The effects of different instructions for preparatory muscle tension on simple reaction time

The effects of preparatory weak muscular contraction (pre-tension) have been investigated in a number of previous studies using tasks with either simple or choice responses to measure the reaction time (RT). These studies suggested that optimal pre-tension performed prior to a motor response tends to shorten the RTs. Using a simple RT task in which participants performed a grip response to a visual stimulus, the present study compared the RTs between two pre-tension conditions (self-selection and constraint) to investigate the effects of different instructions for pre-tension. Under the self-selection condition, participants were asked to determine their optimal pre-tension levels while attempting to give responses as fast as possible. Under the constraint condition, the participants developed a pre-tension at a target force determined by the experimenter. The target force was set at the same level as the pre-tension level maintained under the self-selection. Despite the fact that the pre-tension level manipulated was the same for both conditions, the RTs were significantly shorter under self-selection than under constraint. Moreover, the present study showed a positive correlation coefficient between the proportion of shortening in RT and the variation of pre-tension level. This indicated a performance trade-off between the stability of pre-tension and RTs. The result suggests that shorter RTs that occur under self-selection are primarily mediated by mental factors, such as attention allocation, rather than by the effects of peripheral muscular preparation.     

Effects of electromyographic biofeedback on reaction time and movement time

The effects of electromyographic (EMG) biofeedback on reaction time (RT) and movement time (MT) were investigated utilizing 42 right-handed, male subjects from a university population. Subjects were randomly divided into three groups, a control group and two experimental groups. Both experimental groups were exposed to their EMG signals from their triceps brachii during the task, one experimental group received written information explaining the purpose of the EMG was to improve performance through biofeedback. Reaction times of the first block of 25 trials were significantly faster than those on the subsequent three blocks of trials for all groups. This provided evidence of learning. No other significant effects for reaction times were observed. Mean movement time for the EMG-only group was significantly slower than the means of either the Control group or EMG-Biofeedback group, with no difference between the latter two. The differences between experimental groups may have been related to alteration of strategy, anxiety, motivation.     

Effects of redundant auditory stimuli on reaction time

Auditory redundancy gains were assessed in two experiments in which a simple reaction time task was used. In each trial, an auditory stimulus was presented to the left ear, to the right ear, or simultaneously to both ears. The physical difference between auditory stimuli presented to the two ears was systematically increased across experiments. No redundancy gains were observed when the stimuli were identical pure tones or pure tones of different frequencies (Experiment 1). A clear redundancy gain and evidence of coactivation were obtained, however, when one stimulus was a pure tone and the other was white noise (Experiment 2). Experiment 3 employed a two-alternative forced choice localization task and provided evidence that dichotically presented pure tones of different frequencies are apparently integrated into a single percept, whereas a pure tone and white noise are not fused. The results extend previous findings of redundancy gains and coactivation with visual and bimodal stimuli to the auditory modality. Furthermore, at least within this modality, the results indicate that redundancy gains do not emerge when redundant stimuli are integrated into a single percept.     

Effects of uncertain warning signals on reaction time

Three experiments were conducted in an attempt to assess the effectiveness of a warning signal in reducing reaction time when (1) the signal to respond (danger signal) follows the warning signal with a probability less than 1.0, and (2) the interval between warning and danger signals (W-D interval) is variable. The required response was the depression of a foot pedal, as in automobile braking. It was determined that probabilistic warning information could be effective if observers made use of the W-D interval to prepare to make the response required by the danger signal. It was noted, however, that observers differed considerably in their tendency to do this. A model was proposed for describing different response strategies.     

Effects of moment of inertia on simple reaction time

Two experiments examined the effect of altering the moment of inertia within an anatomical unit on simple reaction time (SRT), premotor time (PMT), and motor time (MOT) during the initiation of a discrete rapid movement. In Experiment 1 (N = 14), moment of inertia of the forearm was increased with the addition of a weighted cuff fastened around the wrist. In Experiment 2 (N = 7), moment of inertia was altered by the addition of a weighted sleeve to the index finger prior to rapid extension of the digit. Results from both experiments were unequivocal. An increase in the moment of inertia resulted in a significant increase in SRT and MOT but had no significant effect on PMT. Within selected anatomical unites (forearm and index finger), an increase in the moment of inertia does not appear to require additional neuromotor programming time but does influence the overall duration of response initiation.     

Effects of time uncertainty and instructed muscle tension on fractionated reaction time

Abstract: An experiment was conducted to examine the effects of time uncertainty and instructed muscle tension on the reaction time of elbow flexion. Twenty-two right-handed subjects were asked to respond to an audio stimulus by flexing their right elbow under four conditions (2 time uncertainty × 2 instructed muscle tension). Electromyograms (EMGs) were recorded from the biceps and triceps on the subject's right side. Reaction time was divided into premotor time and motor time, based on the difference between the EMG and elbow flexion response. Analysis of reaction time showed that the effects of time uncertainty and instructed muscle tension were additive. Time uncertainty affected premotor time only, and instructed muscle tension affected motor time only. These results are discussed in terms of the assumption that premotor time is a reflection of the central nervous system and motor time is a reflection to the peripheral muscle system.     

