Age and individual differences in visuospatial processing speed: testing the magnification hypothesis

Replication and extension of the toolbox approach to measuring attention control

There is an increasing consensus among researchers that traditional attention tasks do not validly index the attentional mechanisms that they are often used to assess. We recently tested and validated several existing, modified, and new tasks and found that accuracy-based and adaptive tasks were more reliable and valid measures of attention control than traditional ones, which typically rely on speeded responding and/or contrast comparisons in the form of difference scores (Draheim et al. Journal of Experimental Psychology: General, 150(2), 242-275, 2021). With these improved measures, we found that attention control fully mediated the working memory capacity-fluid intelligence relationship, a novel finding that we argued has significant theoretical implications. The present study was both a follow-up and extension to this "toolbox approach" to measuring attention control. Here, we tested updated versions of several attention control tasks in a new dataset (N = 301) and found, with one exception, that these tasks remain strong indicators of attention control. The present study also replicated two important findings: (1) that attention control accounted for nearly all the variance in the relationship between working memory capacity and fluid intelligence, and (2) that the strong association found between attention control and other cognitive measures is not because the attention control tasks place strong demands on processing speed. These findings show that attention control can be measured as a reliable and valid individual differences construct, and that attention control shares substantial variance with other executive functions.

GIVE me your attention: Differentiating goal identification and goal execution components of the anti-saccade effect

The anti-saccade task is a commonly used method of assessing individual differences in cognitive control. It has been shown that a number of clinical disorders are characterised by increased anti-saccade cost. However, it remains unknown whether this reflects impaired goal identification or impaired goal execution, because, to date, no procedure has been developed to independently assess these two components of anti-saccade cost. The aim of the present study was to develop such an assessment task, which we term the Goal Identification Vs. Execution (GIVE) task. Fifty-one undergraduate students completed a conventional anti-saccade task, and our novel GIVE task. Our findings revealed that individual differences in anti-saccade goal identification costs and goal execution costs were uncorrelated, when assessed using the GIVE task, but both predicted unique variance in the conventional anti-saccade cost measure. These results confirm that the GIVE task is capable of independently assessing variation in the goal identification and goal execution components of the anti-saccade effect. We discuss how this newly introduced assessment procedure now can be employed to illuminate the specific basis of the increased anti-saccade cost that characterises various forms of clinical dysfunction.

Bridging the gap between different measures of the reading speed deficit in developmental dyslexia

The study assessed how decoding and pronunciation times contribute to total reading time in reading aloud and how these measures change in the presence of developmental dyslexia. Vocal reaction times (RTs), pronunciation times, and total reading times were measured while 25 children with dyslexia and 43 age-matched typically developing readers read singly presented words and non-words that varied for length. Group differences were large for vocal RTs; children with dyslexia were increasingly slower as a function of condition difficulty (over-additivity effect); lexicality and length influenced RTs even when over-additivity was controlled for by z-score transformation. The group differences were also large for vocal total reading times, but the effect of over-additivity was smaller than that of vocal RTs and no selective influence of lexicality and length was detected. Pronunciation times showed very small individual differences and no over-additivity effect; children with dyslexia were more sensitive to the effect of lexicality and length than controls. To assess the contribution of the cognitive and sensory-motor compartments in determining group differences, we applied the difference engine model. As for RTs, the relationship between means and standard deviations closely supported the prediction of a general cognitive delay in the slow group, with no group difference in the sensory-motor compartment. The variance in total reading times was predicted by combining the model results for RTs with the linear relationship between pronunciation times and task difficulty. The results help clarify the internal structure of reading times, a measure largely used in clinical testing to assess reading rate.

Toluene effects on the motor activity of adolescent, young-adult, middle-age and senescent male Brown Norway rats

Life stage is an important risk factor for toxicity. Children and aging adults, for example, are more susceptible to certain chemicals than are young adults. In comparison to children, relatively little is known about susceptibility in older adults. Additionally, few studies have compared toxicant susceptibility across a broad range of life stages. Results are presented for behavioral evaluations of male Brown Norway rats obtained as adolescents (1 month), or young (4 months), middle-age (12 months) and senescent (24 months) adults. Motor activity was evaluated in photocell devices during 30-min sessions. Age-related baseline characteristics and sensitivity to toluene (0, 300, 650, or 1000mg/kg, p.o.) were determined. In Experiment 1, young-adult, middle-age and senescent rats were treated with corn-oil vehicle before five weekly test sessions. Baselines of horizontal and vertical activity decreased with age, but each age-group's averages remained stable across weeks of testing. Baseline activity of older rats was more variable than that of the young adults; older rats were also more variable individually from week to week. Toluene (1000mg/kg) increased horizontal activity proportionately more in senescent rats (ca. 300% of control) than in middle-age or young-adult rats (ca.145-175% of control). Experiment 2 established toluene dose-effect functions in individual adolescent, young-adult, middle-age and senescent rats; each rat received all treatments, counterbalanced across four weekly sessions. Toluene produced dose-related increases in horizontal activity that increased proportionately with age. Experiment 3 replicated the effects of toluene (1000mg/kg) in Experiment 1, showing that toluene-induced increases in horizontal activity were greatest in the oldest rats. Collectively, the results show that aging increased susceptibility to toluene and also increased variability in toluene response. Given the rapid growth of the aged population, further research is needed on aging-related susceptibility to environmental contaminants.

