated with poorer performance on reaction time measures. Biomarkers explained the majority of age-related variance in simple reaction time and a large proportion of variance in choice reaction time. We conclude that for the ages studied, biomarkers are more important than health factors for explaining age differences in reaction time performance.     

IQ change and occupational level: A longitudinal study with Third Harvard Growth Study participants

Eighty subjects from a larger number of participants in a longitudinal study were selected according to their 1916 Stanford-Binet Intelligence Test scores, administered in the 1930s, and their 1977 occupations. They were then individually administered the Wechsler Adult Intelligence Scale. The research questions asked were: Did subjects shift their positions relative to age peers with regard to measured intelligence from Time 1 (1930s) testing to Time 2 (1977) testing? And, if they did, were these shifts related to their occupational levels? A secondary question asked whether subjects as a group showed mean T score increments between test times. A Pearson correlation coefficient (r = .62) showed that subjects had significantly maintained their positions relative to peers with regard to measured intelligence over approximately one-half of a century. The hypothesis that persons in higher level occupations should show greater gains in measured intelligence over time was not supported. Using multiple regression procedures, no significant difference was found from analysis of effects of occupational level on D (D = T₂ ? T₁) scores. An 80-subject mean T score increase (M = +8.13) was found. This represented an average increase of four-fifths of a standard deviation in T score units. These data suggest that, on average, persons increase in mental abilities over time while maintaining IQ positions relative to peers and that those changes in IQ which do occur are not related to occupational level experience.     

儿童心理折叠能力的发展

本研究主要考察儿童心理折叠能力的发展。结果表明：（１）一般情况下,学生的心理折叠能力随年级（年龄）的上升而提高;（２）智力高的学生的心理折叠能力显著高于常态学生,而且,智力与年级之间存在较强的交互作用说明,智力是影响心理折叠能力发展的主要因素;（３）在本文所涉及的条件下,就总体而言,男生的心理折叠成绩高于女生。但这种性别差异主要不是来自常态组,而来自超常组;（４）不同被试组儿童的心理折叠能力具有不定全一致的发展曲线。     

Comparative judgments of animal intelligence and pleasantness

Symbolic comparisons of animal intelligence and pleasantness were investigated in five experiments using words and pictures as stimuli. Symbolic distance effects occurred in all experiments. Picture-word effects depended on the experimental design. Mean intelligence comparison reaction time (RT) did not differ for pictures and words when the pairs were presented to independent groups. With repeated measures, mean RT was faster for pictures than for words, but only on the second block of trials. This involved an asymmetrical transfer effect, so that word comparisons on the first trial block greatly facilitated picture comparisons on the second block, whereas picture comparisons did not facilitate subsequent word comparisons. Pleasantness comparisons showed a similar asymmetrical transfer pattern but differed from intelligence comparisons in that the mean RTs were faster with pictures than with words, even with an infinite item set and without prior exposure to the other class of material. The results are discussed in terms of dual coding and other models of symbolic comparisons.     

General intelligence,temperament, and the Matching Familiar Figures Test

To investigate the relationship between general intelligence g and temperament, highly intelligent 10-year-old children (N = 151) were compared with classmates of the same gender and socio-economic status but of average intelligence (N = 134). The two ability groups were administered the Matching Familiar Figures Test (MFFT) during home visits. The parents and teachers rated the temperament of the children. The results showed a consistent pattern: highly intelligent children are more task-oriented, e.g. less distractible and more controlled than their average counterparts. In the MFFT, gifted children not only gave a higher percentage of correct answers, but also showed longer (!) reaction times.     

