Post-error adjustments occur in both reaching and grasping.

Post-error slowing (PES), the tendency to slow down a behavioral response after a previous error, has typically been investigated during simple cognitive tasks using response time as a measure of PES magnitude. More recently, PES was investigated during a single reach-to-grasp task to determine where post-error adjustments are employed in a more ecological setting. Kinematic analyses in the previous study detected PES during pre-movement planning and within the grasping component of movement execution. In the current study (N = 22), we increased the cognitive demands of a reach-to-grasp task by adding a choice between target and distractor locations to further explore PES, and other post-error adjustments, under different task conditions. We observed a significant main effect of task condition on overall reaction time (RT); however, it did not significantly impact PES or other post-error adjustments. Nonetheless, the results of this study suggest post-error adjustment is a flexible process that can be observed during pre-movement planning and within the onset and magnitude of the reaching component, as well as in the magnitudes of the grasping component. Considering the sum of the results in the context of existing literature, we conclude that the findings add support to a functional account of error reactivity, such that post-error adjustments are implemented intentionally to improve performance.

Sex differences in visuospatial cognition- a female advantage in jigsaw puzzle solving.

Mentally visualizing objects, understanding relationships between two- or three- dimensional objects, and manipulating objects in space are some examples of visuospatial abilities. Numerous studies have shown that male participants outperform female participants in visuospatial tasks, particularly in mental rotation. One exception is solving jigsaw puzzles. Performance by seven- to eight-year-old girls was found to be superior to that of boys of the same age (Kocijan et al. 2017). No study, however, has confirmed this finding in an adult population, where sex differences are often detectable. Seventy-nine young adult participants were given four different jigsaw puzzles and the Shepard and Metzler mental rotation test (MRT) with two main goals: First, to investigate possible sex differences in jigsaw puzzle solving, and second, to explore a potential relationship between mental rotation and jigsaw puzzle solving. We hypothesized that female participants would outperform males in the jigsaw puzzles but males would outperform females in the MRT. The findings confirmed this hypothesis. Notably, the male performance in jigsaw puzzle solving was attributed to their sex and mediated by their higher MRT scores. These results yielded two key insights. First, they indicate a dissociation between these two visuospatial abilities, jigsaw puzzle solving and mental rotation; and second, female and male participants capitalize on their distinct cognitive strengths when solving visuospatial tasks.

Short-term Effects of Static Stretching on Hamstring Passive Stiffness in Young and Older Women.

OBJECTIVES: The objectives of this study were to assess the acute effects of static stretching on hamstring passive stiffness in young and older women. A secondary objective was to compare hamstring muscle size and quality measurements (cross-sectional area and echo intensity) between the two groups and to determine if these characteristics are related to passive stiffness at baseline. METHODS: Fifteen young (23±4 years) and 15 older (73±5 years) women underwent two randomized conditions that included a control treatment and an experimental treatment of four, 15-s static stretches of the hamstrings. Passive stiffness was calculated before (pre-test) and after (post-test) each treatment using a passive knee extension test. Ultrasound imaging was used to measure hamstring muscle cross-sectional area and echo intensity. RESULTS: Passive stiffness collapsed across group decreased from pre- to post-test for the stretching treatment (P=0.001) but not for the control (P=0.467). The older women had lower cross-sectional area (P=0.033) and greater baseline (pre-test) passive stiffness (P=0.042-0.049) and echo intensity (P=0.022) than the young women. Moreover, baseline passive stiffness was significantly related to echo intensity (r=0.430, P=0.018) but not cross-sectional area (r=-0.014, P=0.943). CONCLUSION: An acute bout of static stretching decreased passive stiffness in both young and older women.

Tradeoffs of estimating reaction time with absolute and relative thresholds.

Measuring the duration of cognitive processing with reaction time is fundamental to several subfields of psychology. Many methods exist for estimating movement initiation when measuring reaction time, but there is an incomplete understanding of their relative performance. The purpose of the present study was to identify and compare the tradeoffs of 19 estimates of movement initiation across two experiments. We focused our investigation on estimating movement initiation on each trial with filtered kinematic and kinetic data. Nine of the estimates involved absolute thresholds (e.g., acceleration 1000 back to 200 mm/s2, micro push-button switch), and the remaining ten estimates used relative thresholds (e.g., force extrapolation, 5% of maximum velocity). The criteria were the duration of reaction time, immunity to the movement amplitude, responsiveness to visual feedback during movement execution, reliability, and the number of manually corrected trials (efficacy). The three best overall estimates, in descending order, were yank extrapolation, force extrapolation, and acceleration 1000 to 200 mm/s2. The sensitive micro push-button switch, which was the simplest estimate, had a decent overall score, but it was a late estimate of movement initiation. The relative thresholds based on kinematics had the six worst overall scores. An issue with the relative kinematic thresholds was that they were biased by the movement amplitude. In summary, we recommend measuring reaction time on each trial with one of the three best overall estimates of movement initiation. Future research should continue to refine existing estimates while also exploring new ones.

