Cardiac cycle phase and movement and reaction times.

The EKG was recorded while Ss differentially responded to auditory or visual stimuli in a reaction time task. The EKG record was analyzed by dividing each R-R interval encompassing a stimulus presentation into 9 equal phases. Reaction times were determined as a function of the phase encompassing stimulus onset while movement times were determined for the phase in which the response was initiated. Only reaction time significantly varied with cardiac cycle, with reactions during the second phase being slower than later phases.     

Structural complexity of motor patterns: A study on reaction times and movement times of handwritten letters

This study investigates the effects of psychomotor complexity on latencies for beginning to write single letters and numerals, and on times taken to complete the first strokes of letters and numerals. An experiment measured simple and choice reaction times for writing homogeneous graphemes (i.e., letters or numerals made up of similar strokes) and for writing heterogeneous graphemes (i.e., characters made up of dissimilar strokes). It was assumed that the motor programme for writing a letter is retrieved from long-term memory and briefly held, until it is used, in a short-term buffer store. The experiment examined the hypothesis that it is more difficult to read out homogeneous than heterogeneous stroke-structures from this store. For three out of four allographic grapheme pairs, homogeneous graphemes required longer initiation times or longer movement times for completion of the first stroke than did heterogeneous graphemes. These results are discussed in relation to recent findings on motor programming based on the use of reaction-time paradigms.     

Spatial attention and reaction times during smooth pursuit eye movement

To examine the spatial shift of attention during smooth pursuit, we measured reaction times (RTs) to a visual target that appeared during pursuit. Participants pursued a moving row of circular frames and responded to a target presented within one of the frames. The results showed large RT differences between stimulus velocities up to 5o/s and 10o/s or above. RTs were faster for a target appearing in the pursuit direction than for one in the opposite direction. When an auditory precue was presented, the RTs during pursuit at 10o/s were faster with increases in the stimulus onset asynchrony (SOA) between the cue and the target. Furthermore, RTs were faster in the cued than in the uncued direction. These results not only support the idea that RTs during pursuit reflect the operation of attention, but also suggest that attention during pursuit can be shifted by the abrupt onset of a target stimulus and/or by prior information regarding the onset of a target stimulus.     

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 directional auditory and visual warnings at intersections on reaction times and speed reduction times

Intersection collision warning systems (ICWSs) have an important impact on driving safety because making the potential collision at intersection predictable, allow reducing the probability and severity of accidents. Among the several types of alarms to alert the driver of an imminent collision, those most used concerning the auditory and the visual stimulus. However, it is unclear whether is more effective an audio or a visual warning. In addition, no study compared the effects on drivers’ behavior induced by an acoustic and a visual directional warning. The main objective of the present study was to assess, in response to a potential conflict event at the intersections, the effects of directional auditory and visual warnings on driving performance.A driving simulator experiment was carried out to collect drivers’ behavior in response to a vehicle that failed to stop at the intersection. The parameters reaction time and speed reduction time were used for the evaluation of the effects on driving performance. These duration variables were modeled following the survival analysis, by the use of the accelerated failure time duration model with a Weibull distribution.Results showed that when the directional warning system (auditory or visual) was present, the drivers were able to detect earlier the violator vehicle. This effect led to a more comfortable braking maneuver and, thus, less possibilities of an unexpected maneuver for the following vehicle, avoiding the car – following collisions. The effectiveness of ICWSs was more evident for the directional auditory speech message; for this condition, in fact, the lower reaction time and the longer speed reduction time were obtained.The outcomes of the present study provide useful suggestions about the most effective collision warning systems that the automotive industry should develop and equip on vehicles.     

Effects of intrahemispheric interference on reaction times to lateral stimuli

Earlier work (Green, 1977) indicated that response by a given hand was slower when stimuli occurred in the visual half field ipsilateral to the body side of hand origin. It was hypothesized that this was due to interference between processing demands originating within the same hemisphere. The present experiments provide evidence regarding the relationship between such interference and the magnitude and type of processing demands. The eight experiments indicate that intrahemispheric interference affects a variety of tasks, including letter shape, letter name, or face matching. The results indicate that reduction in response processing demands reduces the interference. Evidence of interference appeared with a more demanding choice response, but not with a simpler go-no-go response. Manipulations hypothesized to reduce initial, perceptual stimulus processing demands did not reduce the magnitude of interference, possibly because the level of more central stimulus processing demands was still sufficient to interfere with response processing. Interference tended to be minimal on right-hand, match trials, which are hypothesized to involve reduced response processing and reduced central stimulus processing demands. Further investigation of the effects of stimulus processing demands is required.     