Individual differences, intelligence, and behavior analysis

Despite its avowed goal of understanding individual behavior, the field of behavior analysis has largely ignored the determinants of consistent differences in level of performance among individuals. The present article discusses major findings in the study of individual differences in intelligence from the conceptual framework of a functional analysis of behavior. In addition to general intelligence, we discuss three other major aspects of behavior in which individuals differ: speed of processing, working memory, and the learning of three-term contingencies. Despite recent progress in our understanding of the relations among these aspects of behavior, numerous issues remain unresolved. Researchers need to determine which learning tasks predict individual differences in intelligence and which do not, and then identify the specific characteristics of these tasks that make such prediction possible.

The Model Human Processor and the older adult: parameter estimation and validation within a mobile phone task

The authors estimate weighted mean values for nine information processing parameters for older adults using the Card, Moran, and Newell (1983) Model Human Processor model. The authors validate a subset of these parameters by modeling two mobile phone tasks using two different phones and comparing model predictions to a sample of younger (N = 20; M-sub(age) = 20) and older (N = 20; M-sub(age) = 69) adults. Older adult models fit keystroke-level performance at the aggregate grain of analysis extremely well (R = 0.99) and produced equivalent fits to previously validated younger adult models. Critical path analyses highlighted points of poor design as a function of cognitive workload, hardware/software design, and user characteristics. The findings demonstrate that estimated older adult information processing parameters are valid for modeling purposes, can help designers understand age-related performance using existing interfaces, and may support the development of age-sensitive technologies.

Changes in saccadic reaction time while maintaining neck flexion in the elderly

We investigated changes in saccadic reaction time during maintenance of neck flexion in elderly individuals. Subjects comprised 49 volunteers, including 19 young adults and 30 elderly adults. Elderly subjects were separated into 2 groups (trained group: n=18; untrained group: n=12) based on responses to a questionnaire concerning activities of daily living. Saccadic reaction time was measured at angles of neck flexion of 0 degrees (resting position), 10 degrees and 20 degrees , with the chin either resting on a stand (chin-on) or not (chin-off). Reaction time was determined as the latency to the beginning of eye movement toward the lateral target, which was moved at random intervals in jumps of 20 degrees amplitude. In the chin-on posture, the angle of neck flexion had no significant effect on reaction time in any group. In the chin-off posture, the flexion angle significantly affected reaction time in both young and elderly trained groups. Significant shortenings of the reaction time were obtained at 10 degrees and 20 degrees neck flexion in the young group, and at 20 degrees neck flexion in the elderly trained group. No significant shortening of reaction time was noted in the elderly untrained group. These findings suggest that neural function associated with shortening of saccadic reaction time due to neck extensor activity decreases with age, and the decrements become more marked with inactivity in daily life.

Binding and inhibition in working memory: individual and age differences in short-term recognition

Two studies investigated the relationship between working memory capacity (WMC), adult age, and the resolution of conflict between familiarity and recollection in short-term recognition tasks. Experiment 1 showed a specific deficit of young adults with low WMC in rejecting intrusion probes (i.e., highly familiar probes) in a modified Sternberg task, which was similar to the deficit found in old adults in a parallel experiment (K. Oberauer, 2001). Experiment 2 generalized these results to 3 recognition paradigms (modified Sternberg, local recognition, and n back tasks). Old adults showed disproportional performance deficits on intrusion probes only in terms of reaction times, whereas young adults with low WMC showed them only in terms of errors. The generality of the effect across paradigms is more compatible with a deficit in content-context bindings subserving recollection than with a deficit in inhibition of irrelevant information in working memory. Structural equation models showed that WMC is related to the efficiency of recollection but not of familiarity.

Likelihood ratios: A simple and flexible statistic for empirical psychologists

Empirical studies in psychology typically employ null hypothesis significance testing to draw statistical inferences. We propose that likelihood ratios are a more straightforward alternative to this approach. Likelihood ratios provide a measure of the fit of two competing models; the statistic represents a direct comparison of the relative likelihood of the data, given the best fit of the two models. Likelihood ratios offer an intuitive, easily interpretable statistic that allows the researcher great flexibility in framing empirical arguments. In support of this position, we report the results of a survey of empirical articles in psychology, in which the common uses of statistics by empirical psychologists is examined. From the results of this survey, we show that likelihood ratios are able to serve all the important statistical needs of researchers in empirical psychology in a format that is more straightforward and easier to interpret than traditional inferential statistics.

