Effects of graded doses of alcohol on speed-accuracy tradeoff in choice reaction time

The inconsistency of previous results concerning the effects of alcohol on reaction time (RT) may be related to possible tradeoffs between speed and accuracy. In the present experiment, complete speed-accuracy tradeoff functions were generated for each of five doses of alcohol (0-1.33 ml/kg) in a choice RT task. Such functions permit RT differences resulting from changes in performance efficiency to be distinguished from those due to changes in subjects’ speed accuracy criteria. Increasing doses of alcohol produced a progressive decrease in the slope parameter of linear equations fit to the speed-accuracy data, but did not significantly alter the intercept of the functions with the RT axis. Thus, alcohol reduced performance efficiency by decreasing the rate of growth of accuracy per unit time. A change in speed-accuracy criterion was combined with the decrease in efficiency at the highest alcohol dose.     

The effect of prediction accuracy on choice reaction time

In this study, we examined the effect of prediction accuracy on reaction time (RT). Subjects performed on three blocks of choice RT trials, all of which involved the mapping of four stimuli (red, green, 1, or 0) onto two response keys. The subjects were told that the four stimuli were equally probable and that their task was to respond to each stimulus onset by pressing the correct key. In one block (stimulus-prediction), the subjects predicted, prior to each trial, the precise stimulus that would appear. In a second block (category-prediction), the subjects predicted the category of the stimulus (i.e., color or digit) that would appear. In a third block (no-prediction), the subjects simply responded to each stimulus without making a prior prediction. In the stimulus-prediction block, RT was faster for correct predictions than for incorrect predictions. In addition, RT was faster on trials in which an incorrect prediction involved the correct category than on trials in which it involved the incorrect category: that is, a "half-wrong" prediction was better than an "all-wrong" prediction. In the category-prediction block, RT was faster when the stimulus category was predicted correctly than when it was not. There was little evidence of a response-facilitation contribution to the correct-prediction effect. These results permit inferences concerning the encoding and organization of information in memory.     

Independence of speed and accuracy in visual search: evidence for separate mechanisms.

Data from two studies that tested children's attention using visual search for a series of targets in a complex display and a sustained-attention task waiting for signals in a similar display were subjected to Factor Analysis to explore previous indications that speed and accuracy (the number of false alarms to nontargets) on this task reflect different mechanisms. The two factors identified confirmed the separation of these two measures and also suggested that the speed factor was related to Mental Age, while the accuracy factor was related to ratings of attentional ability. It is suggested that ratings of attentional ability reflect the efficiency of executive functions, displayed in the ability to inhibit responses to nontargets in these tasks, while speed of search is related to processing speed in the nervous system. Therefore intelligence and attentional ability depend on different underlying features of the nervous system.     

Effects of speed and accuracy instructions on performance in a visual search task by children with good or poor attention

Children rated by teachers as having good or poor attention ability carried out a visual search task in which they were required to find a series of targets in a complex display. Different groups were told to concentrate on either speed or accuracy. Previous studies using this task have consistently shown that children rated as having poor attention make more errors (false alarms to non‐targets in the display), but do not differ in the time to make a correct response; this result was replicated. Though the instructions produced wide differences in speed and error rates in the expected directions, these differences were similar in both attention groups and the differences in error rates between the two groups remained unchanged. It is suggested that these findings are not compatible with the view that children with poor attention make errors primarily due to fast impulsive responding, nor with an explanation in terms of slower processing of the input by such children. An alternative explanation of the high error rates in such children is offered in terms of weak executive function resulting in poor ability to inhibit false alarms to non‐targets.     

Determining subprocesses of visual feature search with reaction time models

After the classic serial/parallel dichotomy of visual search mechanisms has been increasingly doubted, we investigated what search mechanisms are used between the two poles termed "pop-out" and "strictly serial search" in an overt feature search paradigm. Since reaction time slopes do not contain sufficient information for this purpose, we developed a novel technique for analyzing reaction times. Individual reaction times are modeled as sums of the durations of successive search steps. Model parameters are task characteristics (similarity, number and arrangement of target and distractors) and processing characteristics of the participant (e.g., attention dwell and shift durations). In Experiment 1, several model variants were fitted numerically to empirical reaction times. The best fitting model suggested that more than one item can be processed in a single fixation, movement of attention is abrupt and not continuous, and even in pop out search, attention is often explicitly moved to the target. In Experiment 2, we measured the central model parameter, the so-called range of attention, more directly and thereby validated the model. The model provides an explanation for the strong variation in the slope of reaction time functions, which is not based on an explicit distinction between parallel and serial search processes.     