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.     

Effects of cocaine on simple reaction times and sensory thresholds in baboons.

The effects of chronic, daily administration of cocaine on auditory and visual reaction times and thresholds were studied in baboons. Single intramuscular injections of cocaine hydrochloride (0.1 to 5.6 mg/kg) were given once daily for periods of 10 to 25 days, and were followed immediately by psychophysical tests designed to assess cocaine's effects on simple reaction times as on auditory and visual threshold functions. Consistent reductions in reaction times were frequently observed over the cocaine dose range of 0.32 to 1.0 mg/kg; at higher doses, either decreases or increases in reaction times were observed, depending upon the animal. Lowered reaction times generally occurred immediately following the 1st day's cocaine injection, and continued through all subsequent days during the dose administration period, suggesting little development of tolerance or sensitivity to these reaction-time effects. Reaction-time decreases showed a U-shaped dose-effect function. The greatest decreases in reaction times occurred from 0.32 to 1.0 mg/kg, and produced an average reaction-time decrease of 10 to 12%. Concurrently measured auditory and visual thresholds showed no systematic changes as a function of cocaine dose. Pausing was observed during performance of the psychophysical tasks, with the length of total session pause times being directly related to cocaine dose.     

Effects of concurrent arithmetical and syntactic complexity on self-paced reaction times and eye fixations

Two dual-task experiments (replications of Experiments 1 and 2 in Fedorenko, Gibson, & Rohde, Journal of Memory and Language, 56, 246–269 2007) were conducted to determine whether syntactic and arithmetical operations share working memory resources. Subjects read object- or subject-extracted relative clause sentences phrase by phrase in a self-paced task while simultaneously adding or subtracting numbers. Experiment 2 measured eye fixations as well as self-paced reaction times. In both experiments, there were main effects of syntax and of mathematical operation on self-paced reading times, but no interaction of the two. In the Experiment 2 eye-tracking results, there were main effects of syntax on first-pass reading time and total reading time and an interaction between syntax and math in total reading time on the noun phrase within the relative clause. The findings point to differences in the ways individuals process sentences under these dual-task conditions, as compared with viewing sentences during “normal” reading conditions, and do not support the view that arithmetical and syntactic integration operations share a working memory system.     

Effects of variation in the warning signal on reaction times of severe subnormals

Reaction times of normal and subnormal subjects were compared, when a warning stimulus varied in modality as well as in its temporal relation to the RT signal. When the warning stimulus was in a different modality from the RT signal, reaction times were shorter than when both were in the same modality. Mongols, in contrast to the other subjects, responded relatively faster to light than to sound.

The effect of varying the time interval between warning and signal was linearly related to response speed. The results are discussed in respect to the comparative alerting effects of temporal relations between stimuli and their different modalities.     

Learning and locomotor reaction times

To help measure contributions by learning to latencies of complex locomotor responses, an operant stimulus-response unit was constructed and timed during human treadmill walking. A light flash served as discriminative stimulus (Sd) to produce electromyographic activity (EMG) of predefined filtered amplitude and duration by the leg muscle, rectus femoris (RF). A computer scored every EMG as successful or not (indicated by a high or low tone, respectively). The EMG burst also had to occur within successively shorter performance durations (PDUR), to a criterion of 80% successful responses. Among six adults, the shortest estimated reaction time was 110 msec. Relative strength of the operant unit was measured in relation to RF activity that occured in non-light step cycles or that was a by-product of the reinforcement regimen. It was proposed that operant latencies, after being minimized by specific conditioning regimens, can permit accurate timing of intervening neural events.     

