Search

Movement systems are massively redundant, and there are always multiple movement solutions to any task demand; motor abundance. Movement consequently exhibits 'repetition without repetition', where movement outcomes are preserved but the kinematic details of the movement vary across repetitions. The uncontrolled manifold (UCM) concept is one of several methods that analyses movement variability with respect to task goals, to quantify repetition without repetition and test hypotheses about the control architecture producing a given abundant response to a task demand. However, like all these methods, UCM is under-constrained in how it decomposes a task and performance. In this paper, we propose and test a theoretical framework for constraining UCM analysis, specifically the perception of task-dynamical affordances. Participants threw tennis balls to hit a target set at 5m, 10m or 15m, and we performed UCM analysis on the shoulder-elbow-wrist joint angles with respect to variables derived from an affordance analysis of this task as well as more typical biomechanical variables. The affordance-based UCM analysis performed well, although data also showed thrower dynamics (effectivities) need to be accounted for as well. We discuss how the theoretical framework of affordances and affordance-based control can be connected to motor abundance methods in the future. [ABSTRACT FROM AUTHOR]

Objective: To evaluate harms reporting in systematic reviews (SRs) of microvascular free flap (MFF) in head and neck reconstruction. Data Sources: This cross‐sectional analysis included searches from the following major databases from 2012 to June 1, 2022: MEDLINE (Pubmed and Ovid), Embase, Epistemonikos, and the Cochrane Database of Systematic Reviews. Review Methods: In a masked duplicate manner, screening was performed using Rayyan, and data were extracted using a pilot‐tested Google form. A MeaSurement Tool to Assess systematic Reviews‐2 (AMSTAR‐2) was used to appraise the methodological quality of reviews and the corrected covered area was calculated to detect primary study overlap across all reviews. Reviews were then grouped in pairs of 2, called dyads, and the corrected covered area was calculated again for each individual dyad. Dyads with high overlap (≥50%) were further investigated for the accuracy of harms reporting. Results: Our initial search yielded 268 records, with 50 SRs meeting the inclusion criteria. A total of 46 (92%) of the included reviews demonstrated 50% or more adherence to the items assessed in our harms checklist. Our corrected covered area tool revealed 0.6% primary study overlap across all reviews, and 1 dyad with high overlap (≥50%). No statistically significant relationship was observed between the completeness of harms reporting and reviews listing harms as a primary outcome, reviews reporting adherence to Preferred Reporting Items of Systematic Reviews and Meta‐Analyses, or a review's AMSTAR rating. Conclusion: This study identifies how harms reporting in SRs of MFF reconstruction of the head and neck can be improved and provides suggestions with the potential to mitigate the paucity in current literature. [ABSTRACT FROM AUTHOR]

Coordinated rhythmic movement is specifically structured in humans. Movement at 0[degrees] mean relative phase is maximally stable, 180[degrees] is less stable, and other coordinations can, but must, be learned. Variations in perceptual ability play a key role in determining the observed stabilities so we investigated whether stable movements can be acquired by improving perceptual ability. We assessed movement stability in Baseline, Post Training, and Retention sessions by having participants use a joystick to coordinate the movement of two dots on a screen at three relative phases. Perceptual ability was also assessed using a two-alternative forced choice task in which participants identified a target phase of 90[degrees] in a pair of displays. Participants then trained with progressively harder perceptual discriminations around 90[degrees] with feedback. Improved perceptual discrimination of 90[degrees] led to improved performance in the movement task at 90[degrees] with no training in the movement task. The improvement persisted until Retention without further exposure to either task. A control group's movement stability did not improve. Movement stability is a function of perceptual ability, and information is an integral part of the organization of this dynamical system. (Contains 1 footnote, 1 table, and 3 figures.)

Grip selection tasks have been used to test "planning" in both autism and developmental coordination disorder (DCD). We differentiate between "motor" and "executive" planning and present a modified motor planning task. Participants grasped a cylinder in 1 of 2 orientations before turning it clockwise or anticlockwise. The rotation resulted in a comfortable final posture at the cost of a harder initial reaching action on 50% of trials. We hypothesized that grip selection would be dominated by motoric developmental status. Adults were always biased towards a comfortable end-state with their dominant hand, but occasionally ended uncomfortably with their nondominant hand. Most 9- to 14-year-olds with and without autism also showed this "end-state comfort" bias but only 50% of 5- to 8-year-olds. In contrast, children with DCD were biased towards selecting the simplest initial movement. Our results are best understood in terms of "motor" planning, with selection of an easier initial grip resulting from poor reach-to-grasp control rather than an executive planning deficit. The absence of differences between autism and controls may reflect the low demand this particular task places on executive planning. (Contains 2 figures.)

