The attentional demands of encoding and retrieval in younger and older adults: 2. Evidence from secondary task reaction time distributions

Three studies examined the effects of encoding or retrieval on properties of secondary task reaction time (RT) distributions in younger and older adults. Relative to full attention conditions, encoding and retrieval increased secondary task RT medians and standard deviations more for older adults than for younger adults, and the age-related RT increase was most pronounced among the slowest RTs. Hierarchical regression analyses revealed two age-related mechanisms underlying these effects, which were interpreted as cognitive slowing and reductions in attentional resources. Cognitive slowing affects the entire RT distribution regardless of the memory task. By contrast, reduced attentional resources result in very long RTs, especially when the tasks require self-initiated encoding or retrieval operations.     

Effects of amphetamine and barbiturate in a serial reaction task under paced and self-paced conditions.

Effects of drug conditions (barbiturate, amphetamine, placebo) were investigated in a serial choice RT-task under three pacing conditions: self-paced, paced-fast (approx. 3 signals/sec) and paced-slow (approx. 1 signal/sec). Drug treatment and pacing condition were varied in a factorial design with 9 male Ss. Drugs affected the reaction time but not the error scores. Barbiturate slowed down RT and this effect was most prominent in paced-fast. Amphetamine, on the other hand, speeded up the RT but it had no effect in paced-fast. To account for these differential effects of the two drugs, it was postulated that barbiturate counteracts the arousing effect of time pressure whereas amphetamine speeds up reaction when the task is not arousing. This is consistent with Trumbo and Gaillard (1975) but it contradicts predictions derived from a theory by Broadbent (1971).     

Effects of alcohol, practice, and task complexity on reaction time distributions.

The effects of alcohol (1.0 ml/kg body weight) and practice (2 sessions) were investigated in 2-, 4-, and 8-choice reaction time (RT) tasks with 24 male subjects. The number of errors increased with alcohol, practice, and increasing task complexity (choice). Mean RT decreased with practice, but increased with alcohol and complexity. Both the alcohol and practice effects on mean RT increased as complexity increased. The effects of alcohol, practice, and complexity were all larger for the higher percentiles of the RT distributions than for the lower percentiles. RT distributions were further analysed at each level of choice by plotting percentiles (5th, 10th, ... , 95th) for alcohol conditions against corresponding percentiles for no-alcohol conditions, and percentiles obtained early in practice (Session 1) against those obtained later in practice (Session 2). These plots revealed that whereas at all levels of choice the effect of alcohol could be expressed as a simple linear transformation of all RTs, the effect of practice required a more complex curvilinear transformation. Thus, alcohol produces a general slowing of all RTs, whereas practice produces a disproportionate improvement at the slower end of the RT distribution.     

Generative processes in character classification: Evidence for a probe encoding set

The role of rehearsal in a varied set memory scanning task was investigated by asking the subjects to rehearse subvocally the one to four target characters cyclically at a self-paced rate until the probe was presented. After making a manual positive or negative response to the probe, the subjects reported the last item rehearsed before the probe was presented. The results indicate that, when the last rehearsed item matched the probe, RTs were significantly faster than when it differed. Mean RTs over target set size were generally well fit by linearly increasing RT functions, with comparable slope values for negative responses and positive responses when the last rehearsal was the same as or different from the probe. The data suggest that rehearsal may reduce the duration of the probe encoding stage through some mechanism of pathway activation by providing the subject with a generated representation of what may appear next as a probe.     

After-effects of responding and of withholding responses in C.RT tasks

The effects of response repetition on choice RT were compared in b-reaction and in c-reaction tasks [Experiments I(a) and I(b)]. The difference in RTs for repeated and for non-repeated responses was found to be less for c-reaction than for b-reaction tasks. This seemed to be because in c-reaction tasks subjects can prepare themselves to make the same response on every trial, so that there is little further RT reduction consequent on immediate response repetition. In b-reaction tasks subjects cannot always prepare to make the same response, so that the difference between response repetition RT and responce alteration RT is greater. Experiment II examined transitions between events in a serial, self-paced C.RT task in which subjects made a different response to each of two signals but withheld any response to the onset of a third. In this task responses were faster when they followed other, different responses than when they followed “no go” trials. The results of these experiments allow us to reject, even for very elementary tasks, a simple “S--R connection network” model for the processes involved in the identification of signals and the production of responses to them.     