Exploring metacognitive accuracy in visual search

For decades, researchers have examined visual search. Much of this work has focused on the factors (e.g., movement, set size, luminance, distractor features and proximity) that influence search speed. However, no research has explored whether people are aware of the influence of these factors. For instance, increases in set size will typically slow down target detection; yet no research has measured participants' metacognitive awareness of this phenomenon. The present research explores this area by integrating a visual search task with a metacognitive monitoring paradigm. All of the explored factors influenced search latency. However, all of the factors except target presence influenced ratings. Saliency and suppression are discussed as two possible explanations for the results. Future directions for extending the theory and the practical benefits of this research are also outlined.     

Effects of speed and accuracy of exertion of force on the relationship between force output and fractionated reaction time

The present study was designed to investigate the effect of speed and accuracy of force exertion on the relationship between force output and fractionated reaction time. Subjects exerted their force (10% or 40% of maximum isometric contraction) on "accurate" and "fast" tasks as rapidly as possible at the light signal. On the "fast" task, premotor time for the 40% target was lengthened in comparison with that for the 10% target, and motor time was shortened with an increase of force output. On the "accurate" task, on the other hand, premotor time was independent of magnitude of force, and no relation between motor time and force output was found. These findings show that the relationship between force output and fractionated reaction time may be affected by the effort to exert force accurately.     

Fractal fluctuations in gaze speed visual search

Visual search involves a subtle coordination of visual memory and lower-order perceptual mechanisms. Specifically, the fluctuations in gaze may provide support for visual search above and beyond what may be attributed to memory. Prior research indicates that gaze during search exhibits fractal fluctuations, which allow for a wide sampling of the field of view. Fractal fluctuations constitute a case of fast diffusion that may provide an advantage in exploration. We present reanalyses of eye-tracking data collected by Stephen and Mirman (Cognition, 115, 154-165, 2010) for single-feature and conjunction search tasks. Fluctuations in gaze during these search tasks were indeed fractal. Furthermore, the degree of fractality predicted decreases in reaction time on a trial-by-trial basis. We propose that fractality may play a key role in explaining the efficacy of perceptual exploration.     

Effects of stimulus-response correspondence and verbal expectancy on choice reaction time.

The effects of S-R correspondence, verbal prediction, and stimulus discriminability were examined in a discrete, two-choice reaction-time task. Correctness of prediction and S-R correspondence were significant main effects. In addition, responses were significantly faster for correct predictions on noncorresponding trials than for incorrect predictions on corresponding trials. This latter finding indicates that an expectancy mechanism can partially offset the negative effect of spatial S-R noncorrespondence on absolute magnitude of choice reaction time.     

Effects of frontalis tension level on discrimination task accuracy and reaction time

The frontalis muscle is a focal point of many relaxation training programmes, so the effects of varying frontalis tension levels on concurrent task performance need consideration when recommending in situ muscle relaxation. Two experiments are reported; performance on a discrimination task was examined across high, moderate, and low induced frontalis tension. When length of exposure to the task stimuli was unlimited, accuracy of discrimination was affected by tension; when exposure was limited, reaction time was affected. In both experiments the high frontalis tension resulted in better performance than the other levels. Implications for the practice of in situ relaxation are considered.     

Effects of speed and accuracy strategy on choice step execution in response to the flanker interference task

The purpose of this study is to examine the effects of a speed or accuracy strategy on response interference control during choice step execution. Eighteen healthy young participants were instructed to execute forward stepping on the side indicated by a central arrow (←, left vs. →, right) under task instructions that either emphasized speed or accuracy of response in the neutral condition. In the flanker condition, they were additionally required to ignore the 2 flanking arrows on each side (→→→→→, congruent or →→←→→, incongruent). Errors in the direction of the initial weight transfer (APA errors) and the step execution times were measured from the vertical force data. APA error was increased in response to the flanker task and step execution time was shortened with a speed strategy compared to an accuracy strategy. Furthermore, in response to the visual interference of the flanker task, speed instructions in particular increased APA errors more than other instructions. It may be important to manipulate the level of the speed-accuracy trade-off to improve efficiency and safety. Further research is needed to explore the effects of advancing age and disability on choice step reaction in a speed or accuracy strategy.