Preserved neural correlates of priming in old age and dementia

Implicit memory, including priming, can be preserved in aging and dementia despite impairment of explicit memory. To explore the neural correlates of preserved memory ability, whole-brain functional MRI (fMRI) was used during a repetition priming paradigm to study 34 young adults, 33 older adults without dementia, and 24 older adults in the early stages of dementia of the Alzheimer type (DAT). Both older adult groups showed repetition-based response time benefits (priming) and changes in activation along inferior frontal gyrus similar to those shown by young adults. Across all three groups, repetition-related response time reductions correlated with prefrontal activity reductions, demonstrating a direct relation between priming and fMRI-measured activity change. These results suggest that despite difficulties with deliberate memory, both older adults without dementia and those with early-stage DAT can modify behavior mediated by prefrontal contributions, making these preserved abilities an attractive target for cognitive training and rehabilitation.

The difference engine: a model of diversity in speeded cognition

A theory of diversity in speeded cognition, the difference engine, is proposed, in which information processing is represented as a series of generic computational steps. Some individuals tend to perform all of these computations relatively quickly and other individuals tend to perform them all relatively slowly, reflecting the existence of a general cognitive speed factor, but the time required for response selection and execution is assumed to be independent of cognitive speed. The difference engine correctly predicts the positively accelerated form of the relation between diversity of performance, as measured by the standard deviation for the group, and task difficulty, as indexed by the mean response time (RT) for the group. In addition, the difference engine correctly predicts approximately linear relations between the RTs of any individual and average performance for the group, with the regression lines for fast individuals having slopes less than 1.0 (and positive intercepts) and the regression lines for slow individuals having slopes greater than 1.0 (and negative intercepts). Similar predictions are made for comparisons of slow, average, and fast subgroups, regardless of whether those subgroups are formed on the basis of differences in ability, age, or health status. These predictions are consistent with evidence from studies of healthy young and older adults as well as from studies of depressed and age-matched control groups.

Analysis of group differences in processing speed: Brinley plots, Q-Q plots, and other conspiracies

Researchers in a growing number of areas (including cognitive development, aging, and neuropsychology) use Brinley plots to compare the processing speed of different groups. Ratcliff, Spieler, and McKoon (2000) argued that a Brinley plot is a quantile-quantile (Q-Q) plot and that therefore Brinley plot regression slopes measure standard deviation ratios rather than relative speed of processing. We show that this argument is incorrect. Brinley plots, by definition, are not Q-Q plots; the former are based on unranked data and the latter are based on ranked data. Furthermore, the relationship between standard deviation ratios and slopes is a general property of regression lines and has no implications for the use of Brinley plot regression slopes as processing speed measures. We also show that the relative speed interpretation of Brinley plot slopes is strongly supported by converging evidence from a metaanalysis of visual search, mental rotation, and memory scanning in young and older adults. As to Ratcliff et al.'s hypothesis that age differences in response time are attributable to greater cautiousness on the part of the elderly, rather than true processing speed differences, this hypothesis has been extensively tested in previous studies and found wanting.

Cognitive construct measurement in small samples of younger and older adults: an example of verbal working memory

An important issue in experimental aging research is the accurate measurement of cognitive constructs, particularly in small-sample studies. Latent variable modeling approaches to assessing age-based construct similarity are difficult to implement in smaller-scale studies, which tend to have small samples and measurement of a single construct. We discuss factor score comparison methods for assessing age-based construct similarity that may be more appropriate for small-scale studies. We then examine these methods for a series of single-factor models of verbal working memory (VWM) based on data from three separate studies in which small samples of younger and older adults' completed VWM-based tasks. Our single-factor models accounted well for the associations among the sets of VWM tasks. This construct was also measured well across age groups and different samples. Our analyses suggest that factor score comparison methods may be useful for small-scale studies that require assessment of age-based measurement similarity in cognitive constructs.

Explicitly modeling the effects of aging on response time

Research into the effects of aging on response time has focused on Brinley plots. Brinley plots are constructed by plotting mean response times for older subjects against those for young subjects for a set of experimental conditions. The typical result is a straight line with a slope greater than 1 and a negative intercept. This linear function has been interpreted as showing that aging leads to a general slowing of cognitive processes. In this article, we show that the slope of the Brinley plot is actually a measure of the relative standard deviations of older versus young subjects' response times; it is not a measure of general slowing. We examine current models of the effects of aging on mean response time and show how they might be reinterpreted. We also show how a more comprehensive model, Ratcliff's diffusion model (1978), can account for Brinley plot regularities and, at the same time, provide an account of accuracy rates, the shapes of response time distributions, and the relative speeds of error and correct response times, aspects of the data about which models designed to account for Brinley plots are mute. We conclude by endorsing a research approach that applies explicit models to response time data in aging in order to use the parameters of the model to interpret the effects of aging.