Affordances for throwing: An uncontrolled manifold analysis.

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.

Reduced learning rates but successful learning of a coordinated rhythmic movement by older adults.

Previous work has investigated the information-based mechanism for learning and transfer of learning in coordinated rhythmic movements. In those papers, we trained young adults to produce either 90° or 60° and showed in both cases that learning entailed learning to use relative position as information for the relative phase. This variable then supported transfer of learning to untrained coordinations +/30° on either side. In this article, we replicate the 90° study with younger adults and extend it by training older adults (aged between 55 and 65 years). Other work has revealed a steep decline in learning rate around this age, and no follow-up study has been able to successfully train older adults to perform a novel coordination. We used a more intensive training paradigm and showed that while older adult learning rates remain about half that of younger adults, given time they are able to acquire the new coordination. They also learn to use relative position, and consequently show the same pattern of transfer. We discuss implications for attempts to model the process of learning in this task.

Harms Reporting in Systematic Reviews of the Microvascular Free Flap in Head and Neck Reconstruction.

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.

The Ecological Task Dynamics of Learning and Transfer in Coordinated Rhythmic Movement.

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.

Decision-making process for introduction of maternal vaccines in Kenya, 2017-2018.

BACKGROUND: Maternal immunization is a key strategy for reducing morbidity and mortality associated with infectious diseases in mothers and their newborns. Recent developments in the science and safety of maternal vaccinations have made possible development of new maternal vaccines ready for introduction in low- and middle-income countries. Decisions at the policy level remain the entry point for maternal immunization programs. We describe the policy and decision-making process in Kenya for the introduction of new vaccines, with particular emphasis on maternal vaccines, and identify opportunities to improve vaccine policy formulation and implementation process. METHODS: We conducted 29 formal interviews with government officials and policy makers, including high-level officials at the Kenya National Immunization Technical Advisory Group, and Ministry of Health officials at national and county levels. All interviews were recorded and transcribed. We analyzed the qualitative data using NVivo 11.0 software. RESULTS: All key informants understood the vaccine policy formulation and implementation processes, although national officials appeared more informed compared to county officials. County officials reported feeling left out of policy development. The recent health system decentralization had both positive and negative impacts on the policy process; however, the negative impacts outweighed the positive impacts. Other factors outside vaccine policy environment such as rumours, sociocultural practices, and anti-vaccine campaigns influenced the policy development and implementation process. CONCLUSIONS: Public policy development process is complex and multifaceted by its nature. As Kenya prepares for introduction of other maternal vaccines, it is important that the identified policy gaps and challenges are addressed.

Perceptual information supports transfer of learning in coordinated rhythmic movement.

In this paper, we trained people to produce 90° mean relative phase using task-appropriate feedback and investigated whether and how that learning transfers to other coordinations. Past work has failed to find transfer of learning to other relative phases, only to symmetry partners (identical coordinations with reversed lead-lag relationships) and to other effector combinations. However, that research has all trained people using transformed visual feedback (visual metronomes, Lissajous feedback) which removes the relative motion information typically used to produce various coordinations (relative direction, relative position; Wilson and Bingham, in Percept Psychophys 70(3):465-476, 2008). Coordination feedback (Wilson et al., in J Exp Psychol Hum Percept Perform 36(6):1508, 2010) preserves that information and we have recently shown that relative position supports transfer of learning between unimanual and bimanual performance of 90° (Snapp-Childs et al., in Exp Brain Res 233(7), 2225-2238, 2015). Here, we ask whether that information can support the production of other relative phases. We found large, asymmetric transfer of learning bimanual 90° to bimanual 60° and 120°, supported by perceptual learning of relative position information at 90°. For learning to transfer, the two tasks must overlap in some critical way; this is additional evidence that this overlap must be informational. We discuss the results in the context of an ecological, task dynamical approach to understanding the nature of perception-action tasks.

Knowledge and attitudes towards influenza and influenza vaccination among pregnant women in Kenya.