Differential effects of aging on spatial abilities.

Visuospatial functions are particularly vulnerable to the aging process. Decline of these processes can seriously affect an individual's functional independence and quality of life. Effectively assessing the spatial abilities of older adults is, therefore, crucial for identifying strategies to maintain cognitive functioning. The purpose of the present study was to use ecological tasks more comparable to activities of daily living to assess spatial ability in older adults. Three hands-on tasks (a visual search task, a low- and a high-mental rotation demand tasks) and a version of the well-known paper-based mental rotation of figures test (Shepard and Metzler, Science 171(3972):701-703, 1971) were given to 60-79-year-old female and male participants. The hands-on tasks required participants to locate, manipulate, and arrange real objects (i.e., toy bricks) in space. Age had a negative impact on visual search but not on mental rotation ability. Male participants outperformed females in the mental rotation tasks, but a trend for the opposite (better performance by females) was found for the visual search task. The results suggest that spatial abilities are not a monolithic construct and that sub-categories of this construct are affected by age and by sex differently. While visual search function is susceptible to decline during old age, mental rotation ability is not. In addition, unlike the paper-based test, the hands-on tasks were found to be age-appropriate with a feasible level of difficulty for all participants. The hands-on tasks may be more appealing as a tool to evaluate, maintain, and/or enhance spatial function in older adults.

The Acute Effects of Fast-Paced Walking on Isometric Peak Torque and Rate of Torque Development in Regularly Exercising and Inactive Older Women.

This study aimed to examine the acute effects of fast-paced walking on isometric peak torque and rate of torque development (RTD) in regular exercising and inactive older women. Ten regular exercising (67 ± 4 years) and 10 inactive (68 ± 4 years) older women performed three isometric knee extension contractions before and after a control condition (quiet resting) and an experimental condition of fast-paced walking for 6 min. Peak torque and early (RTD100), late (RTD200), and maximum (peak RTD) RTD measurements were obtained from each contraction. Results showed no significant changes in peak torque, peak RTD, or RTD200 after walking for either group (p > .050). A significant decrease in RTD100 was observed after walking for the inactive group (p = .005) but not for the regular exercisers (p = .909). These findings highlight the importance of physical activity and suggest that a task as simple as walking may impair the rapid strength capacities of inactive older women.

Low-Pass Filter Effects on Metrics of Countermovement Vertical Jump Performance.

ABSTRACT: Harry, JR, Blinch, J, Barker, LA, Krzyszkowski, J, and Chowning, L. Low-pass filter effects on metrics of countermovement vertical jump performance. J Strength Cond Res 36(5): 1459-1467, 2022-Countermovement vertical jump (CMVJ) studies using ground reaction force (GRF) data analyze either unfiltered (i.e., raw) or filtered data while providing little-to-no justification for the selected filtering process. Inappropriate filter choices can lead to inaccurate study results and erroneous interpretations. We examined the effects of not filtering GRF data in comparison with filtering data with various objectively and subjectively selected cutoff frequencies. Twenty-one collegiate male basketball players completed 3 maximal-effort CMVJ trials while GRF data were obtained from 2 force platforms. Countermovement vertical jump performance, explosiveness, power output, and neuromuscular function variables were compared among the following methods using one-way repeated-measures analyses of variance (α = 0.05): no filtering (raw data), a standard 50-Hz cutoff (50 Hz), a visually determined cutoff frequency describing the frequency band containing the majority of the summed (visual inspection 1) or not-summed (visual inspection 2) GRF signal's frequency content, filtering the summed (99% signal power 1) or not-summed (99% signal power 2) GRF using a cutoff frequency retaining 99% of the signal power. The raw data method produced significantly shorter concentric phase times and significantly greater center of mass flight heights (∼3%), modified reactive strength indices (RSIMOD; ∼4%), power outputs (∼6%), and push-off distances (∼4%) than 99% signal power 1 and 2 (p < 0.05). Discrete GRF and phase-specific yank magnitudes were not different among methods (p ≥ 0.05). Importantly, no differences were detected between the raw data and 50 Hz methods for any variable (p > 0.05). Low-pass filtering is not necessary when analyzing GRF data from the CMVJ. However, a low-pass filter with a 50-Hz cutoff can remove noise without altering results when compared with raw data. Explicit methodological descriptions of filtering processes should always be provided to improve the integrity of future CMVJ analyses, comparisons among various studies' results, or both.

