Steps to a formal analysis of the cognitive-energetic model of stress and human performance

Effects of Response Probability on Response Force in Simple RT

Response force (RF) was measured in a simple reaction time (RT) experiment varying response uncertainty by cuing the probability of the response on each trial. In all cases, RF decreased as response probability increased. The dependence of RF on response probability was insensitive to foreperiod length and to the use of loud auditory response signals, although the dependence of RT on response probability was sensitive to both of these manipulations. In combination with previous findings, these results provide evidence that RT and RF can be dissociated. We describe an extension of Näätanen's readiness model that can account for the effects of response probability on RF and RT. According to this model, the distance between motor activation and a threshold for action is relatively large when subjects are unprepared, and a large increment is needed to exceed this threshold, resulting in slow but foreceful responses. A possible neurophysiological implementation of this model is suggested.

Stochastic cascade processes as a model of multi-stage concurrent information processing

McClelland's (Psychol. Rev. 86 (1979) 287) influential cascade model of reaction time (RT) is often seen as an important explicitly formulated alternative to strictly serial models because some of its basic notions fit in with known characteristics of neural activation processes. A disadvantage is that it is an essentially deterministic model to which noise is added by across-trials parameter variability that is unrelated to the concept of cascaded activation propagation per se. We propose and analyze a general stochastic cascade model based on neural counting processes; within this framework we present a new process-oriented interpretation of McClelland's cascade activation equation. We then theoretically explain and numerically explore conditions under which the stochastic cascade model predicts additive vs. interactive mean RT effects, and compare them to known properties of McClelland's model. Some of these properties remain valid even within a stochastic neural counting formulation, while others reflect assumptions which are essentially unrelated to the concept of cascaded activation.

Additive factors analysis of reaction time with alphanumericals and line orientations as stimuli

Most additive factors method (AFM) analyses of choice reaction time (CRT) have used alphanumerics whereas tests of single process models have often used line length or line orientation. The suggestion is raised that commonly observed additive effects of variables on CRT might not apply to stimuli of the latter category. This would mean a severe limitation of the AFM in that the stage structure of choice reactions would be stimulus specific. The issue is addressed in two experiments. The first showed additive effects of stimulus quality and stimulus-response compatiblility for both alphanumerics and line orientations as stimuli. The second showed that for both stimulus categories the effect of stimulus quality was fully reflected in visual fixation time. Together the results argue against a single central process and favour a stage model of CRT.

The exhaustive additivity displayed by nitrous oxide has implications for cognitive-energetical theory

The cognitive-energetical approach, which relies on the discrete stage model of additive factors logic, asserts that basal energetical mechanisms such as arousal act via particular information processing stages. The anaesthetic gas nitrous oxide (N(2)O) produces additivity at four of the five perceptual and central stages, but its effect on the remaining stage, feature extraction, is unknown. We investigated this stage using 12 subjects who performed a visual oddball experiment in which two levels of stimulus quality, three levels of breathing mixture (air, 25% and N(2)O, 35%) and three levels of stimulus probability were combined factorially. Reaction time (RT) and P300 were collected simultaneously. The RT results showed additivity between N(2)O, stimulus quality and probability. P300 latency also showed additivity between N(2)O and stimulus quality. Since the discrete stage model cannot easily account for the exhaustive additivity displayed by N(2)O on perceptual and central stages, we performed a continuous cascade model simulation to determine whether it is better able to account for this phenomenon. We found that exhaustive additivity could be reproduced by adding a time delay to the activation rate of the first stage, which we interpreted as evidence that N(2)O causes slowing prior to stage processing. To account for these results, we propose a two-tiered energetical model in which a lower GABAergic reticular system (influenced by N(2)O) modulates the activity of upper 'arousal-like' multidimensional ascending thalamocortical systems. The applicability of this model to drugs such as the barbiturates, the benzodiazepines and ethanol, as well as the aging process, is discussed.