Aim: This study investigated the nature of coordination and control problems in children with developmental coordination disorder (DCD). Method: Seven adults (two males, five females, age range 20-28y; mean 23y, SD 2y 8mo) and eight children with DCD (six males, two females, age range 7-9y; mean 8y, SD 8mo), and 10 without DCD (seven males, three females, age range 7-9y; mean 8y, SD 7mo) sat in a swivel chair and looked at or pointed to targets. Optoelectronic apparatus recorded head, torso, and hand movements, and the spatial and temporal characteristics of the movements were computed. Results: Head movement times were longer (p less than 0.05) in children with DCD than in the comparison group, even in the looking task, suggesting that these children experience problems at the lowest level of coordination (the coupling of synergistic muscle groups within a single degree of freedom). Increasing the task demands with the pointing condition affected the performance of children with DCD to a much greater extent than the other groups, most noticeably in key feedforward kinematic landmarks. Temporal coordination data indicated that all three groups attempted to produce similar movement patterns to each other, but that the children with DCD were much less successful than age-matched children in the comparison group. Interpretation: Children with DCD have difficulty coordinating and controlling single degree-of-freedom movements; this problem makes more complex tasks disproportionately difficult for them. Quantitative analysis of kinematics provides key insights into the nature of the problems faced by children with DCD.

Ideomotor (IM) theory suggests that observing someone else perform an action activates an internal motor representation of that behaviour within the observer. Evidence supporting the case for an ideomotor theory of imitation has come from studies that show imitative responses to be faster than the same behavioural measures performed in response to spatial cues. In an attempt to replicate these findings, we manipulated the salience of the visual cue and found that we could reverse the advantage of the imitative cue over the spatial cue. We suggest that participants utilised a simple visuomotor mechanism to perform all aspects of this task, with performance being driven by the relative visual salience of the stimuli. Imitation is a more complex motor skill that would constitute an inefficient strategy for rapid performance.

Coordinated rhythmic movement is specifically structured in humans. Movement at 0[degrees] mean relative phase is maximally stable, 180[degrees] is less stable, and other coordinations can, but must, be learned. Variations in perceptual ability play a key role in determining the observed stabilities so we investigated whether stable movements can be acquired by improving perceptual ability. We assessed movement stability in Baseline, Post Training, and Retention sessions by having participants use a joystick to coordinate the movement of two dots on a screen at three relative phases. Perceptual ability was also assessed using a two-alternative forced choice task in which participants identified a target phase of 90[degrees] in a pair of displays. Participants then trained with progressively harder perceptual discriminations around 90[degrees] with feedback. Improved perceptual discrimination of 90[degrees] led to improved performance in the movement task at 90[degrees] with no training in the movement task. The improvement persisted until Retention without further exposure to either task. A control group's movement stability did not improve. Movement stability is a function of perceptual ability, and information is an integral part of the organization of this dynamical system. Keywords: perception-action, rhythmic movement coordination, perceptual learning, movement stability DOI: 10.1037/a0020412

Grip selection tasks have been used to test 'planning' in both autism and developmental coordination disorder (DCD). We differentiate between motor and executive planning and present a modified motor planning task. Participants grasped a cylinder in 1 of 2 orientations before turning it clockwise or anticlockwise. The rotation resulted in a comfortable final posture at the cost of a harder initial reaching action on 50% of trials. We hypothesized that grip selection would be dominated by motoric developmental status. Adults were always biased towards a comfortable end-state with their dominant hand, but occasionally ended uncomfortably with their nondominant hand. Most 9- to 14-year-olds with and without autism also showed this 'end-state comfort' bias but only 50% of 5- to 8-year-olds. In contrast, children with DCD were biased towards selecting the simplest initial movement. Our results are best understood in terms of motor planning, with selection of an easier initial grip resulting from poor reach-to-grasp control rather than an executive planning deficit. The absence of differences between autism and controls may reflect the low demand this particular task places on executive planning. Keywords: motor planning, grip selection, bias, prehension, coordination, autism, DCD DOI: 10.1037/a0017177

ABSTRACT. Action selection is subject to many biases. Immediate movement history is one such bias seen in young infants. Is this bias strong enough to affect adult behavior? Adult participants [...]

