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.

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.

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.

Examining the Mechanisms of Internal and External Focus of Attention With Donders' Subtractive Method.

The goal of the current study was to measure the processing demands on the stages of information processing with internal and external foci of attention. Participants completed simple and two-choice reaction time tasks with internal and external foci of attention. Donders' subtraction method was used to isolate the cumulative duration of stages unique to simple and choice reaction time tasks. Mean reaction time was comparable with internal and external foci of attention in simple and two-choice reaction time tasks. These results suggest that processing demands were comparable with internal and external foci of attention. We hypothesize that there was not a processing advantage for an external focus in simple reaction time because the required movements had low movement complexity.

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.

Investigating information processing of the bimanual asymmetric cost with the response priming technique.

Constraining the degrees of freedom simplifies the coordinative challenge of bimanual asymmetric movements. This, however, comes at the cost of increased processing demands during movement preparation, referred to as the bimanual asymmetric cost. The goal of the present study was to further investigate information processing of the bimanual asymmetric cost with the response priming technique. This technique involved precuing a movement to encourage it to be preprogrammed. A different movement is occasionally cued by the go signal, which required the preprogrammed movement to be reprogrammed. In Experiment 1, 2 preprogrammed unimanual movements were reprogrammed, or integrated, into a bimanual movement. In Experiment 2, a preprogrammed bimanual movement was reprogrammed, or de-integrated, into a unimanual movement. Both experiments revealed 2 costs when integrating or de-integrating bimanual movements. One cost was likely related to aborting 1 movement and preparing another, which is the typical reprogramming cost found in response priming experiments. The second cost was likely related to constraining the degrees of freedom of bimanual asymmetric movements, which is a bimanual asymmetric cost. Integrating 2 unimanual movements into a bimanual asymmetric movement involves constraining the degrees of freedom, and de-integrating a bimanual asymmetric movement into a unimanual movement involves unconstraining the degrees of freedom. Both reprogramming and bimanual asymmetric costs occurred in 1 of the experimental conditions, and the interesting finding was that their effects were additive. Additive costs suggest that each cost affects a different stage of movement preparation. We suggest that the bimanual asymmetric cost occurs during response selection. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Real-time measurement of isometric peak torque and rate of torque development using a novel strength testing device: a validity and reliability study.

Objective: Isometric peak torque (PT) and rate of torque development (RTD) are important characteristics relevant to athletic performance. A novel device called the Dynamo Torque Analyzer calculates and displays real-time measurements of isometric PT and RTD. However, the ability of the Dynamo to provide valid and reliable isometric PT and RTD measurements similar to those of an isokinetic dynamometer remains unclear. This study aimed to compare the reliability and magnitude of isometric leg extension and flexion PT and RTD measurements between an isokinetic dynamometer and the Dynamo Torque Analyzer.Approach: Twenty healthy, recreationally-active adults (age = 22 ± 3 years; height = 169 ± 10 cm; mass = 71 ± 18 kg) performed three isometric leg extension and flexion maximal voluntary contractions on two different occasions, from which isometric PT and early (RTD100), late (RTD200), and maximum (Peak RTD) RTD characteristics were measured by an isokinetic dynamometer and the Dynamo.Main results: Isometric leg extension and flexion PT and RTD characteristics were highly consistent across sessions for both the isokinetic dynamometer and Dynamo devices, with intraclass correlation coefficients of 0.935-0.984 and standard errors of measurement expressed as a percentage of the mean of 4.93-14.46%. There were significant positive relationships between the isokinetic dynamometer and Dynamo for all PT and RTD characteristics (r≥ 0.994;P< 0.001). Moreover, no significant differences between devices were observed for these variables (P= 0.107-0.555).Significance: These findings suggest that the Dynamo Torque Analyzer may be a valid and reliable device for measuring isometric PT and RTD of the lower-body musculature.

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.

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.

Focus of attention effects on lower extremity biomechanics during vertical jump landings.

This study examined biomechanical differences between external and internal foci of attention during vertical jump landings in males and females. Twenty-four healthy adults performed eight vertical jump landings using both internal and external foci while three-dimensional kinematic and ground reaction force (GRF) data were obtained. Two (focus) by two (sex) analyses of variance (α = 0.05) and Cohen's d effect sizes (ES) were used to compare differences in vertical GRF, joint angular positions and displacements, and lower limb joint angular work between foci and between sexes. Significantly greater knee contributions to total angular work occurred during external versus internal focus landings regardless of sex (p = .013; ES = 0.30). Significantly smaller plantarflexion angles (p = .019; ES = 0.53) and significantly greater knee flexion angles were observed at ground contact (p < .001; ES = 1.11) in males during external focus landings. Females exhibited significantly smaller knee flexion angles at both ground contact during external versus internal focus landings (p = .031; ES = 0.20) and compared to males during external focus landings (p < .001; ES = 1.76). Both peak vertical GRF (p = .003; ES = 1.54) and the ankle contributions to total angular work during loading (p = .026; ES = 1.07) were greater in females versus males regardless of foci, whereas the knee contributions to total angular work during loading were smaller in women (p = .026; ES = 1.07). Males and females might consider adopting an external focus during vertical jump landings to increase knee joint contributions to lower limb energy absorption. Females, in particular, might consider external focus use to decrease peak vertical GRF and increase the knee joint's contribution to total energy absorption to magnitudes similar to those exhibited by males.

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.

Effects of integrated feedback and movement templates on discrete bimanual movements in simple reaction time.

The purpose of the current study was to investigate whether integrated visual feedback and movement templates could facilitate bimanual movements with different patterns of spatiotemporal coupling and decoupling. Knowing when Lissajous feedback and movement templates improve bimanual movements, and when they do not, will help determine the mechanisms of task conceptualisation. We tested two bimanual asymmetric conditions where different movement templates were used to encourage the movements to travel different paths to the same targets. The asymmetric straight condition was the same as Shea, Boyle, and Kovacs (2012), and we predicted that we would replicate their results and find no temporal coupling. The novel asymmetric diagonal condition required movements with a 2:1 movement ratio (relative spatiotemporal coupling). Longer movement time and larger root-mean-square deviation of the trajectories suggested that asymmetric straight movements were more difficult than symmetric movements. Even longer movement times and fewer target hits suggested that asymmetric diagonal movements were more difficult than asymmetric straight movements. Lissajous feedback and movement templates made the difficult asymmetric movements possible. However, movements with relative spatiotemporal coupling were the most difficult and movements without temporal coupling were still more difficult than symmetric movements. We suggest that Lissajous feedback and movement templates improved the task conceptualisation, which eliminated or reduced the high-level cognitive constraints. The low-level neuromuscular constraints, however, persisted and these caused the increased difficulty for asymmetric movements. Improving the task conceptualisation can facilitate asymmetric movements. These asymmetric movements still have different difficulties and they are not as easy as symmetric movements.

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.

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.

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.