Effects of fatigue and laterality on fractionated reaction time

Surface EMG enabled fractionation of a simple hand grip total reaction time into peripheral and central processing components (motor time and premotor time respectively). Changes in reaction time components were investigated in 12 female intercollegiate swimmers (bilateral athletes) and 12 female intercollegiate tennis players (unilateral athletes) following a 48% strength decrement induced by serial maximal voluntary isometric contractions (5 sec in duration). Despite significantly greater strength in the dominant arm than in the nondominant arm, there was no difference in fatigue effects between arms. Fatigue increased the premotor component of reaction time significantly, and indirectly the total reaction time, but the motor time remained essentially constant regardless of the type of previous athletic training. This indicated that fatigue impaired central nervous system or myoneural-junction operations rather than the intramuscular ability to initiate force.     

Effects of stimulus probability on reaction time in a number-naming task

Subjects were required to respond to the visual presentation of numerals by uttering syllables closely resembling the names of the numerals. Information in stimulus ensembles was varied by manipulating the number of alternative stimulus configurations that could appear, the relative frequencies of stimuli within an ensemble and the probability of a response being required. An increasing linear function was a good first approximation to the relation between reaction time and information transmission. Systematic deviations from this function were found and an attempt is made to explain them by introducing an intervening variable, “effective probability.”     

Effects of motivating operations on problem and academic behavior in classrooms

The current study examined the effects of motivating operations on problem behavior and academic engagement for 2 students with autism. Classroom sessions were preceded by periods in which the participants had access or no access to the items functionally related to their problem behavior. Results suggested that presession access may result in lower levels of problem behavior and higher levels of academic engagement during classroom instruction.     

Effects of attentional-focus instructions on movement kinematics

BackgroundRecent research has shown that internal (body-related) attention-focus instructions disrupt motor learning and performance, whereas paying attention to the environmental effects of movements (external focus) leads to better performance than an internal focus [see, for reviews, Wulf, G. (2007). Attentional focus and motor learning: a review of 10 years of research. E-Journal Bewegung und Training, 1, 4–14.; Wulf, G., &; Prinz, W. (2001). Directing attention to movement effects enhances learning: a review. Psychonomic Bulletin &; Review, 8, 648–660.]. However, Beilock's studies [Beilock, S. L., Bertenthal, B. I., McCoy, A. M., &; Carr, T. H. (2004). Haste does not always make waste: expertise, direction of attention, and speed versus accuracy in performing sensorimotor skills. Psychonomic Bulletin &; Review, 11, 373–379.] suggest that an internal focus is detrimental in experts but not in novices. Because detrimental effects of consciously attending to movements have generally been measured by performance scores such as accuracy scores or reaction times, it remains unclear how internal and external attentional-focus instructions influence movement kinematics when learning a new skill. To fill this gap, the present study investigated attentional-focus effects on a biomechanical level.MethodsA video of an expert juggler demonstrating a two-ball juggling task was presented to juggling novices. Experimental groups were given either body-related (internal group) or ball-related (external group) verbal instructions or no attention-guiding instructions (control group). In the retention phase without attention-guiding instructions, the body-movement and ball-flight aspects of performance focused on in the verbal instruction were subjected to biomechanical analyses.Results and ConclusionsJuggling performance improved equally in all three groups. However, internally vs. externally instructed acquisition phases had differential effects on the kinematics of the upper body as well as ball trajectories when performing the juggling task. Remarkably, ball trajectories in the control group who received no specific attentional cueing were similar to those in the externally instructed group. This suggests that task-relevant information is picked up independently of instructions, and that external instructions provide redundant information. Internal instructions for object-related tasks, however, may confront novice learners with the need to process additional information. As a result, task difficulty might be unnecessarily enhanced in an observational learning setting.     

Effects of stimulus frequency and reinforcement variables on reaction time

Pigeons pecked at one of two black forms, “+” or “O,” either of which could appear alone on a white computer monitor screen. In baseline series of sessions, each form appeared equally often, and two pecks at it produced food reinforcement on 10% of trials. Test series varied the relative probability or duration of reinforcement or frequency of appearance of the targets. Peck reaction times, measured from target onset to the first peck, were found to vary as a function of reinforcement probability but not as a function of relative target frequency or of reinforcement duration. Reaction times to the two targets remained approximately equal as long as the probability of reinforcement, per trial, was equal for the targets, even if the relative frequency of the targets differed by as much as 19 to 1. The results address issues raised in visual search experiments and indicate that attentional priming is unimportant when targets are easy to detect. The results also suggest that equalizing reinforcement probability per trial for all targets removes differential reinforcement as an important variable. That reaction time was sensitive to the probability but not the duration of reinforcement raises interesting questions about the processes reflected in reaction time compared with rate as a response measure.