Visual salience of 3D and 2D spoons determines S-R mapping and flanker effects.

This study tested the hypothesis that affordances for grasping with the corresponding hand are activated more strongly by three-dimensional (3D) real objects than by two-dimensional (2D) pictures of the objects. In Experiment 1, participants made left and right keypress responses to the handle or functional end (tip) of an eating utensil using compatible and incompatible mappings. In one session, stimuli were spoons mounted horizontally on a blackboard with the sides to which the handle and tip pointed varying randomly.

Visual salience, not the graspable part of a pictured eating utensil, grabs attention.

Three experiments used compatible and incompatible mappings of images of eating utensils to test the hypothesis that these images activate affordances for grasping with the corresponding hand when the required response is a key-press. In Experiment 1, stimuli were photographs of a plastic spoon oriented on the horizontal axis, with the handle location varying randomly between left and right. Participants were instructed to respond to the handle or the tip, with a compatible mapping in one trial block and an incompatible mapping in another.

An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability.

Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture.

Deficits in Coordinative Bimanual Timing Precision in Children With Specific Language Impairment.

Purpose: Our objective was to delineate components of motor performance in specific language impairment (SLI); specifically, whether deficits in timing precision in one effector (unimanual tapping) and in two effectors (bimanual clapping) are observed in young children with SLI.

Method: Twenty-seven 4- to 5-year-old children with SLI and 21 age-matched peers with typical language development participated. All children engaged in a unimanual tapping and a bimanual clapping timing task.

The efficacy of the Microsoft Kinect to assess human bimanual coordination.

The Microsoft Kinect has been used in studies examining posture and gait. Despite the advantages of portability and low cost, this device has not been used to assess interlimb coordination. Fundamental insights into movement control, variability, health, and functional status can be gained by examining coordination patterns.

Action-specific judgment, not perception: Fitts' law performance is related to estimates of target width only when participants are given a performance score.

Proponents of the action-specific account of perception and action posit that participants perceive their environment relative to their capabilities. For example, softball players who batted well judge the ball as being larger compared to players who did not hit as well. In the present study, we examined this issue in the context of a well-known speed-accuracy movement task that can be examined in the laboratory, repetitive Fitts aiming.

Limit cycle oscillations in standing human posture.

Limit cycle oscillations (LCOs) are a hallmark of dynamic instability in time-delayed and nonlinear systems such as climate change models, biological oscillators, and robotics. Here we study the links between the human neuromuscular system and LCOs in standing posture. First, we demonstrate through a simple mathematical model that the observation of LCOs in posture is indicative of excessive neuromuscular time-delay.

The relationship between intermittent limit cycles and postural instability associated with Parkinson's disease.

Background: Many disease-specific factors such as muscular weakness, increased muscle stiffness, varying postural strategies, and changes in postural reflexes have been shown to lead to postural instability and fall risk in people with Parkinson's disease (PD). Recently, analytical techniques, inspired by the dynamical systems perspective on movement control and coordination, have been used to examine the mechanisms underlying the dynamics of postural declines and the emergence of postural instabilities in people with PD.

Methods: A wavelet-based technique was used to identify limit cycle oscillations (LCOs) in the anterior-posterior (AP) postural sway of people with mild PD ( = 10) compared to age-matched controls ( = 10).

Dynamic stability of a human standing on a balance board.

The neuromuscular system used to stabilize upright posture in humans is a nonlinear dynamical system with time delays. The analysis of this system is important for improving balance and for early diagnosis of neuromuscular disease. In this work, we study the dynamic coupling between the neuromuscular system and a balance board-an unstable platform often used to improve balance in young athletes, and older or neurologically impaired patients.

The distinction between tapping and circle drawing with and without tactile feedback: an examination of the sources of timing variance.

An internal clock-like process has been implicated in the control of rhythmic movements performed for short (250-2,000 ms) time scales. However, in the past decade, it has been claimed that a clock-like central timing mechanism is not required for smooth cyclical movements. The distinguishing characteristic delineating clock-like (event) from non-clock-like (emergent) timing is thought to be the kinematic differences between tapping (discrete-like) and circle drawing (smooth).

Motor timing deficits in children with Attention-Deficit/Hyperactivity disorder.

Children with Attention-Deficit/Hyperactivity Disorder (ADHD) are thought to have fundamental deficits in the allocation of attention for information processing. Furthermore, it is believed that these children possess a fundamental difficulty in motoric timing, an assertion that has been explored recently in adults and children. In the present study we extend this recent work by fully exploring the classic Wing and Kristofferson (1973) analysis of timing with typically developing children (n=24) and children with ADHD (n=27).

Physically coupling two objects in a bimanual task alters kinematics but not end-state comfort.

