Effects of priming, discriminability, and reinforcement on reaction-time components of pigeon visual search

Pigeons searched computer screens for 1 of 4 letter targets among 55 alphanumeric distractors. In Experiment 1, valid-cue trials used distinctive patterns to signal the subsequent appearance of specific targets, whereas ambiguous-cue trials used a signal common to all targets. Search reaction times (RTs) after valid cues were shorter than after the ambiguous cue; increased target discriminability also reduced RT. In Experiment 2, when reinforcement for 2 targets shifted from 10% to 20%, RTs to those targets dropped, whereas RTs to the other 2 targets rose. RT distributions suggested that precues and discriminability both affect the momentary probability of finding a target, as embodied in the decay constant of an underlying exponentially distributed RT component. Reinforcement changes appeared to affect different components of the response process, embodied in changes in the mean of an underlying lognormal distribution.     

Reaction time and intelligence in the mentally retarted

Mildly retarted young adults were given simple and choice reaction time (RT) tests. Scores were also obtained on the Raven Progressive Matrices and the Figure Copying Test. Subjects' RTs increased as a function of stimulus complexity, and they were consistently subjects' intraindividual variability of response time was also markedly greater than that of non-retarded subjects. A number of RT parameters were found to be related to the measures of intelligence. Subjects seen on ten successive days showed low day-to-day stability of RT but no practice or fatigue effect.     

Age, information processing speed, and intelligence

Two parallel, but independent, literatures have grown out of observations that individual differences in information processing speed, as expressed in performance on choice reaction time (C RT) tasks, modestly correlate with individual differences in age and IQ test performance. These associations have prompted theories that individual differences in information processing speed functionally determine individual differences in performance of all cognitive skills by people of different general intellectual ability (Eysenck, 1986; Jensen, 1985) or age (Salthouse, 1982, 1985).

The experiments on which this literature has been based suffer from methodological weaknesses, such that comparisons have only been made very early in practice and have only concerned mean latencies for correct responses. An experiment compared 90 volunteers aged from 50 through 79 years who were grouped in terms of their performance on the AH 4 (Heim, 1968) IQ test. It explored the joint and independent effects of individual differences in age and in IQ test score and the effects of practice on mean latencies (C RTs) on the shapes of distributions of correct and incorrect responses and on the limiting speeds with which accurate responses can be made (speed/error trade-off functions). We suggest that a plausible explanation for the results is that individual differences in age and in general ability influence C RTs mainly because they affect the efficiency with which responses can be controlled to maximize speed while maintaining accuracy.     

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.     

Paced and self-paced continuous reaction time

Studies of the effect of pacing in continuous RT tasks are inconclusive. They have failed to (1) compare paced and self-paced RT at matched error rates and (2) examine RT distributions as well as mean or median RT. In the present experiment RTs were corrected for error rate by relating them to the speed-accuracy tradeoff function, which was measured in each experimental session. In this way deciles of the RT distributions of paced and self-paced conditions were compared, for eight subjects and four successive sessions. The task was a four-choice continuous RT task, employing visual stimuli. The results show that RT distributions are wider in the paced conditions. RTs of the first deciles are faster for pacing whereas medians in paced and self-paced conditions are about equal. The results can be explained when it is assumed that the variable R-S intervals in paced conditions lead to a larger variability of RT.     

Rate of processing and judgment of response speed: comparing the effects of alcohol and practice

Both alcohol and practice affect choice reaction time. The present study was conducted to investigate the possibility that impairment from alcohol and improvement with practice could be attributed to changes in the efficiency of control mechanisms (Rabbitt, 1979a), some of which depend upon the ability to judge response speed accurately. Twenty subjects participated in a four-choice reaction time experiment in which they received no alcohol (NA) in Session 1 and either no alcohol (10 subjects) or 0.8 ml alcohol (A) per kilogram of body weight (10 subjects) in Session 2. The task was to respond as fast and as accurately as possible to each stimulus. In addition, subjects were required to press a fifth key after any response that they considered to be both fast and accurate. Subjects had no difficulty in performing this task: (1) there was a significant difference of 122 msec between the mean response time for correct responses indicated as fast and that for correct responses not indicated as fast, and (2) subjects indicated 1 in 4 correct responses but only 1 in 64 errors. Alcohol increased all response times by approximately 40 msec. In contrast, practice decreased response times less for correct responses not indicated as fast than for correct responses indicated as fast. The ability to distinguish between fast and slow responses was thus unaffected by alcohol, but was improved by practice. Responses indicated as "fast" were significantly faster than errors, and appeared to occur without warning (unlike errors, which tended to end a sequence of increasingly fast correct responses). The results suggest that alcohol and practice influence choice reaction time in qualitatively different ways: Alcohol impairs overall response speed but has no effect on the ability to judge response speed, whereas practice improves both.     