Utility of peak torque and rate of torque development characteristics to identify walking performance ability in older women.

OBJECTIVES: It is unclear whether peak torque and rate of torque development (RTD) measurements can characterize functional differences in older adults according to their performance on a six-minute walk test. This study aimed to examine the efficacy of isometric peak torque and RTD characteristics of the knee extensors to differentiate between functional status in older women who are able (higher functioning) versus those who are unable (lower functioning) to walk 550 m in six minutes. METHODS: Ten higher functioning (67±4 years) and 10 lower functioning (68±4 years) older women performed three isometric knee extension maximal voluntary contractions followed by a six-minute walk test. Peak torque and early (RTD100), late (RTD200), and maximum (Peak RTD) RTD measurements were obtained from each contraction. RESULTS: The higher functioning group exhibited greater peak torque, Peak RTD, RTD100, and RTD200 compared to the lower functioning group (P≤0.011), with larger differences occurring for RTD characteristics (39.9-54.9%) than peak torque (20.3%). Multiple regression analysis indicated that RTD200 was the single best predictor of the distance covered during the six-minute walk test (R2=0.437, P=0.002). CONCLUSIONS: These findings suggest that knee extensor muscle strength, and in particular RTD, may be an effective discriminator and predictor of walking performance ability in older women.

One brick at a time: Building a developmental profile of spatial abilities.

Spatial abilities are not only fundamental for activities of daily living, but they are also markers of academic and professional success. It has remained a challenge, however, to understand their development across childhood and adolescence, partly because of the lack of spatial tasks that are appropriate across age groups. For example, the well-established paper-based mental rotation test (MRT) has been shown to be too difficult for children. In the current study, we tested girls and boys in three age groups: younger children (5-8-years-old), older children (9-12), and adolescents (13-17) on a hands-on visuospatial task using toy bricks: the brick-building task (BBT). Children completed a low- and a high-mental rotation demand (LMR and HMR) version of the BBT and the paper-based MRT. Correlations were found between all tasks. Children, especially females, found the HMR more challenging than the LMR condition, but all children successfully completed the BBT. In contrast, the MRT was too difficult for the younger children to solve performing at chance. Given this result and that the BBT is a game-like, 3D, interactive task, the BBT could be used to examine the biological and/or environmental factors that affect the early development of visuospatial abilities.

An evaluation of visuospatial skills using hands-on tasks.

Several tests of mental rotation ability have been used to investigate its development and the origins of sex differences. One of the most used tests is the mental rotation test (MRT) by Vandenberg and Kuse. A limitation of the MRT is that it is a pen-and-paper test with 2D images of 3D objects. This is a challenge to the ecological validity of the MRT because mental rotation typically involves physical 3D objects that are also physically manipulated. The purpose of the present study was to compare mental rotation ability as evaluated by the MRT to three new tasks with physical objects (toy bricks) that were physically manipulated. The different tasks allowed us to vary the processing demands on mental rotation while standardizing other aspects of the tasks. Fifty-nine females and twenty-eight males completed the LMR and HMR conditions (low- and high-mental rotation demands, respectively) of the brick building task (BBT), a visual search task, and the MRT. As demands on mental rotation for the BBT increased, performance decreased and a sex difference, with males outperforming females, increased. There were correlations between all tasks, but they were larger between the versions of the BBT with the MRT. The results suggest that spatial skill is an assembly of interrelated subskills and that the sex difference is sensitive to the demands on mental rotation and dimensionality crossing. The benefits of the BBT are that it is ecologically valid, avoids dimensionality crossing, and the demands on mental rotation can be manipulated.

Pre-crastination and procrastination effects occur in a reach-to-grasp task.