Intersensorische Erleichterung: Auch visuelle Begleitreize können die Reaktionszeit verkürzen

Zusammenfassung. Reaktionen auf ein visuelles Reaktionssignal werden beschleunigt, wenn gleichzeitig ein auditiver Begleitreiz dargeboten wird. Umgekehrt werden Reaktionen auf ein auditives Reaktionssignal durch einen visuellen Begleitreiz nicht beschleunigt. In der Literatur wird dieser asymmetrische Effekt mit einer unterschiedlichen Verarbeitung von visuellen und auditiven Begleitreizen erklärt (Arousal- und Vorbereitungshypothese). Wir untersuchten, ob diese Modalitätsasymmetrie auch dann auftritt, wenn Begleitreize ausreichend beachtet werden. In zwei Experimenten wurde durch eine Zusatzaufgabe sichergestellt, daß visuelle und auditive Begleitreize gleichermaßen beachtet werden. In Experiment 1 wurden neben der Reizmodalität die Intensität des Reaktionssignals und des Begleitreizes und in Experiment 2 der zeitliche Abstand zwischen Reaktionssignal und Begleitreiz variiert. Gemessen wurden Reaktionszeit und Reaktionskraft. In beiden Experimenten konnte ein Erleichterungseffekt für visuelle und auditive Begleitreize nachgewiesen werden. Insbesondere die Analyse der Reaktionskraft legt die Annahme nahe, daß sowohl auditive als auch visuelle Begleitreize unspezifische Aktivität erzeugen und so die Reaktion beschleunigen. Diese Aktivität wird vermutlich direkt an das motorische System geleitet.

Effects of auditory stimulus intensity on response force in simple, go/no-go, and choice RT tasks

In four experiments, increasing the intensities of both relevant and irrelevant auditory stimuli was found to increase response force (RF) in simple, go/no-go, and choice reaction time (RT) tasks. These results raise problems for models that localize the effects of auditory intensity on purely perceptual processes, indicating instead that intensity also affects motor output processes under many circumstances. In Experiment 1, simple RT, go/no-go, and choice RT tasks were compared, using the same stimuli for all tasks. Auditory stimulus intensity affected both RT and RF, and these effects were not modulated by task. In Experiments 2-4, an irrelevant auditory accessory stimulus accompanied a relevant visual stimulus, and the go/no-go and choice tasks were used. The intensity of the irrelevant auditory accessory stimulus was found to affect RT and RF, although the sizes of these effects depended somewhat on the temporal predictability of the accessory stimulus.

Response force is sensitive to the temporal uncertainty of response stimuli

Three experiments examined whether temporal uncertainty about the delivery of a response stimulus affects response force in a simple reaction time (RT) situation. All experiments manipulated the foreperiod; that is, the interval between a warning signal and the response stimulus. In the constant condition, foreperiod length was kept constant over a block of trials but changed from block to block. In the variable condition, foreperiod length varied randomly from trial to trial. A visual warning and response stimulus were used in Experiment 1; response force decreased with foreperiod length in the variable condition, but increased in the constant condition. This result is consistent with the hypothesis that responses are less forceful when the temporal occurrence of the response stimulus is predictable. In a second experiment with an auditory warning signal and a response stimulus, response force was less sensitive to foreperiod manipulations. The third experiment manipulated both the modality and the intensity of the response signal and employed a tactile warning signal. This experiment indicated that neither the modality nor the intensity of the response signal affects the relation between response force and foreperiod length. An extension of Näätänen's (1971) motor-readiness model accounts for the main results.

Psychophysiological aspects of selective and divided attention during continuous manual tracking

Central, autonomic, and metabolic physiological measures were observed concurrently along with performance and subjective measures to compare the effects of tracking task difficulty during selective and divided attention. Eighteen dextral males performed visual compensatory manual tracking as a primary task while attending to or ignoring secondary-task auditory oddball stimuli. The difficulty of the tracking task was varied factorially by requiring participants to track with acceleration (second-order) or velocity (first-order) control and high or low bandwidth sum-of-sines disturbance. Tracking performance was affected by the difficulty manipulations but not by the attention manipulation. Event-related brain potential P300 amplitude to oddball target stimuli was sensitive to the division of attention and tracking order-of-control but not to tracking disturbance bandwidth when the oddball task was attended. Oxygen consumption, a measure of aerobic metabolism, was greater during acceleration than velocity tracking; however, cardiac measures were sensitive only to the division of attention. The results demonstrate that the attention and the task difficulty manipulations have physiologically dissociable effects that were interpreted as supporting a cognitive/energetic model of attention.