Previous work has established that judgments of relative phase variability of 2 visually presented oscillators covary with mean relative phase. Ninety degrees is judged to be more variable than 0[degree] or 180[degrees], independently of the actual level of phase variability. Judged levels of variability also increase at 180[degrees]. This pattern of judgments matches the pattern of movement coordination results. Here, participants judged the phase variability of their own finger movements, which they generated by actively tracking a manipulandum moving at 0[degree], 90[degrees], or 180[degrees], and with 1 of 4 levels of Phase Variability. Judgments covaried as an inverted U-shaped function of mean relative phase. With an increase in frequency, 180[degrees] was judged more variable whereas 0[degrees] was not. Higher frequency also reduced discrimination of the levels of Phase Variability. This matching of the proprioceptive and visual results, and of both to movement results, supports the hypothesized role of online perception in the coupling of limb movements. Differences in the 2 cases are discussed as due primarily to the different sensitivities of the systems to the information.

A recent philosophical literature has developed a taxonomy of scientific explanations, models, and the two basic research programmes that produce them. The first programme takes some capacity of a system and maps out how it works by breaking it down into various sub-capacities, each with their own distinct characteristics. The end goal is a functional model, a 'how-possibly' box-and-arrow type map of the functional organisation of the capacity. The second programme instead focuses on analytically decomposing a proposed mechanism that produces a phenomenon into real parts and processes. The end goal is a dynamical mechanistic model, a 'how-actually' explanation in which each model part explicitly represents the dynamics of those real parts or processes. Mechanistic models are better explanations of phenomena. Ecological psychology has, so far, widely resisted becoming a mechanistic science. This is in part due to our objections to mechanistic, Cartesian ontologies, and more recently because it's not clear we can meaningfully decompose the systems we study in order to develop such models. I will argue here that both of these concerns are unfounded, that ecological psychology is actually perfectly capable of developing mechanistic models, and that therefore we should do so, in order to gain the benefits. [ABSTRACT FROM AUTHOR]

A state-based technique for the representation and recognition of gesture is presented. We define a gesture to be a sequence of states in a measurement or configuration space. For a given gesture, these states are used to capture both the repeatability and variability evidenced in a training set of example trajectories. Using techniques for computing a prototype trajectory of an ensemble of trajectories, we develop methods for defining configuration states along the prototype and for recognizing gestures from an unsegmented, continuous stream of sensor data. The approach is illustrated by application to a range of gesture-related sensory data: the two-dimensional movements of a mouse input device, the movement of the hand measured by a magnetic spatial position and orientation sensor, and, lastly, the changing eigenvector projection coefficients computed from an image sequence. Index Terms - Gesture recognition, state-based representation, gesture prototype, motion-based recognition.

Interface theory is the hypothesis that inferential, representational theories of perception entail that fitness, not truth, dictates the evolution of perceptual systems. They show, with simulations, that "veridical" perceptual mappings (ones that preserve at least some of the structure of the world) are routinely out-competed by "non-veridical" interfaces (ones that make no attempt to preserve that structure). They therefore take particular aim at the direct perception, ecological approach to perception and work to show that such a system, even if technically an option, would never be selected for by evolution. This paper defends the ecological approach from this novel, existential attack by showing that the ecological hypothesis is so different in kind to the inferential, representational view of perception that it simply falls outside the scope of interface theory's critiques; ecological psychology remains a viable scientific endeavor. This analysis will show that, far from being a radical new approach to perception, interface theory is simply a clear and elegant formalization of mainstream representational psychology, and any implications interface theory may have belong solely to that branch of science. [ABSTRACT FROM AUTHOR]

Research spanning 100 years has revealed that learning a novel perception-action task is remarkably task-specific. With only a few exceptions, transfer is typically very small, even with seemingly small changes to the task. This fact has remained surprising given previous attempts to formalise the notion of what a task is, which have been dominated by common-sense divisions of tasks into parts. This article lays out an ecologically grounded alternative, ecological task dynamics , which provides us with tools to formally define tasks as experience from the first-person perspective of the learner. We explain this approach using data from a learning and transfer experiment using bimanual coordinated rhythmic movement as the task, and acquiring a novel coordination as the goal of learning. 10 participants were extensively trained to perform 60° mean relative phase; this learning transferred to 30° and 90°, against predictions derived from our previous work. We use recent developments in the formal model of the task to guide interpretation of the learning and transfer results. [ABSTRACT FROM AUTHOR]

Moving in time together has been shown to cultivate pro-social effects in co-actors, such as cooperation and helping. But less is known about who these effects apply to – whether they are restricted only to co-actors, or whether they generalize to those not involved in the coordination. One difference between past work finding generalized vs. restricted effects is whether these "outsiders" were present for the coordination or not. The present study explores whether the pro-social effects of coordination are seen towards observers as well as co-actors, and whether the absence or presence of observers during the coordination is a determining factor. Results show that greater cooperation following coordination is only seen amongst co- actors, regardless of whether the observers were present during the task or not. Findings are discussed in the context of the literature and alternative explanations for research showing generalized effects are suggested. [ABSTRACT FROM AUTHOR]