How do we decide which object to pick up when faced with two alternatives? Imagine one object is near, but needs to be carried a long distance, and the other object is far, but needs to be carried a short distance. You might predict that participants would favour the far object that needs to be carried a short distance. In other words, they would procrastinate and delay picking up an object to minimise physical effort. In actuality, participants prefer to carry the near object a long distance, which is called pre-crastination. Pre-crastination may be preferred to procrastination because picking up the first object hastens completion of the first goal of the task and, subsequently, decreases cognitive load. The goal of the current study was to further investigate the mechanisms of the pre-crastination effect. This was done by converting the primarily walking task used in the first study on pre-crastination to a reach-to-grasp task. This change enabled the measurement of the duration of information processing (i.e., reaction time) when participants decided which object to move. Surprisingly, participants exhibited a range of behaviours: about 40% pre-crastinated, 40% procrastinated, and 20% neither pre-crastinated nor procrastinated. We suggest that scaling the task down from a walking task to a reach-to-grasp task altered the physical effort, cognitive load, and the interaction between these task demands. This enabled some participants to pre-crastinate and others to procrastinate. There was an intriguing relationship between the duration of information processing and the behaviour of participants: participants with the shortest reaction time had the strongest tendency to pre-crastinate, and participants with the longest reaction time had the strongest tendency to procrastinate. These findings fit with the automatic pre-crastination response hypothesis; that the "decision" to pre-crastinate is automatic. This automaticity caused the short durations of information processing for participants who pre-crastinated. Participants who procrastinated had to, first, inhibit the automatic response to pre-crastinate, which caused long durations of information processing.

The left cerebral hemisphere may be dominant for the control of bimanual symmetric reach-to-grasp movements.

Previous research has established that the left cerebral hemisphere is dominant for the control of continuous bimanual movements. The lateralisation of motor control for discrete bimanual movements, in contrast, is underexplored. The purpose of the current study was to investigate which (if either) hemisphere is dominant for discrete bimanual movements. Twenty-one participants made bimanual reach-to-grasp movements towards pieces of candy. Participants grasped the candy to either place it in their mouths (grasp-to-eat) or in a receptacle near their mouths (grasp-to-place). Research has shown smaller maximum grip apertures (MGAs) for unimanual grasp-to-eat movements than unimanual grasp-to-place movements when controlled by the left hemisphere. In Experiment 1, participants made bimanual symmetric movements where both hands made grasp-to-eat or grasp-to-place movements. We hypothesised that a left hemisphere dominance for bimanual movements would cause smaller MGAs in both hands during bimanual grasp-to-eat movements compared to those in bimanual grasp-to-place movements. The results revealed that MGAs were indeed smaller for bimanual grasp-to-eat movements than grasp-to-place movements. This supports that the left hemisphere may be dominant for the control of bimanual symmetric movements, which agrees with studies on continuous bimanual movements. In Experiment 2, participants made bimanual asymmetric movements where one hand made a grasp-to-eat movement while the other hand made a grasp-to-place movement. The results failed to support the potential predictions of left hemisphere dominance, right hemisphere dominance, or contralateral control.

Complexity of movement preparation and the spatiotemporal coupling of bimanual reach-to-grasp movements.

There is a movement preparation cost for bimanual asymmetric reaching movements compared to bimanual symmetric movements. This is likely caused by the complex spatiotemporal coupling of bimanual asymmetric movements. The spatiotemporal coupling of bimanual reach-to-grasp movements has been investigated, but not the potential movement preparation costs. The purpose of the present study was to investigate the relationship between movement preparation costs and spatiotemporal coupling of reach-to-grasp movements. Twenty-four participants made unimanual, bimanual symmetric, and bimanual asymmetric reach-to-grasp movements in four-choice reaction time tasks. There was a movement preparation cost for bimanual symmetric reach-to-grasp movements compared to unimanual movements, which was not previously seen for reaching movements. Coordinating two symmetric grasps probably caused this bimanual symmetric cost, as we have previously shown that there is no bimanual symmetric cost for reaching movements. It was also surprising that the complexity of movement preparation was comparable for bimanual symmetric and asymmetric reach-to-grasp movements. However, the spatial coupling of bimanual asymmetric movements at movement initiation suggested that they were prepared as bimanual symmetric movements. Online control was then used to modify these symmetric reach-to-grasp movements into asymmetric movements. Preparing bimanual symmetric reach-to-grasp movements in advance instead of asymmetric movements likely prevented a bimanual asymmetric cost.

Bimanual joint action: correlated timing or "bimanual" movements accomplished by two people.