Inconsistency in serial choice decision and motor reaction times dissociate in younger and older adults

Intraindividual variability (inconsistency) in reaction time (RT) latencies was investigated in a group of younger (M=25.46 years) and older (M=69.29 years) men. Both groups performed 300 trials in 2-, 4-, and 8-choice RT conditions where RTs for decision and motor components of the task were recorded separately. A dissociation was evident in that inconsistency was greater in older adults for decision RTs when task demands relating to the number of choices and fatigue arising from time-on-task were high. For younger persons, a weak trend toward greater inconsistency in motor RTs was evident. The results are consistent with accounts suggesting that inconsistency in neurobiological mechanisms increases with age, and that attentional lapses or fluctuations in executive control contribute to RT inconsistency.     

The locus of the benefits of repetition-lag memory training

The current study examined the effects of responses on error-adjacent trials (i.e., those immediately preceding or following errors) on age differences in measures of intraindividual variability and the shape of response time (RT) distributions on a two-back task. Removing error-adjacent responses reduced variability as measured by the coefficient of variation, but did so similarly for younger and older adults. However, older adults’ standard deviations (SDs) were less than those of younger adults with comparable RTs, raising questions regarding the validity of the coefficient of variation. An ex-Gaussian analysis revealed that removing the RTs on error-adjacent trials reduced the length of the tails of distributions and the skewness of the distributions. These properties were reduced more for older adults than for younger adults. These results indicate that the influence of error-adjacent trials should be considered when analyzing intraindividual variability and the shape of RT distributions to test theories of cognitive aging.     

A comparison of sequential sampling models for two-choice reaction time

The authors evaluated 4 sequential sampling models for 2-choice decisions--the Wiener diffusion, Ornstein-Uhlenbeck (OU) diffusion, accumulator, and Poisson counter models--by fitting them to the response time (RT) distributions and accuracy data from 3 experiments. Each of the models was augmented with assumptions of variability across trials in the rate of accumulation of evidence from stimuli, the values of response criteria, and the value of base RT across trials. Although there was substantial model mimicry, empirical conditions were identified under which the models make discriminably different predictions. The best accounts of the data were provided by the Wiener diffusion model, the OU model with small-to-moderate decay, and the accumulator model with long-tailed (exponential) distributions of criteria, although the last was unable to produce error RTs shorter than correct RTs. The relationship between these models and 3 recent, neurally inspired models was also examined.     

The Effect of Cane Use on Attentional Demands During Walking

We investigated the effects of cane use, lateral walking stability, and cane use practice on attentional demands during walking. Attentional demands were assessed using dual-task methodology with a reaction time (RT) task. Sixteen healthy young subjects performed the RT task during walking, before and after cane use practice under four conditions: with/without cane use while wearing normal/unstable shoes. Among normal shoe conditions, cane use resulted in longer RTs. In contrast, RTs were similar regardless of cane use in the unstable shoe conditions. Among conditions without cane use, unstable shoes resulted in longer RTs. In contrast, RTs were similar regardless of shoe type in the cane use conditions. This study suggests that using a cane during walking requires additional attention; however, the resulting attentional demands depend on walking stability.     

Effects of personality, perceptual difficulty and pacing of a task on productivity, job satisfaction, and physiological stress

The relative psychological, physiological, and performance advantages and disadvantages of utilizing machine-paced and self-paced work were examined by having 12 subjects perform a marking-stapling task at 2 levels of perceptual difficulty and under 2 pacing conditions for 30 min. each. (a) 3 subjects who on the personality tests were identified as introverted, reserved, and trusting preferred to work in the machine-paced condition, while 9 subjects who were identified as extroverted, outgoing and suspicious preferred the self-paced condition, (b) the performance errors in machine-paced operation were 372% higher than for self-paced work, and (c) there were no differences between machine-paced and self-paced work on physiological variables, except for sinus arrhythmia for the task with high perceptual load, and quantity of production.     

A diffusion model decomposition of the practice effect

When people repeatedly perform the same cognitive task, their mean response times (RTs) invariably decrease. The mathematical function that best describes this decrease has been the subject of intense debate. Here, we seek a deeper understanding of the practice effect by simultaneously taking into account the changes in accuracy and in RT distributions with practice, both for correct and error responses. To this end, we used the Ratcliff diffusion model, a successful model of two-choice RTs that decomposes the effect of practice into its constituent psychological processes. Analyses of data from a 10,000-trial lexical decision task demonstrate that practice not only affects the speed of information processing, but also response caution, response bias, and peripheral processing time. We conclude that the practice effect consists of multiple subcomponents, and that it may be hazardous to abstract the interactive combination of these subcomponents in terms of a single output measure such as mean RT for correct responses. Supplemental materials may be downloaded from http://pbr .psychonomic-journals.org/content/supplemental.     

