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 mood states and anxiety as induced by the video-recorded stroop color-word interference test in simple response time tasks on reaction time and movement time

Mood states and anxiety might alter performance in complex tasks whereas in more simple tasks such as stimulus-response, high anxiety could provoke bias in mechanisms of attention leading to better performances. We investigated the effects of anxiety, tension, and fatigue induced by the video-recorded Stroop Color-Word Interference Test on either reaction or movement time. 61 subjects performed a visual and an auditory response-time test in Control and Anxiogenic conditions during which heart rate was measured. Tension and anxiety states were assessed using self-evaluation. Analysis showed auditory response time was improved for both reaction and movement times in the Anxiogenic condition. These data suggest that the increased attention underlying anxiety and mood responses could have favored auditory response time by leading subjects to process stimuli more actively. In addition, state-anxiety and tension could have influenced muscular tension, enhancing the movement time in the auditory task.     

Programming of time-to-peak force for brief isometric force pulses: Effects on reaction time

According to the parallel force unit model (PFUM) the programming of an isometric force pulse requires the specification of the number of force units and force unit duration. The programming of a force pulse with minimal time-to-peak force is an exception, however, as force unit duration is limited by the minimal possible value, which should be easier to adjust than larger force unit durations. Therefore, the duration of the programming process should be shorter for these force pulses and hence should result in shorter reaction time (RT). Four experiments assessed this prediction using a response precueing procedure. In each experiment the participants produced isometric flexions with their left or right index finger, and time-to-peak force was manipulated within a block. The results are consistent with the predictions of PFUM. The results, however, are at variance with alternative accounts which assume that RT depends primarily on response duration or rate of force production.     

Probability effects in choice reaction time tasks

This paper contains a short review of the main results that were obtained by the author in a series of experiments that constituted a study of the effects of signal probability on choice reaction time. The effects of stimulus probability are shown to be influenced by the following variables: (1) differences in the method of varying stimulus probability, (2) differences in task complexity, (3) differences in S-R code, and (4) differences in Ss’ motivation. The data that are considered here are the overall mean RT for particular signals and the mean RT for sequential repetitions. Two questions, related to the psychological “nature” of the probability effects in choice RT are discussed: (1) The question of the relationship between the relative frequency and the number of alternatives as two different ways of determining the probability effect in choice RT; and (2) the question of identifying the main determinants of the trial-to-trial variability of RT in such experiments.

     

Routes to action in reaction time tasks

Summary Two-choice tactile RTs are no faster than 8-choice tasks, implying the existence of a direct route. However, simple tactile RTs are much faster than choice tactile RTs (Leonard, 1959). In Experiment I we show that this is not due to subjects anticipating the stimulus in simple tactile RT tasks. Increasing probability of stimulus occurrence at a particular time led to equally decreased tactile RTs for simple and choice tasks.We suggest that an alternative route is available for simple RTs which is faster than the direct route available for choice tactile RTs. This route is faster because (a) the response can be specified in advance, and (b) the stimulus does not need to be identified. The subject needs merely to register that it has occurred. In Experiment II we show that simple RTs to a visual stimulus are decreased by a simultaneous uninformative tactile stimulus even when this is to the wrong finger. This confirms that exact stimulus identification is not necessary in the fast route. In Experiment III we show that a secondary task slows down simple tactile RTs to the same level as choice tactile RTs while the latter are hardly affected. This suggests that focussed attention is not needed for the direct route, but it is needed for the fast route. We propose that a useful distinction can be made between action largely controlled by external stimuli (the direct route) and action largely controlled by internal intentions of will (the fast route).     

Hemispheric competition in left-handers on bimanual reaction time tasks

The authors examined possible differences in left- and right-handers on bimanual reaction times to centralized visual stimuli. Eighty participants (n = 40 in each group of left- and right-handers) were tested on unimanual and bimanual reaction time (RT) tasks. Consistently across the 2 groups, the dominant-hand RT was faster, on average, than the nondominant-hand RT, and unimanual RTs were faster than bimanual RTs. However, RT differences between hands revealed a higher percentage of dominant-hand-led trials in right-handers than in left-handers, despite similar absolute RT differences in the 2 groups. On the basis of those findings, the authors conclude that hand dominance does not generally determine which hand leads in a bimanual task and that left-handers have stronger between-hemisphere competition than right-handers do.     