Practice effects on fractionated response time related to age and activity level

Two days of practice on simple and choice reaction (RT) and movement time (MT) were studied using 60 males placed into four groups based upon age and physical activity level. Practice effects upon simple and choice RTs were different for young and old groups. Only the two inactive groups improved on simple and choice MT, with greatest improvement occurring on simple MT. Old Actives had true-score variance than the Old Inactives, but much greater than the two young groups. Intraindividual variability was greater for the two older groups even in the absence of practice effects. Results support the claim that a life style or regular physical activity may lessen aging effects upon RT and MT as well as attenuating interindividual variability.     

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.     

Use of simple reaction time in motor programming studies: a reply to Klapp, Wyatt and Lingo

Following a more explicit explanation of the 1960 memory-drum theory and the reasons for using the simple (rather than choice) RT method in testing predictions based on it, the eight experiments utilizing large-scale precued arm movements constrained as to directional accuracy are reviewed. In all cases, increasing complexity of the movement consistently increased response latency; control RT levels agreed with well-established typical values for auditory and visual stimuli. Following practice the complexity effect leveled off, retaining a significant latency differential. Results from experiments varying duration of a held movement position (with movement minimal and complexity invariant) are not relevant to these studies.     

Backward crosstalk effects in psychological refractory period paradigms: effects of second-task response types on first-task response latencies

Three experiments using psychological refractory period (PRP) tasks documented backward crosstalk effects in which the nature of the second-task response influenced the first-task response latencies. Such effects are difficult to explain within currently popular bottleneck models, according to which second-task response selection does not begin until first-task response selection has finished. In Experiments 1 and 2, the first of the PRP tasks required a choice reaction time (RT) response, whereas the second task required a go/no-go decision. Task 1 responses were faster when the second task required a go response than when it required a no-go response. Experiment 3 showed that Task 1 RTs were also influenced by the complexity of second-task responses. These backward crosstalk effects indicate that significant second-task processing is carried out in time to influence first-task responses and thus challenge strictly serial bottleneck models.     

The linear transformation model with frailties for the analysis of item response times

The item response times (RTs) collected from computerized testing represent an underutilized source of information about items and examinees. In addition to knowing the examinees’ responses to each item, we can investigate the amount of time examinees spend on each item. In this paper, we propose a semi‐parametric model for RTs, the linear transformation model with a latent speed covariate, which combines the flexibility of non‐parametric modelling and the brevity as well as interpretability of parametric modelling. In this new model, the RTs, after some non‐parametric monotone transformation, become a linear model with latent speed as covariate plus an error term. The distribution of the error term implicitly defines the relationship between the RT and examinees’ latent speeds; whereas the non‐parametric transformation is able to describe various shapes of RT distributions. The linear transformation model represents a rich family of models that includes the Cox proportional hazards model, the Box–Cox normal model, and many other models as special cases. This new model is embedded in a hierarchical framework so that both RTs and responses are modelled simultaneously. A two‐stage estimation method is proposed. In the first stage, the Markov chain Monte Carlo method is employed to estimate the parametric part of the model. In the second stage, an estimating equation method with a recursive algorithm is adopted to estimate the non‐parametric transformation. Applicability of the new model is demonstrated with a simulation study and a real data application. Finally, methods to evaluate the model fit are suggested.     

Word frequency, repetition, and lexicality effects in word recognition tasks: beyond measures of central tendency

Response time (RT) distributions obtained from 3 word recognition experiments were analyzed by fitting an ex-Gaussian function to the empirical data to determine the main effects and interactive influences of word frequency, repetition, and lexicality on the nature of the underlying distributions. The ex-Gaussian analysis allows one to determine if a manipulation simply shifts the response time (RT) distribution, produces a skewing of the RT distribution, or both. In contrast to naming performance, the lexical decision results indicated that the main effects and interactions of word frequency, repetition, and lexicality primarily reflect increased skewing of the RT distributions, as opposed to simple shifts of the RT distributions. The implications of the results were interpreted within a hybrid 2-stage model of lexical decision performance.     

GLOBAL PROCESSING-TIME COEFFICIENTS CHARACTERIZE INDIVIDUAL AND GROUP DIFFERENCES IN COGNITIVE SPEED

Abstract— Forty participants performed seven different information processing tasks (choice reaction time, letter classification, visual search, abstract matching, line-length discrimination, mental rotation, and mental paper-folding) Slow (top quartile) and fast (bottom quartile) processors were selected based on their mean z scores Response times (RTs) of the slow and fast groups in the 21 conditions of the seven tasks were linear functions of the mean RTs of the entire group (both r²s = 99) In addition, individuals' RTs were well described by linear functions (median r²= 93) When tasks were ranked in order of complexity, the odd-even reliability of the ratio of an individual's RT to the average RT was 80, indicating that such ratios remain relatively stable across tasks Taken together, these findings indicate that the performance of an individual on diverse tasks can be predicted on the basis of a single processing-time coefficient Such coefficients may provide useful indices of the efficiency with which different individuals process information     

Lateral stimulus-response compatibility effects in the oculomotor system.