Ageing effects on the attention demands of walking

Attention demands of walking were determined in six male and six female young adults (mean 26.3 yr) and 12 gender-matched healthy, active older adults (mean 71.1 yr) using a dual task procedure with a reaction time (RT) secondary task. In three conditions an auditory stimulus, a visual stimulus and both stimuli (auditory/visual) were presented. Relative to no-walking baselines, increased RT was found in all conditions revealing an attentional cost of normal walking. When participants traversed the laboratory walkway and also positioned one of their feet within a target area on the ground, attention demands were greater than in unconstrained walking. In the targeting task, RTs to the visual stimulus were longer than for the auditory stimulus due to the interference associated with viewing both the stimulus monitor and the foot-target. Older participants' RTs in the visual and auditory/visual conditions, but not in the auditory condition, were significantly longer than for the young group in both walking tasks but RTs for young and older adults were not different in no-walking baseline trials. Inspection of mean RT functions at time intervals following gait initiation (0-3000 ms from the first step) suggested a fluctuating attentional cost of walking with increased demands associated with contingencies requiring step length regulation. The findings have applied significance in demonstrating the possibility of increased falls and pedestrian accident risk in older individuals in dual task situations such as road crossing.     

A mathematical model for paced serial addition

The paced serial addition task is reminiscent of a series of tasks studied in the later 1950s which were concerned with recall under conditions of pacing. The information processing operations in this task are completed in about a second and the paradigm allows a large amount of data to be collected in a short time. Group performance shows a primacy effect lasting a few seconds followed by a steady state. In this paper, a model is developed for steady-state performance consisting of continuous time and discrete components that generalize to a semi-Markov model. The model accounts for results from the two experiments presented and deviations of the model from the data point out distinct strategies being employed by the subject. The components of the model have direct psychological interpretation and allow many of the processes underlying performance to be specified.     

Are go/no-go tasks preferable to two-choice tasks in response time experiments with older adults?

Recent research has shown that, in response time (RT) tasks, the go/no-go response procedure produces faster (and less noisy) RTs and fewer errors than the two-choice response procedure in children, although these differences are substantially smaller in college-aged adults. Here we examined whether the go/no-go procedure can be preferred to the two-choice procedure in RT experiments with older adults (i.e. another population with slower and more error-prone responding than college-aged individuals). To that end, we compared these response procedures in two experiments with older adults (M_age?=?83 years): a visual word recognition task (lexical decision) and a perceptual task (numerosity discrimination). A group of young adults (M_age?=?31 years) served as a control. In the lexical decision experiment, results showed a go/no-go advantage in the mean RTs and in the error rates for words; however, this was not accompanied by less noisy RT data. The magnitude of the word-frequency effect was similar in the two response procedures. The numerosity discrimination experiment did not reveal any clear differences across response procedures, except that the RTs were noisier in the go/no-go procedure. Therefore, we found no compelling reasons why the go/no-go procedure should be preferred over the two-choice procedure in RT experiments with older adults.     

Concurrent guidance of attention by multiple working memory items: Behavioral and computational evidence

During visual search, task-relevant representations in visual working memory (VWM), known as attentional templates, are assumed to guide attention. A current debate concerns whether only one (Single-Item-Template hypothesis; SIT) or multiple (Multiple-Item-Template hypothesis; MIT) items can serve as attentional templates simultaneously. The current study was designed to test these two hypotheses. Participants memorized two colors, prior to a visual-search task in which the target and the distractor could match or not match the colors held in VWM. Robust attentional guidance was observed when one of the memory colors was presented as the target (reduced response times (RTs) on target-match trials) or the distractor (increased RTs on distractor-match trials). We constructed two drift-diffusion models that implemented the MIT and SIT hypotheses, which are similar in their predictions about overall RTs, but differ in their predictions about RTs on individual trials. Critically, simulated RT distributions and error rates revealed a better match of the MIT hypothesis to the observed data than the SIT hypothesis. Taken together, our findings provide behavioral and computational evidence for the concurrent guidance of attention by multiple items in VWM.

     

Three kinds of error-signalling responses in a serial choice task

During serial self-paced choice response tasks mean reaction times (RTs) for responses which are made in order to correct errors are faster than mean RTs for other correct responses. Experiment I showed that subjects can accurately correct errors in a four-choice task by making the response which they should have made, even though they are given no indication that an error has occurred. Experiment 2 showed that subjects correct their errors faster and more accurately when they use correction procedure than when they make a common response to all errors. The implication that subjects can correct errors because they know what response they should have made allows some comments on the constraints which must be met by various models which have been proposed to explain error-correction.     