BACKGROUND: Influenza vaccination during pregnancy benefits mothers and children. Kenya and other low- and middle-income countries have no official influenza vaccination policies to date but are moving towards issuing such policies. Understanding determinants of influenza vaccine uptake during pregnancy in these settings is important to inform policy decisions and vaccination rollout. METHODS: We interviewed a convenience sample of women at antenatal care facilities in four counties (Nairobi, Mombasa, Marsabit, Siaya) in Kenya. We described knowledge and attitudes regarding influenza vaccination and assessed factors associated with willingness to receive influenza vaccine. RESULTS: We enrolled 507 pregnant women, median age was 26 years (range 15-43). Almost half (n = 240) had primary or no education. Overall, 369 (72.8%) women had heard of influenza. Among those, 288 (78.1%) believed that a pregnant woman would be protected if vaccinated, 252 (68.3%) thought it was safe to receive a vaccine while pregnant, and 223 (60.4%) believed a baby would be protected if mother was vaccinated. If given opportunity, 309 (83.7%) pregnant women were willing to receive the vaccine. Factors associated with willingness to receive influenza vaccine were mothers' belief in protective effect (OR 3.87; 95% CI 1.56, 9.59) and safety (OR 5.32; 95% CI 2.35, 12.01) of influenza vaccines during pregnancy. CONCLUSION: Approximately one third of pregnant women interviewed had never heard of influenza. Willingness to receive influenza vaccine was high among women who had heard about influenza. If the Kenyan government recommends influenza vaccine for pregnant women, mitigation of safety concerns and education on the benefits of vaccination could be the most effective strategies to improve vaccine acceptance.

I'll just watch: Do the pro-social effects of coordination really generalize to non-actors?

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.

Intraoperative Tissue Perfusion Measurement by Laser Speckle Imaging: A Potential Aid for Reducing Postoperative Complications in Free Flap Breast Reconstruction.

Adequate tissue perfusion is essential to minimize postoperative complications following microsurgery. Intraoperative knowledge of tissue perfusion could aid surgical decision-making and result in reduced complications. Laser speckle imaging is a new, noninvasive technique for mapping tissue perfusion. This article discusses the feasibility of using laser speckle imaging during free flap breast reconstruction and its potential to identify areas of inadequate perfusion, thus reducing surgical complications. Adult patients scheduled to undergo free flap breast reconstruction were recruited into the study. Laser speckle images were obtained from the abdominal and breast areas at different stages intraoperatively. Zonal perfusion was compared with the Holm classification and clinical observations. Twenty patients scheduled to undergo free flap breast reconstruction were recruited (23 reconstructed breasts) (mean age, 50 years; range, 32 to 68 years). Flap zonal perfusion was 238 (187 to 313), 222 (120 to 265), 206 (120 to 265), and 125 (102 to 220) perfusion units for zones I, II, III, and IV, respectively (analysis of variance, p < 0.0001). Zonal area with perfusion below an arbitrary perfusion threshold were 20 (0.3 to 75), 41 (3 to 99), 49 (9 to 97), and 99 (25 to 100) percent, respectively (analysis of variance, p < 0.0001). One example is presented to illustrate potential intraoperative uses for laser speckle imaging. This study shows that laser speckle imaging is a feasible, noninvasive technique for intraoperative mapping of tissue perfusion during free flap breast reconstruction. Zonal tissue perfusion was reduced across the Holm classification. Observations indicated the potential for laser speckle imaging to provide additional information to augment surgical decision-making by detection of inadequate tissue perfusion. This highlights the opportunity for surgeons to consider additional aids for intraoperative tissue perfusion assessment to help reduce perfusion-related complications. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Diagnostic, IV.

Provider perspectives on demand creation for maternal vaccines in Kenya.