Eye movement reaction time (RT) was measured in simple and choice RT situations in which monaural tones were presented to the left or right ear. In the choice RT conditions, tones of one frequency signaled a left looking response and tones of another frequency signaled a right looking response. In the simple RT condition, tones were presented in 2 blocks signaling right or left looking responses. RTs were measured by electro-oculogram (EOG), with electrodes placed over the outer canthus of each eye. In the choice RT condition, oculomotor RTs were faster when the tones signaling right or left looking were presented in the ears corresponding to the direction of looking than when they occured in the opposite ear. No such correspondence was present in the simple RT condition. Ss also performed a manual choice RT task. The lateral stimulus- response (S-R) compatibility effects obtained confirmed previous findings and were of the same magnitude as those obtained in the oculomotor response modality. Asymmetry in correlations between oculomotor and manual compatibility effects suggests differential hemispheric mediation.     

A crossed random effects diffusion model for speeded semantic categorization decisions

Choice reaction times (RTs) are often used as a proxy measure of typicality in semantic categorization studies. However, other item properties have been linked to choice RTs as well. We apply a tailored process model of choice RT to a speeded semantic categorization task in order to deconfound different sources of variability in RT. Our model is based on a diffusion model of choice RT, extended to include crossed random effects (of items and participants). This model retains the interesting process interpretation of the diffusion model’s parameters, but it can be applied to choice RTs even in the case where there are few or no repeated measurements of each participant-item combination. Different aspects of the response process are then linked to different types of item properties. A typicality measure turns out to predict the rate of information uptake, while a lexicographic measure predicts the stimulus encoding time. Accessibility measures cannot reliably predict any component of the decision process.     

Verbal predictions of unexpected stimuli and choice reaction time

In two choice reaction time (RT) experiments, subjects verbally predicted the stimulus alternative that was either most or least likely to be presented on each trial. An expectancy interpretation of prediction effects requires that stimuli matching least likely predictions yield the longest RTs. In Experiment 1, with four stimulus alternatives, RTs to stimuli matching the verbalized stimulus, both most likely and least likely predictions, were shorter than RTs to stimuli that matched neither the most nor the least likely predictions. However, matching most likely predictions produced faster responses with two alternatives. In Experiment 2, multiple predictions of both most and least likely stimuli were compared with joint predictions of first and second most likely alternatives. RTs to stimuli matching least likely predictions were longer than RTs to most likely matches, implicating prediction type as a partial determinant of RT. Matching least likely stimuli were responded to more quickly than unpredicted alternatives, demonstrating the importance of generating a prediction per se over the implied level of expectancy. Results from both experiments were contrasted with nonparametric predictions from an ordered memory scanning model.     

Reaction Time Distribution Analysis of Neuropsychological Performance in an ADHD Sample

Differences in reaction time (RT) variability have been documented between children with and without Attention Deficit Hyperactivity Disorder (ADHD). Most previous research has utilized estimates of normal distributions to examine variability. Using a nontraditional approach, the present study evaluated RT distributions on the Conners’ Continuous Performance Test in children and adolescents from the Multimodal Treatment Study of ADHD sample compared to a matched sample of normal controls (n = 65 pairs). The ex-Gaussian curve was used to model RT and RT variability. Children with ADHD demonstrated faster RT associated with the normal portion of the curve and a greater proportion of abnormally slow responses associated with the exponential portion of the curve. These results contradict previous interpretation that children with ADHD have slower than normal responding and demonstrate why slower RT is found when estimates of variability assume normal Gaussian distributions. Further, results of this study suggest that the greater number of abnormally long RTs of children with ADHD reflect attentional lapses on some but not all trials.     

Consciousness of attention and expectancy as reflected in event-related potentials and reaction times

The effects of conscious expectancies and attention on event-related potentials (ERP) and choice reaction times (RT) and their modulation by stimulus sequence were studied. Subjects retrospectively reported their expectancy of, and attention to, the terminal tones of short series. ERPs and RTs showed the usual sequential effects that were modulated by practice. As ratings were affected by only a few of the stimulus sequence, conscious access to sequence-based expectancy or attention appears to be fragmentary. Increased P300 amplitude with attention indicates conscious access to processing capacity. RTs and P300 latencies suggest stimulus processing time to decrease with sequence-based and consciously accessible expectancy. Differential effects of stimulus sequences and conscious expectancies on P300 amplitude indicate influences of two varieties of expectancy.     

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.     

Effect of moderate doses of alcohol on simple auditory reaction time in a vigilance setting

An experiment was performed with 11 voluntary male subjects to test the effects of moderate doses of alcohol on simple auditory RT in a vigilance setting. Subjects were tested during a 30-min. session, during which signals were presented with an average intersignal interval of 3.75 sec. Subjects responded by pressing a microswitch held in the preferred hand. Analysis indicated that absolute means increased as a function of alcohol dose. With time-on-task alcohol produced a faster increase in RT and especially affected the longest RTs. Number of extreme long reactions (blockings) and mean duration of these reactions increased under alcohol and were directly related to time on task; alcohol produced a much faster increase in number of blockings with time on task. Results were discussed in terms of attentional processes and habituation theory. Some practical implications of the results were pointed out.