Effects of average movement velocity on reaction time and spatiotemporal accuracy in single-aiming and rapid-timing movement tasks

The effects of instructed movement speed were investigated in two experiments. First, rapid-timing and single-aiming movement tasks were compared. Unlike rapid timing, single aiming implies spatial accuracy. The aim of the first experiment was twofold: (a) to examine whether the requirement of accurate placement termination in single aiming affects the negative relationship between instructed average velocity and reaction time found in rapid timing, and (b) to test the speed-accuracy relationships predicted by the symmetric impulse variability model of these movement tasks. For this purpose, four average velocities (5, 24, 75, and 140 cm/s) were investigated in both types of movement tasks in a two-choice reaction task. The effects of average velocity on reaction time were similar in both single-aiming and rapid-timing tasks, and the predicted linear relationship between instructed average velocity and spatial accuracy was not found. The results suggest that the movement control mode, that is, open loop or closed loop, interferes with effects of instructed average velocity. The movement control mode explanation was confirmed in the second experiment with respect to the effect of paired velocities on reaction time. It is argued that the type of movement control mode must be considered in the interpretation of effects of instructed average velocity on reaction time and spatiotemporal measures.     

Stimulus-specific sequence representation in serial reaction time tasks

Some recent evidence has favoured purely response-based implicit representation of sequences in serial reaction time tasks. Three experiments were conducted using serial reaction time tasks featuring four spatial stimuli mapped in categories to two responses. Deviant items from the expected sequence that required the expected response resulted in increased response latencies. The findings demonstrated a stimulus-specific form of representation that operates in the serial reaction time task. No evidence was found to suggest that the stimulus-specific learning was contingent on explicit knowledge of the sequence. Such stimulus-based learning would be congruent with a shortcut within an information-processing framework and, combined with other research findings, suggests that there are multiple loci for learning effects.     

Sequential effects in auditory choice reaction time tasks

This paper concerns sequential effects in choice reaction time tasks. Performance in two interleaved auditory tasks was examined, and two general types of sequential effects were revealed. First, a response repetition effect occurred: Subjects were facilitated in responding when both the stimulus and the response were immediately repeated. Generally, it appeared that subjects were operating according to the bypass rule—that is, repeat the response if the stimulus or some aspect thereof is repeated from the preceding trial; otherwise, change the response. In addition, the experiment also revealed a second type of sequential effect, known as a task-switching effect. Subjects were overall slower to respond when the task changed between adjacent trials than when there was no task change. A final result was that subjects were markedly impaired when the stimulus changed but the same response had to be repeated. This finding has been reported elsewhere when purely visual tasks have been used. Hence, it seems that particular difficulties arise, in such sequential testing situations, when type-distinct stimuli are grouped into the same response categories.     

Effects of initial limb position on the accuracy, reaction time and electromyographic patterns of rapid movements

An experiment was performed to determine the effects of initial limb condition on final accuracy of rapid, elbow flexion movements in the horizontal plane. Electromyographic (EMG) recordings were also taken from an agonist (biceps) and antagonist (triceps) muscle by means of bipolar surface electrodes. In the experiment the subject's forearm was passively oscillated by means of an electric motor, and when an auditory buzzer sounded, the subject was required to react as quickly as possible and rapidly move to the previously learned target angle. Thus, movements could be initiated from either static or moving starting positions. The results indicated that general accuracy was not greatly affected by these manipulations, however, constant error and pre-motor reaction time suggested that subjects may have been utilizing initial limb condition information contrary to a mass-spring view. EMG data showed that the timing characteristics of the agonist and antagonist muscles were modulated, depending on the type of movement produced, supporting an impulse-timing model (Wallace 1981).     

Covert signs of expectancy in serial reaction time tasks revealed by event-related potentials

Choice reaction time is strongly determined by the sequence of preceding stimuli. With long response-stimulus intervals (RSIs), a cost-benefit pattern is observed, which has been related to expectancy, whereas with short RSIs a benefit-only pattern emerges, possibly because of automatic facilitation. In the present study, event-related potentials were recorded while subjects performed serial choice responses to visual and auditory stimuli at long and short RSIs. As expected, reaction times displayed cost-benefit and benefit-only patterns at long and short RSIs, respectively. In contrast, sequential effects in event-related potential amplitudes displayed a cost-benefit pattern, unaffected by the RSI. The results demonstrate that an expectancy-like mechanism is always active in serial tasks but appears to influence performance only when the RSI is long.     

The independence of reaction and movement time in programmed movements

The issues of controlled vs automatic processing, and programmed vs preprogrammed movements deal with two problems, whether subjects can control their performance, and whether RT is related to task difficulty. The subjects' control over the relationship of RT and movement was examined. Two experiments are reported in which the relationship between RT and MT is investigated using instructional set and speed-accuracy tradeoff techniques. The two issues considered were: (1) whether subjects could separate their RT and MT in a top-down approach; (2) whether RT could be independent of MT and accuracy. The two experiments separated RT and MT using instructional set and feedback bands in a simple horizontal aiming movement. A relationship was found between RT and movement accuracy. The implications for preprogramming and programming are briefly discussed.     