Background . Expansion of maternal immunization, which offers some of the most effective protection against morbidity and mortality in pregnant women and neonates, requires broad acceptance by healthcare providers and their patients. We aimed to describe issues surrounding acceptance and demand creation for maternal vaccines in Kenya from a provider perspective. Methods . Nurses and clinical officers were recruited for semi-structured interviews covering resources for vaccine delivery, patient education, knowledge and attitudes surrounding maternal vaccines, and opportunities for demand creation for new vaccines. Interviews were conducted in English and Swahili, transcribed verbatim from audio recordings, and analyzed using codes developed from interview guide questions and emergent themes. Results . Providers expressed favorable attitudes about currently available maternal immunizations and introduction of additional vaccines, viewing themselves as primarily responsible for vaccine promotion and patient education.  The importance of educational resources for both patients and providers to maintain high levels of maternal immunization coverage was a common theme. Most identified barriers to vaccine acceptance and delivery were cultural and systematic in nature. Suggestions for improvement included improved patient and provider education, including material resources, and community engagement through religious and cultural leaders. Conclusions . The distribution of standardized, evidence-based print materials for patient education may reduce provider overwork and facilitate in-clinic efforts to inform women about maternal vaccines. Continuing education for providers should address communication surrounding current vaccines and those under consideration for introduction into routine schedules. Engagement of religious and community leaders, as well as male decision-makers in the household, will enhance future acceptance of maternal vaccines.

Interventions for improving modifiable risk factor control in the secondary prevention of stroke.

BACKGROUND: People with stroke or transient ischaemic attack (TIA) are at increased risk of future stroke and other cardiovascular events. Stroke services need to be configured to maximise the adoption of evidence-based strategies for secondary stroke prevention. Smoking-related interventions were examined in a separate review so were not considered in this review. This is an update of our 2014 review. OBJECTIVES: To assess the effects of stroke service interventions for implementing secondary stroke prevention strategies on modifiable risk factor control, including patient adherence to prescribed medications, and the occurrence of secondary cardiovascular events. SEARCH METHODS: We searched the Cochrane Stroke Group Trials Register (April 2017), the Cochrane Effective Practice and Organisation of Care Group Trials Register (April 2017), CENTRAL (the Cochrane Library 2017, issue 3), MEDLINE (1950 to April 2017), Embase (1981 to April 2017) and 10 additional databases including clinical trials registers. We located further studies by searching reference lists of articles and contacting authors of included studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that evaluated the effects of organisational or educational and behavioural interventions (compared with usual care) on modifiable risk factor control for secondary stroke prevention. DATA COLLECTION AND ANALYSIS: Four review authors selected studies for inclusion and independently extracted data. The quality of the evidence as 'high', 'moderate', 'low' or 'very low' according to the GRADE approach (GRADEpro GDT).Three review authors assessed the risk of bias for the included studies. We sought missing data from trialists.The results are presented in 'Summary of findings' tables. MAIN RESULTS: The updated review included 16 new studies involving 25,819 participants, resulting in a total of 42 studies including 33,840 participants. We used the Cochrane risk of bias tool and assessed three studies at high risk of bias; the remainder were considered to have a low risk of bias. We included 26 studies that predominantly evaluated organisational interventions and 16 that evaluated educational and behavioural interventions for participants. We pooled results where appropriate, although some clinical and methodological heterogeneity was present.Educational and behavioural interventions showed no clear differences on any of the review outcomes, which include mean systolic and diastolic blood pressure, mean body mass index, achievement of HbA1c target, lipid profile, mean HbA1c level, medication adherence, or recurrent cardiovascular events. There was moderate-quality evidence that organisational interventions resulted in improved blood pressure control, in particular an improvement in achieving target blood pressure (odds ratio (OR) 1.44, 95% confidence interval (CI) 1.09 to1.90; 13 studies; 23,631 participants). However, there were no significant changes in mean systolic blood pressure (mean difference (MD), -1.58 mmHg 95% CI -4.66 to 1.51; 16 studies; 17,490 participants) and mean diastolic blood pressure (MD -0.91 mmHg 95% CI -2.75 to 0.93; 14 studies; 17,178 participants). There were no significant changes in the remaining review outcomes. AUTHORS' CONCLUSIONS: We found that organisational interventions may be associated with an improvement in achieving blood pressure target but we did not find any clear evidence that these interventions improve other modifiable risk factors (lipid profile, HbA1c, medication adherence) or reduce the incidence of recurrent cardiovascular events. Interventions, including patient education alone, did not lead to improvements in modifiable risk factor control or the prevention of recurrent cardiovascular events.