There are stable individual differences in performance variability, both from moment to moment and from day to day

Individual differences in decision speed have been regarded as direct reflections of a "primitive" functional neurophysiological characteristic, which affects performance on all cognitive tasks and so may be regarded as the "biological basis of intelligence", or of age-related changes in mental abilities. More detailed analyses show that variability within an experimental session (WSV) is a stable individual difference characteristic and that mean choice reaction times (CRTs) are gross summary statistics that reflect variability, rather than maximum speed of performance. A total of 98 people aged from 60 to 80 years completed 36 weekly sessions on six different letter categorization tasks. After effects of practice and of circadian variability had been eliminated, individuals with lower scores on the Cattell Culture Fair intelligence test had slower CRTs and greater WSV on all tasks. A simulation study showed that the greater WSVs of low Cattell scorers led directly to the significantly greater variability of their mean CRTs from session to session. However because CRTs on tasks co-varied from session to session it was apparent that, besides being affected by WSV, individuals' between-session variabilities (BSVs) also vary because of state changes that affect their performance from day to day. It seems that both variability in performance from trial to trial during a session and variability in average performance from day to day are correlated, stable, individual difference characteristics that vary inversely with intelligence test performance. Methodological consequences of these results for interpretations of age-related cognitive changes, for variability between as well as within individuals, for individual differences in decision speed, and for circadian variability in performance are discussed.     

Memory and intelligence: Age and ability differences in strategies and organization of recall

Proficiency at organizing information for recall is one aspect of memory functioning which could be expected to be related to intelligence, or general ability. Comparisons of children of average and of superior ability (Kuhlmann-Anderson scores) in a multitrial free-recall learning task confirmed this prediction: Both level of recall and amount of sequential organization were significantly higher for the superior ability groups. Mental age definitions of intelligence imply that equivalent performance by children of different chronological ages will be based on qualitatively similar cognitive processes. This assumption was not confirmed. Age-related changes in mnemonic strategies were not associated with ability-related differences in recall or organization. Some features of memory development are more dependent on age, whereas others are more dependent on ability. The latter may be best explained in terms of production inefficiency (Flavell, 1970).     

Racial differences in intelligence: The importance of the executive system

The race-IQ controversy arose at a time when psychometric views of intelligence dominated. Little attention was paid to more process-oriented models in spite of the fact they provide alternative perspectives on the causes of individual differences in problem-solving. We hypothesized that much of the IQ spread commonly observed between black and white children can be attributed to differences in components of their executive systems, including the knowledge base, control processes, and metacognitive states. To test this possibility, black and white children who differed significantly on fluid and crystallized intelligence were tested on multiple tasks reflecting components of the executive systems as well as on perceptual efficiency tasks. Striking group differences were observed in metamemory, stragegy use, and general knowledge, but few reliable differences were found in perceptual efficiency. Regression analyses showed that different factors predicted fluid and crystallized intelligence, with metamemory predicting the latter but not the former. An implication of these findings has potential educational significance: training directed at executive skills, introduce at an early age, might elevate learning and problem-solving skills in black children, thereby reducing racial differences in crystallized intelligence.     

Sex differences in reaction time mean and intraindividual variability across the life span

Men are often found to have faster and less variable reaction times (RTs) than do women. However, it has not been established whether these differences occur in children. One suggestion is that sex differences in RT variability may be due to the effect of sex hormones on the brain and, by implication, may be expected in adults but not in children. The present study investigates sex differences in RT mean and intraindividual variability in a sample that includes both children and adults (age range = 4-75 years). Mean and intraindividual variability of simple RT (SRT) and 4-choice RT (CRT) were measured in 1,994 visitors to science festivals held in Edinburgh, Scotland, in 2008 and 2009 and in Cheltenham and Cambridge, England, in 2008. The commonly reported pattern of decreasing RT mean and variability in childhood and adolescence, followed by an increase in mean and variability through adulthood and into old age, was confirmed. Greater intraindividual variability for females in SRT and CRT was observed in adults but not in children. Males had significantly faster mean SRT than did females across the life span, but there were no sex differences in mean CRT. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Identification of sensorimotor components accounting for individual variability in Zahlen–Verbindungs-Test (ZVT) performance