A crew of two rowing together in perfect synchrony is an example of a task that requires each performer to maintain meticulous timing when coordinating their movements with the other. At the individual level, temporal coordination of the limbs has been observed in bimanual pointing movements even when made to targets of different distance. Timing of the arms is not independent; rather there is a natural temporal coupling. The aim of this experiment was to investigate whether the temporal characteristics of pointing movements can be observed under joint conditions. Sixteen pairs of participants made short and long, unimanual and bimanual pointing movements. In the unimanual and bimanual solo conditions, participants made the movements alone. In the joint condition, each participant contributed one arm to the joint "bimanual" movements. Absolute temporal coupling at movement initiation and termination was measured by the differences in reaction time and total response time. Relative temporal coupling at movement initiation and termination was measured by correlating reaction time and total response time of the left and right limbs. Pointing movements had synchronous movement termination in the bimanual solo conditions and asynchronous termination in the unimanual solo and bimanual joint conditions. The initiation and termination of the arms were not correlated in the unimanual solo condition (initiation r = 0.01, termination r = 0.03). Small-to-medium correlations (r = 0.19, r = 0.24) were observed in the bimanual joint condition, and they were larger than the unimanual solo condition (p = 0.022, p = 0.063). As expected, there were large correlations in the bimanual solo conditions (r = 0.91, r = 0.81). Our findings suggest that absolute temporal coupling does not occur between individuals, but there is evidence for relative temporal coupling in the bimanual joint condition.

Trajectory analysis of discrete goal-directed pointing movements: How many trials are needed for reliable data?

A powerful tool in motor behavior research is trajectory analysis of discrete goal-directed pointing movements. The purpose of the present analysis was to estimate the minimum number of trials per participant required to achieve the conventional level of reliability for trajectory analysis. We analyzed basic measurements of movement and three common methods of trajectory analysis within the framework of generalizability theory. Generalizability studies were used to decompose the total variance of these variables into the percent contributions from person, trial, and the person-by-trial interaction. Decision studies were then used to determine the minimum number of trials required to achieve the conventional level of reliability. The number of trials per participant needed for reliable data of discrete goal-directed pointing movements depended on the dependent variable-for example, reaction times required six or ten trials, movement times required three trials, and constant error required 47 trials. For trajectory analysis, ten or fewer trials were required for reliable dependent variables during the first half of the movement (up to peak velocity or 70% of the displacement). The number of trials required for the second half of the movement rapidly increased to 47 trials at movement termination. This increase in the number of trials required for reliable analysis of the second half of the movement was indicative of online control. Finally, correlation analysis was performed with simulated correlations on subsets of trials, and all 32 trials were required. However, 18 trials might be used without a practically significant change in the correlations.

Effects of integrated feedback on discrete bimanual movements in choice reaction time.

The ability to coordinate the simultaneous movements of our arms is limited by a coalition of constraints. Some of these constraints can be overcome when the task conceptualisation is improved. The present study investigated how the movement preparation of bimanual reaching movements was affected by integrated visual feedback of the responses. Previous research has shown that the preparation of bimanual asymmetric movements takes longer than bimanual symmetric movements. The goal of the present study was to determine whether integrated, Lissajous feedback could eliminate this bimanual asymmetric cost. Fifteen participants made unimanual and bimanual symmetric and asymmetric reaches with separate feedback, where there was a cursor and a target for each hand. Participants also made bimanual symmetric and asymmetric movements with integrated feedback; a single cursor and a single target represented the locations and goals of both arms in this condition. The results showed a bimanual asymmetric cost with separate feedback, and that this cost persisted with integrated feedback. We suggest that integrated feedback improved continuous and discrete bimanual movements in other experiments by facilitating error detection and correction processes. We hypothesise that the bimanual asymmetric cost persisted in the present experiment because the uncertainty associated with choice reaction time prevented the facilitated error processing from improving the preparation of the next trial.

The violation of Fitts' Law: an examination of displacement biases and corrective submovements.

Fitts' Law holds that, to maintain accuracy, movement times of aiming movements must change as a result of varying degrees of movement difficulty. Recent evidence has emerged that aiming to a target located last in an array of placeholders results in a shorter movement time than would be expected by the Fitts' equation-a violation of Fitts' Law. It has been suggested that the violation emerges because the performer adopts an optimized movement strategy in which they partially pre-plan an action to the closest placeholder (undershoot the last placeholder) and rely on a secondary acceleration to propel the limb toward the last location when it is selected as the target (Glazebrook et al. in Hum Mov Sci 39:163-176, 2015). In the current study, we examine this proposal and further elucidate the processes underlying the violation by examining limb displacement and corrective submovements that occur when performers aim to different target locations. For our Main Study, participants executed discrete aiming movements in a five-placeholder array. We also reanalyzed data from a previously reported study in which participants aimed in placeholder and no-placeholder conditions (Blinch et al. in Exp Brain Res 223:505-515, 2012). The results showed the violation of Fitts' Law unfolded following peak velocity (online control). Further, the analysis showed that movements to the last target tended to overshoot and had a higher proportion of secondary submovements featuring a reversal than other categories of submovement (secondary accelerations, discontinuities). These findings indicate that the violation of Fitts' Law may, in fact, result from a strategic bias toward planning farther initial displacements of the limb which accommodates a shorter time in online control.