The effects of feedback format, and egocentric & allocentric relative phase on coordination stability.

The stability of coordinated rhythmic movement is primarily affected by the required mean relative phase. In general, symmetrical coordination is more stable than asymmetrical coordination; however, there are two ways to define relative phase and the associated symmetries. The first is in an egocentric frame of reference, with symmetry defined relative to the sagittal plane down the midline of the body. The second is in an allocentric frame of reference, with symmetry defined in terms of the relative direction of motion. Experiments designed to separate these constraints have shown that both egocentric and allocentric constraints contribute to overall coordination stability, with the former typically showing larger effects. However, separating these constraints has meant comparing movements made either in different planes of motion, or by limbs in different postures. In addition, allocentric information about the coordination is either in the form of the actual limb motion, or a transformed, Lissajous feedback display. These factors limit both the comparisons that can be made and the interpretations of these comparisons. The current study examined the effects of egocentric relative phase, allocentric relative phase, and allocentric feedback format on coordination stability in a single task. We found that while all three independently contributed to stability, the egocentric constraint dominated. This supports previous work. We examine the evidence underpinning theoretical explanations for the egocentric constraint, and describe how it may reflect the haptic perception of relative phase.

MRTouch: Adding Touch Input to Head-Mounted Mixed Reality.

We present MRTouch, a novel multitouch input solution for head-mounted mixed reality systems. Our system enables users to reach out and directly manipulate virtual interfaces affixed to surfaces in their environment, as though they were touchscreens. Touch input offers precise, tactile and comfortable user input, and naturally complements existing popular modalities, such as voice and hand gesture. Our research prototype combines both depth and infrared camera streams together with real-time detection and tracking of surface planes to enable robust finger-tracking even when both the hand and head are in motion. Our technique is implemented on a commercial Microsoft HoloLens without requiring any additional hardware nor any user or environmental calibration. Through our performance evaluation, we demonstrate high input accuracy with an average positional error of 5.4 mm and 95% button size of 16 mm, across 17 participants, 2 surface orientations and 4 surface materials. Finally, we demonstrate the potential of our technique to enable on-world touch interactions through 5 example applications.

Imagined Steps: Mental Simulation of Coordinated Rhythmic Movements Effects on Pro-sociality.

Rhythmically coordinating with a partner can increase pro-sociality, but pro-sociality does not appear to change in proportion to coordination success, or particular classes of coordination. Pro-social benefits may have more to do with simply coordinating in a social context than the details of the actual coordination (Cross et al., 2016). This begs the question, how stripped down can a coordination task be and still affect pro-sociality? Would it be sufficient simply to imagine coordinating with others? Imagining a social interaction can lead to many of the same effects as actual interaction (Crisp and Turner, 2009). We report the first experiments to explore whether imagined coordination affects pro-sociality similarly to actual coordination. Across two experiments and over 450 participants, mentally simulated coordination is shown to promote some, but not all, of the pro-social consequences of actual coordination. Imagined coordination significantly increased group cohesion and de-individuation, but did not consistently affect cooperation.

Admission avoidance hospital at home.