Macroscopic thermodynamics of reaction times

I present a new interpretation of reaction time (RT) data from behavioural experiments. From a physical perspective, the entropy of the RT distribution–the temporal entropy–provides a model-free estimate of the amount of processing performed by the cognitive system. This new measure shifts the focus from the conventional interpretation of RTs being either long or short, into their distribution being more or less complex in terms of entropy. I introduce the formulation of the theory, followed by an empirical test using a large database of human RTs in lexical processing tasks. Using the measure, I obtain estimates of the processing loads to individual stimuli (i.e., words), as well as estimates for the overall rate at which the system processes information in these tasks. The relation between the temporal entropy and the RTs can be captured by a simple linear equation. I argue that this equation constitutes the equivalent of a ‘phase diagram’ of a task, providing indications about the different mechanisms that are at play in it, and locating critical points signalling the transitions between these different mechanisms. The results suggest an adaptive system that adjusts its operational processing speed to the demands of each individual stimulus. This finding is in contradiction with a generalization of Hick’s Law positing a relatively constant processing speed within an experimental context.     

Subjective expectancy and choice reaction times

Previous findings suggested that selective response times might be affected both by the inter-stimulus interval and by the probability of occurrence of the stimulus for reaction. These two factors have been tested independently and have been found to influence reaction times in a fashion that an expectancy hypothesis would predict.     

Mediators of perceptions of stress among community-based elders

Research focusing on the relationship between the frequency of stressful life events and perceptions of stress among the aged has increased considerably over the past few decades. The present research focused on expanding the simple life-events/stress-perceptions paradigm by including several other variables that have previously been assumed to be associated with an increase in perceptions of stress among elderly persons. More specifically, the present investigation concerned evaluation of mediating effects of levels of social support, problem-solving, and frequency of daily hassles on the perceptions of stress by elderly individuals. A prospective design evaluated over a 24-mo. period was used to assess the mediating effects. A conceptual model of mediating effects was tested using path analysis statistical techniques on data from a sample of 80 community-based elderly volunteers. The postulated model accounted for 53% of the variance associated with the prediction of perceptions of stress among the elderly subjects. Implications for current theory and research in the study of mediating variables in the stress symptomatology of older adults are discussed.     

Warned reaction times of sociopaths

A warned reaction time (RT) task was employed with eight male sociopaths and eight normal male Ss. A warning light appeared at a variable interval preceding a light to which the S responded with a key press. All Ss received both a regular and an irregular series with warning intervals of 1, 2, 4, 8, and 16 sec. In the regular series, blocks of intervals were presented in an ascending order. In the irregular series each interval followed every other interval equally often. Sociopaths obtained reliably slower RTs than did control Ss, showing a constant decrement across all intervals in the two kinds of series.     

Visual and auditory choice reaction times

Choice reaction times are measured for three values of a priori signal probability with three well-practiced observers. Two sets of data are taken with the only difference being the modality of the reaction signal. In one set of conditions it is auditory, in the other, visual. The auditory reaction times are faster than the visual and in addition several other differences are noted. The latency of the errors and correct responses are nearly equal for the auditory data. Error latencies are nearly 30% faster for the visual data. Non-stationary effects, autocorrelation between successive latencies and non-homogeneous distribution of errors, are clearly evident in the visual data, but are small or non-existent in the auditory data. The data are compared with several models of the choice reaction time process but none of the models is completely adequate.     

A meta-analysis of subjective well-being interventions among elders

This meta-analysis demonstrated that interventions have a significant (p less than .05) immediate posttreatment influence on elders' subjective well-being but that their beneficial effect dissipates within 1 month. For 28 effect sizes derived from immediate posttreatment occasions (delay = 0 days), the median value was 0.67. Immediate posttreatment effect sizes for control enhancement (M = 1.12), psychoeducational (M = 0.70), and social activity (M = 0.66) treatments were significantly (p less than .05) above zero and not significantly different from each other. In contrast, for 17 effect sizes derived from delayed posttest occasions (delay greater than 0 days), the median value was 0.07. For effect sizes extracted from studies with both an immediate and a delayed posttest, the mean decrease over a 30-day period was 1.02.     

Oral/manual motor reaction times and delayed auditory feedback disturbances among normally speaking females

Research has indicated that stuttering and nonstuttering groups can be differentiated on the basis of certain motor reaction time variables. This study evaluated the manual and oral reaction times to a 1000 Hz stimulus tone in 39 normally speaking college females. Speech disfluencies of the subjects (Ss) were identified by a four-judge panel and correlated with reaction time scores. Although no significant correlations were obtained, it was observed that Ss with faster oral and manual reaction times tended to have more disfluencies under delayed auditory feedback.