People often grasp objects with an awkward grip to ensure a comfortable hand posture at the end of the movement. This end-state comfort effect is a predominant constraint during unimanual movements. However, during bimanual movements the tendency for both hands to satisfy end-state comfort is affected by factors such as end-orientation congruency and task context.

Circle drawing does not exhibit auditory-motor synchronization.

Differences in timing control processes between tapping and circle drawing have been extensively documented during continuation timing. Differences between event and emergent control processes have also been documented for synchronization timing using emergent tasks that have minimal event-related information. However, it is not known whether the original circle-drawing task also behaves differently than tapping during synchronization.

Long-range correlation properties in motor timing are individual and task specific.

1/f (β) noise represents a specific form of (long-range) correlations in a time series that is pervasive across many sensorimotor variables. Recent studies have shown that the precise properties of the correlations demonstrated by a group of test participants may vary as a function of experimental conditions or factors characterizing the group. Our purpose in the present study was to clarify whether long-range correlations affect sensorimotor performance generally or in a task-specific manner and whether each individual produces characteristic long-range correlations that are reliable across several runs of the same task.

Synchronization in repetitive smooth movement requires perceptible events.

Accurate timing performance during auditory-motor synchronization has been well documented for finger tapping tasks. It is believed that information pertaining to an event in movement production aids in detecting and correcting for errors between movement cycle completion and the metronome tone. Tasks with minimal event-related information exhibit more variable synchronization and less rapid error correction.

Human motor transfer is determined by the scaling of size and accuracy of movement.

A transfer of training design was used to examine the role of the Index of Difficulty (ID) on transfer of learning in a sequential Fitts's law task. Specifically, the role of the ratio between the accuracy and size of movement (ID) in transfer was examined. Transfer of skilled movement is better when both the size and accuracy of movement are changed by the same factor (ID is constant) than when only size or accuracy is changed.

Timing processes are correlated when tasks share a salient event.

Event timing is manifested when participants make discrete movements such as repeatedly tapping a key. Emergent timing is manifested when participants make continuous movements such as repeatedly drawing a circle. Here we pursued the possibility that providing salient perceptual events to mark the completion of time intervals could allow circle drawing and tapping to share a common timing process.

Generalized motor abilities and timing behavior in children with specific language impairment.

Purpose: To examine whether children with specific language impairment (SLI) differ from normally developing peers in motor skills, especially those skills related to timing.

Method: Standard measures of gross and fine motor development were obtained. Furthermore, finger and hand movements were recorded while children engaged in 4 different timing tasks, including tapping and drawing circles in time with a metronome or a visual target.

Evidence that a motor timing deficit is a factor in the development of stuttering.

Purpose: To determine whether young children who stutter have a basic motor timing and/or a coordination deficit.

Method: Between-hands coordination and variability of rhythmic motor timing were assessed in 17 children who stutter (4-6 years of age) and 13 age-matched controls. Children clapped in rhythm with a metronome with a 600-ms interbeat interval and then attempted to continue to match this target rate for 32 unpaced claps.

Distinct timing mechanisms are implicated in distinct circle drawing tasks.

That individual timing variability is correlated across some tasks but not others has instigated the notion of distinct timing processes, referred to as 'event' timing and 'emergent' timing for tasks with and without salient events, respectively. The delineation of the event-emergent framework owes much to the circle drawing task as it can be performed with or without such events, all other factors being equal. We investigated continuous and intermittent circle drawing from a principled perspective allowing for the classification of timing mechanisms based on mathematical theorems.

Multiple timescales in postural dynamics associated with vision and a secondary task are revealed by wavelet analysis.

Discrete wavelet analysis is used to resolve the center of pressure time series data into several timescale components, providing new insights into postural control. Healthy young and elderly participants stood quietly with their eyes open or closed and either performed a secondary task or stood quietly. Without vision, both younger and older participants had reduced energy in the long timescales, supporting the concept that vision is used to control low frequency postural sway.

Distinct timing mechanisms produce discrete and continuous movements.

The differentiation of discrete and continuous movement is one of the pillars of motor behavior classification. Discrete movements have a definite beginning and end, whereas continuous movements do not have such discriminable end points. In the past decade there has been vigorous debate whether this classification implies different control processes.

The influence of dominant versus non-dominant hand on event and emergent motor timing.

It has been hypothesized that timing in tapping utilizes event timing; a clock-like process, whereas timing in circle drawing is emergent. Three experiments examined timing in tapping and circle drawing by the dominant and non-dominant hand. Participants were right-hand dominant college aged males and females.

Timing precision in circle drawing does not depend on spatial precision of the timing target.

The authors manipulated the width of a timing target in continuous circle drawing to determine whether a more stringent spatial-timing criterion would produce an increase in participants' (N = 30) temporal variability. They also examined the effect of the computational method of determining cycle duration. There was no effect of spatial precision on temporal variability in circle drawing, and tapping and circle drawing were found to use the same criterion.