The Zahlen–Verbindungs-Test (ZVT) represents a highly feasible measure of information-processing speed that correlates quite highly with standard psychometric tests of intelligence. The present study was designed to identify specific stages of the sensorimotor processing system that may account for individual differences in overall variability of ZVT performance. For this purpose, ZVT, reaction time (RT), lateralized readiness potential (LRP), and electromyogram (EMG) measures were obtained in 48 female participants. While faster RT, smaller intraindividual variability in RT, shorter response-locked LRP and EMG latencies were associated with superior ZVT performance, speed of stimulus analysis, as reflected by stimulus-locked LRP latency, was unrelated to ZVT performance. Additional commonality analyses suggested a functional relationship between ZVT performance and the time course of central aspects of response organization rather than the time required for execution of the overt motor response. These findings provide converging evidence for the general notion of an association between speed of motor processing and intelligence.     

Stability and change in adult intelligence: 2. Simultaneous analysis of longitudinal means and covariance structures

We analyzed data on psychometric intelligence from the Seattle Longitudinal Study, simultaneously estimating longitudinal factors, their covariance structure, and their mean levels. Data on five Thurstone Primary Mental Abilities subtests were available for 412 adults, ages 22-70 at first test, who were tested three times at 7-year intervals. A previous longitudinal factor analysis had shown high stability of individual differences (covariance stability) in general intelligence for three adult age groups. We extended that model to estimate factor means. All three age groups showed high levels of covariance stability, but differed sharply in their mean profiles. The young group showed increasing levels of general intelligence, the middle-aged group had stable levels of intelligence, and the old group showed salient, approximately linear, decline. The patterns of stability in middle-age, followed by mean decline and high covariance stability in old age, suggest a normative developmental transition from a stability pattern to a decline pattern of general intelligence, with the inflection point occurring somewhere around age 60.     

The relationship between mental rotation and arithmetic: do number line estimation,working memory,or place-value concept matter?

Mental rotation is positively related to arithmetic ability; however, the mechanism underlying this relationship remains unclear. The possible roles of working memory, place-value concept, and number line estimation in the correlation between mental rotation and whole-number computation were investigated. One hundred and fifty-five first-grade students were tested to determine their mental rotation ability, arithmetic ability, and non-verbal intelligence. One year later, their working memory, place-value concept, number line estimation, and overall arithmetic ability were assessed. After controlling for age, gender, and prior arithmetic ability, we found that mental rotation uniquely predicted arithmetic ability after one year. Further mediation analyses demonstrated that number line estimation significantly mediated the relationship between mental rotation and arithmetic ability. In contrast, neither working memory nor place-value concept significantly mediated the relationship between mental rotation and arithmetic ability. This study highlights that mental number line estimation is the most important element explaining the influence of a dynamic spatial skill, that is, mental rotation, on arithmetic ability among young Chinese children.     

Is age kinder to the initially more able?: differential ageing of a verbal ability in the Healthy Old People in Edinburgh study

Studies that examine whether there is differential age-related decline in intelligence test scores according to initial cognitive status, social class and education are reviewed. We tested the differential ageing hypothesis which states that decline in ability scores over time will be lower in those with superior mental ability, more education and higher social class at the time of original testing. 387 healthy old people were tested at baseline and followed up 4 years later. The National Adult Reading Test (NART) was administered on both occasions. NART-estimated IQ fell by a mean of 2.1 points over 4 years (p<0.001). Subjects in higher social class categories had higher NART scores overall (p<0.001), and had smaller NART decrements over 4 years. Ex-professional and -secretarial groups fell by a mean of 1.4 points in this period, versus 3.2 points for skilled manual, semi-skilled and unskilled groups. In addition, those who fell more in NART were older (p=0.001), were less educated (p<0.001), and had lower NART (p<0.001) scores at baseline. In summary, those with higher baseline ability, in higher social class groups, with more education and who are younger are relatively protected from decline in this verbal ability with age. Possible mechanisms of differential decline in this verbal intelligence with age are discussed.