Unified nature of bimanual movements revealed by separating the preparation of each arm.

Movement preparation of bimanual asymmetric movements is longer than bimanual symmetric movements in choice reaction time conditions, even when movements are cued directly by illuminating the targets (Blinch et al. in Exp Brain Res 232(3):947-955, 2014). This bimanual asymmetric cost may be caused by increased processing demands on response programming, but this requires further investigation. The present experiment tested the demands on response programming for bimanual movements by temporally separating the preparation of each arm. This was achieved by precuing the target of one arm before the imperative stimulus. We asked: What was prepared in advance when one arm was precued? The answer to this question would suggest which process causes the bimanual asymmetric cost. Advance movement preparation was examined by comparing reaction times with and without a precue for the left target and by occasionally replacing the imperative stimulus with a loud, startling tone (120 dB). A startle tone releases whatever movement is prepared in advance with a much shorter reaction time than control trials (Carlsen et al. in Clin Neurophysiol 123(1):21-33, 2012). Participants made bimanual symmetric and asymmetric reaching movements in simple and 2-choice reaction time conditions and a condition with a precue for the left target. We found a bimanual asymmetric cost in 2-choice conditions, and the asymmetric cost was significantly smaller when the left target was precued. These results, and the results from startle trials, suggest (1) that the precued movement was not fully programmed but partially programmed before the imperative stimulus and (2) that the asymmetric cost was caused by increased processing demands on response programming. Overall, the results support the notion that bimanual movements are not the sum of two unimanual movements; instead, the two arms of a bimanual movement are unified into a functional unit. When one target is precued, this critical unification likely occurs during response programming.

Facilitation and interference during the preparation of bimanual movements: contributions from starting locations, movement amplitudes, and target locations.

Symmetric, target-directed, bimanual movements take less time to prepare than asymmetric movements (Diedrichsen et al. in Cerebral Cortex 16(12):1729-1738, 2006; Heuer and Klein in Psychol Res 70(4):229-244, 2006b). The preparation savings for symmetric movements may be related to the specification of symmetric amplitudes, target locations, or both. The goals of this study were to determine which symmetric movement parameters facilitate the preparation of bimanual movements and to compare the size of the facilitation for different parameters. Thirty participants performed bimanual reaching movements that varied in terms of the symmetry/asymmetry of starting locations, movement amplitudes, and target locations. Reaction time savings were examined by comparing movements that had one symmetric parameter (and two asymmetric parameters) to movements with all asymmetric parameters. We observed significant savings (~10 ms) for movements with symmetric amplitudes and movements with symmetric target locations. Reaction time costs were examined by comparing movements that had two asymmetric parameters (and one symmetric parameter) to movements with all symmetric parameters. We observed significant reaction time costs (~13 ms) for all movements with asymmetric amplitudes. These results suggest that movement preparation is facilitated when amplitudes or target locations are symmetric and that movement preparation suffers interference when amplitudes are asymmetric. The relative importance of the three parameters to movement preparation, from most to least important, is movement amplitudes, target locations, and then starting locations. Interference with asymmetric amplitudes or target locations may be caused by cross-talk between concurrent processes of parameter specification during response programming.

Comparing movement preparation of unimanual, bimanual symmetric, and bimanual asymmetric movements.

The goal of this study was to determine the process or processes most likely to be involved in reaction-time costs for spatially cued bimanual reaching. We used reaction time to measure the cost of bimanual symmetric movements compared to unimanual movements (a bimanual symmetric cost) and the cost for bimanual asymmetric movements compared to symmetric movements (a bimanual asymmetric cost). The results showed that reaction times were comparable for all types of movements in simple reaction time; that is, there was neither a bimanual symmetric cost nor an asymmetric cost. Therefore, unimanual, bimanual symmetric, and bimanual asymmetric movements have comparable complexity during response initiation. In choice conditions, there was no bimanual symmetric cost but there was a bimanual asymmetric cost, indicating that the preparation of asymmetric movements is more complex than symmetric movements. This asymmetric cost is likely the result of interference during response programming.