Effect of loudness on reaction time and response force in different motor tasks

Van der Molen and Keuss, in 1979 and 1981, showed that paradoxically long reaction times occur with extremely strong auditory stimuli when the task is difficult, e.g., choice-by-location or Simon paradigm. It was argued that this paradoxical behavior of RT is due to active inhibition of an arousal-dependent bypassing mechanism to prevent false responses. As the peak force, i.e., maximal force exerted by participants on a response key, is considered to be related to immediate arousal, we predicted that for extremely loud stimuli and for difficult tasks, lengthening of RT should be associated with reduction of peak force. Moreover, these effects should be enhanced when emphasis is on accuracy rather than speed. Although the relation between RT and intensity depended on task difficulty, no increase in RT was found for the loudest tones. Moreover, peak force increased monotonically with loudness, showing no tendency to be suppressed for loudest tones and difficult tasks.     

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.     

Locus of the intensity effect in simple reaction time tasks

Evidence is still inconclusive regarding the locus of the stimulus intensity effect on information processing in reaction tasks. Miller, Ulrich, and Rinkenauer (1999) addressed this question by assessing the intensity effect on stimulus- and response-locked lateralized readiness potentials (LRPs) as indices of the sensory and motor parts of reaction time (RT). In the case of visual stimuli, they observed that application of brighter stimuli resulted in a shortening of RT and stimulus-locked LRP (S-LRP), but not of response-locked LRP (R-LRP). The results for auditory stimuli, however, were unclear. In spite of a clear RT reduction due to increased loudness, neither S-LRP nor R-LRP onset was affected. A reason for this failure might have been a relatively small range of intensity variation and the type of task. To check for this possibility, we performed three experiments in which broader ranges of stimulus intensities and simple, rather than choice, response tasks were used. Although the intensity effect on the R-LRP was negligible, S-LRP followed RT changes, irrespective of stimulus modality. These findings support the conclusion that stimulus intensity exerts its effect before the start of motoric processes. Finally, S-LRP and R-LRP findings are discussed within a broader information-processing perspective to check the validity of the claim that S-LRP and R-LRP can, indeed, be considered as pure estimates of the duration of sensory and motor processes.     

The relationship between reaction time and intensity in discrete auditory tasks

The effect of signal intensity upon reaction time (RT) was studied in three auditory RT tasks in which the signal was a tone of high or low frequency. Experiment I showed the well-known negative gradient with intensity of simple RT when the subject was instructed to ignore the frequency and give the same response to both tones. But when the subject had to discriminate the frequency in a choice RT task, the RT/intensity relationship appeared to be U-shaped. Experiment II showed that when the subject was required to make a response to one signal but withhold it for the other, a task which requires discrimination of the frequency of the tone but removes the necessity to choose between overt responses, no increase in RT at high intensities was obtained. The results indicate that it is the response choice stage rather than the stimulus encoding stage which is retarded at higher energy levels. Experiment I also demonstrated that visual and auditory leading signals have similar facilitating effects without affecting the RT/intensity relationships.     

Attention and hemispheric differences in reaction time during simultaneous audio-visual tasks

The effect of different types of competing auditory tasks on laterality differences in visual perception was investigated. Right-handed subjects were presented with digits which occurred randomly in the left or right visual fields. They responded vocally to previously specified digits in a go, no-go reaction time situation. In the absence of any competing auditory task, digits presented in the right visual field were processed more quickly. This visual field difference in reaction time was in the same direction while subjects performed a secondary musical task. However, when a secondary verbal task had to be performed, digits in the left visual field received faster responses. The results support the view that the right hemisphere is capable of some language functions, and that hemispheric differences in performance have at their basis a quantitative asymmetry, which can be reversed even in normal subjects by overloading their limited capacity.     

Experience-dependent effects in unimanual and bimanual reaction time tasks in musicians

Engaging in musical training has been shown to result in long-term cognitive benefits. The authors examined whether basic cognitive-motor processes differ in people with extensive musical training and in nonmusicians. Musicians (n = 20) and nonmusicians (n = 20) performed a simple reaction time (RT) task under unimanual and bimanual conditions. Musicians' RTs were faster overall than were those of nonmusicians, and those who began their musical training at an earlier age (around age 7-8 years, on average) exhibited a larger bimanual cost than did those who began later (around 12 years, on average). The authors conclude that experience-dependent changes associated with musical training can result in greater efficacy of interhemispheric connections if those changes occur during certain critical periods of brain development.