Analysis of group differences in processing speed: Where are the models of processing?

Recently, Myerson, Adams, Hale, and Jenkins (2003) replied to arguments advanced by Ratcliff, Spieler, and McKoon (2000) about interpretations of Brinley functions. Myerson et al. (2003) focused on methodological and terminological issues, arguing that (1) Brinley functions are not quantile-quantile (QQ) plots of distributions of mean reaction times (RTs) across conditions; that the fact that the slope of a Brinley function is the ratio of the standard deviations of the two distributions of means has no implications for the use of slope as a measure of processing speed; that the ratio of slopes of RT functions for older and young subjects plotted against independent variables equals the Brinley function slope; and that speed-accuracy criterion effects do not account for slowing with age. We reply by showing that Brinley functions are plots of quantiles against quantiles; that the slope is best estimated by the ratio of standard deviations because there is variability in the distributions of mean RTs for both older and young subjects; that the interpretation of equality of the slopes Brinley functions and plots of RTs against independent variables in terms of processing speed is model dependent; and that speed-accuracy effects in some, but not all, experiments are solely responsible for Brinley slopes greater than 1. We conclude by reiterating the point that was not addressed in Myerson et al. (2003), that the goal of research should be modelbased accounts of processing that deal with correct and error RT distributions and accuracy.     

The costs of target prioritization and the external requirements for using a recall-to-reject strategy in memory exclusion tasks: a meta-analysis

In event-related potential (ERP) studies, the left-parietal old/new effect is commonly considered as a neural correlate of recollection. In memory exclusion tasks, the effect is usually observed when the targeted information is identified, but it is not necessarily present when studied items are rejected as nontargets. Interestingly, both the presence and the absence of such old/new effects to nontargets have been regarded as indicator for strategic retrieval. We reviewed previous ERP studies using memory exclusion tasks to analyze the reaction time (RT) pattern in such studies, as well as the influence of task difficulty on the occurrence of nontarget retrieval. We identified 44 test conditions, reported in 24 studies, and subjected the behavioral data to a meta-analysis. The RTs to correctly rejected new items were shorter than the RTs to hits, in particular in studies that required differentiating conceptual or perceptual information at test. When the retrieval of target information was prioritized, RTs to nontargets were delayed relative to targets. Without such prioritization, no such RT differences were observed. For test conditions with nontarget retrieval, the retrieval accuracy was poorer compared with test conditions without such retrieval. The findings support previous studies that claimed that nontarget retrieval becomes more likely when target retrieval is difficult, but the strong overlap in task difficulty between conditions with and without nontarget retrieval indicates that other, partly yet to-be-identified factors contribute to the occurrence of nontarget retrieval as well.     

Matching patterns vs matching digits: The effect of memory dependence and complexity on “same”-“different” reaction times

Two experiments are reported in which “same”-“different” reaction times (RTs) were collected to pairs of stimuli. In Experiment 1 stimuli were matrix patterns, and in Experiment 2 stimuli were digits. In both experiments, the pairs were presented simultaneously (discrimination task) and successively (memory task) for a set of nine simple and a set of nine complex stimuli. The following results were obtained: discrimination RTs were longer than memory RTs; RTs to complex stimuli were longer than RTs to simple stimuli; “same” RTs were faster than “different” RTs across all conditions except simple pattern discrimination, for which “different” RTs were faster than “same” RTs; and discrimination RTs for complex patterns were longer than would be predicted from the other conditions. Some evidence was obtained that the form of encoding for both patterns and digits in the memory task was visual. These results are discussed in terms of encoding and comparison strategies.     

Wholistic and analytic stimulus processing: The development of selective perceptual strategies

This experiment reports an investigation of the development of selective processing strategies as subjects become increasingly more practised at a serial self-paced RT task. It demonstrates the effect a preceding stimulus can have on the analysis of a current signal and the development of active analytic strategies in favour of passive wholistic processing, with practice. The stimuli used were letters with irrelevant visual noise dot patterns superimposed on them. The letter, or the dot pattern, or both, could be repeated on successive trials. Early in practice repetition of both stimulus components simultaneously produced short reponse latencies relative to repetition of the letter alone. The number of noise dots markedly affected RT. Late in practice, however, letter repetition RTs were small, irrespective of whether or not the noise dot pattern was repeated. Furthermore, the number of noise dots no longer had an effect on the RT to these stimulus transitions. The results suggest that subjects appear to be able to select relevant information to process as they become progressively more practised, even though there is evidence that they compare the current stimulus with an iconic representation of the immediately preceding one.