Testing the global-slowing hypothesis: are alcohol's effects on human performance process-specific or task-general?

In an interesting recent meta-analysis, Maylor and Rabbitt (1993) suggested that alcohol's effects on human performance may not be process- or stage-specific, but reflect a general, undifferentiated, cognitive slowing. According to this view, performance is globally slowed by a constant multiplicative fraction (b), such that the longer a process takes without alcohol on board (a -), the more it will be slowed by alcohol (a +). In summary: RTa+ = b b (RTa-). In this sense, the effects of alcohol are determined simply by the duration of a process or stage--not by its function or content--and attempts to map the effects of alcohol to specific cognitive operations are essentially futile. This global-slowing hypothesis entails, then, (i) that the function relating RTa+ to RTa- will be linear and increasing; (ii) that the value of b will be significantly greater than 1.0; and (iii) that all experimental factors which increase the complexity (hence, duration) of a task or stage will interact with alcohol. In this study we tested the global-slowing hypothesis directly using fixed set, varied set and concurrent sets item-recognition paradigms. All three tasks showed convincing additivity between alcohol and other key experimental factors which affect response latency (e.g., setsize, response type); there was no hint of any of the spectrum of significant interactions predicted by the global-slowing hypothesis. A meta-analysis of varied set latencies, analogous to Maylor and Rabbitt's, yielded a reasonably linear alcohol/no-alcohol function, but with a slope constant (b) less than 1.0. In all, the data provided little support for the global-slowing hypothesis.

Overlapping stage models and reaction time additivity: effects of the activation equation

Many experimental factors have been found to affect mean reaction time (RT) additively in factorial experiments. What sorts of RT models are compatible with this fact? Sternberg (1969) showed that serial, discrete-stage models are consistent with additivity, and as a result additivity has sometimes been regarded as evidence in favor of such models. However, McClelland (1979) showed that an alternative "cascade" model, which violates crucial assumptions of discrete-stage models, also predicts RT additivity in many cases. This article examines various modified versions of the cascade model, and shows that mean RT additivity arises from many overlapping stage models, including some with thresholds, information quantization, and nonlinear activation transformations. This suggests that other aspects of the data besides mean RT additivity should be examined to distinguish between serial and overlapping stage models.

On the discrimination between global and local trend hypotheses of life-span changes in processing speed

Meta-analyses of age effects on processing speed suggest a single, global mechanism underlying developmental speeding and slowing in the elderly. Myerson, Hale, Wagstaff, Poon and Smith (1990) proposed an information loss model assuming that a constant amount of information is lost at each processing step in all age groups whereas the rate of information loss differs between age groups. In this study, a series of simulations has been conducted comparing global versus local information loss. This has been outcomes of these deterministic and stochastic varieties of the information loss model. The outcomes of these comparisons were consistently negative; the information loss model fails to discriminate between global and local age effects on the reaction process. The simulations were followed by a discussion of Hohle's (1967) scheme for investigating selective age effects on processing speed. It was concluded that the combined approach of stage and distribution analysis of the reaction process augmented with psychophysiological time markers provides a powerful tool for the study of life-span changes in processing speed.

Controlled processing and vigilance in hyperactivity: time will tell

This paper reviews the concept of sustained attention, placing it within a theoretical framework in which deficits of attention are conceived of as deficits of controlled information processing. Two types of deficit of sustained attention are distinguished: perceptual sensitivity and perceptual criterion. These two deficits are linked to a model of human performance that links controlled processes to the energetic pools: arousal and activation. Perceptual sensitivity (d') deficits are said to reflect arousal deficiencies, especially when observed in the early period of a vigil. Perceptual criterion deficits are associated with the activation pool and the response criterion measure beta. Despite clear evidence of perceptual deficiency in the hyperactive children to a greater extent than in the control group, and that performance in d' declined with time on task, a significant interaction failed to occur between group classification and time on task. Thus, the results failed to support the hypothesis of a sustained attention deficit in hyperactives, since if hyperactives have a sustained attention deficit, both d' and beta should have shown a significantly greater decline in the hyperactive group than in the controls with time on task.