BACKGROUND: Admission avoidance hospital at home provides active treatment by healthcare professionals in the patient's home for a condition that otherwise would require acute hospital inpatient care, and always for a limited time period. This is the third update of the original review. OBJECTIVES: To determine the effectiveness and cost of managing patients with admission avoidance hospital at home compared with inpatient hospital care. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, two other databases, and two trials registers on 2 March 2016. We checked the reference lists of eligible articles. We sought unpublished studies by contacting providers and researchers who were known to be involved in the field. SELECTION CRITERIA: Randomised controlled trials recruiting participants aged 18 years and over. Studies comparing admission avoidance hospital at home with acute hospital inpatient care. DATA COLLECTION AND ANALYSIS: We followed the standard methodological procedures expected by Cochrane and the Effective Practice and Organisation of Care (EPOC) Group. We performed meta-analysis for trials that compared similar interventions and reported comparable outcomes with sufficient data, requested individual patient data from trialists, and relied on published data when this was not available. We used the GRADE approach to assess the certainty of the body of evidence for the most important outcomes. MAIN RESULTS: We included 16 randomised controlled trials with a total of 1814 participants; three trials recruited participants with chronic obstructive pulmonary disease, two trials recruited participants recovering from a stroke, six trials recruited participants with an acute medical condition who were mainly elderly, and the remaining trials recruited participants with a mix of conditions. We assessed the majority of the included studies as at low risk of selection, detection, and attrition bias, and unclear for selective reporting and performance bias. Admission avoidance hospital at home probably makes little or no difference on mortality at six months' follow-up (risk ratio (RR) 0.77, 95% confidence interval (CI) 0.60 to 0.99; P = 0.04; I2 = 0%; 912 participants; moderate-certainty evidence), little or no difference on the likelihood of being transferred (or readmitted) to hospital (RR 0.98, 95% CI 0.77 to 1.23; P = 0.84; I2 = 28%; 834 participants; moderate-certainty evidence), and may reduce the likelihood of living in residential care at six months' follow-up (RR 0.35, 95% CI 0.22 to 0.57; P < 0.0001; I2 = 78%; 727 participants; low-certainty evidence). Satisfaction with healthcare received may be improved with admission avoidance hospital at home (646 participants, low-certainty evidence); few studies reported the effect on caregivers. When the costs of informal care were excluded, admission avoidance hospital at home may be less expensive than admission to an acute hospital ward (287 participants, low-certainty evidence); there was variation in the reduction of hospital length of stay, estimates ranged from a mean difference of -8.09 days (95% CI -14.34 to -1.85) in a trial recruiting older people with varied health problems, to a mean increase of 15.90 days (95% CI 8.10 to 23.70) in a study that recruited patients recovering from a stroke. AUTHORS' CONCLUSIONS: Admission avoidance hospital at home, with the option of transfer to hospital, may provide an effective alternative to inpatient care for a select group of elderly patients requiring hospital admission. However, the evidence is limited by the small randomised controlled trials included in the review, which adds a degree of imprecision to the results for the main outcomes.

Interventions to increase or decrease the length of primary care physicians' consultation.

BACKGROUND: Observational studies have shown differences in process and outcome between the consultations of primary care physicians whose average consultation lengths differ. These differences may be due to self selection. This is the first update of the original review. OBJECTIVES: To assess the effects of interventions to alter the length of primary care physicians' consultations. SEARCH METHODS: We searched the following electronic databases until 4 January 2016: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform (WHO ICTRP). SELECTION CRITERIA: Randomised controlled trials and non-randomised controlled trials of interventions to alter the length of primary care physicians' consultations. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed the risk of bias of included studies using agreed criteria and resolved disagreements by discussion. We attempted to contact authors of primary studies with missing data. Given the heterogeneity of studies, we did not conduct a meta-analysis. We assessed the certainty of the evidence for the most important outcomes using the GRADE approach and have presented the results in a narrative summary. MAIN RESULTS: Five studies met the inclusion criteria. All were conducted in the UK, and tested short-term changes in the consultation time allocated to each patient. Overall, our confidence in the results was very low; most studies had a high risk of bias, particularly due to non-random allocation of participants and the absence of data on participants' characteristics and small sample sizes. We are uncertain whether altering appointment length increases primary care consultation length, number of referrals and investigations, prescriptions, or patient satisfaction based on very low-certainty evidence. None of the studies reported on the effects of altering the length of consultation on resources used. AUTHORS' CONCLUSIONS: We did not find sufficient evidence to support or refute a policy of altering the lengths of primary care physicians' consultations. It is possible that these findings may change if high-quality trials are reported in the future. Further trials are needed that focus on health outcomes and cost-effectiveness.

A Dynamical Analysis of the Suitability of Prehistoric Spheroids from the Cave of Hearths as Thrown Projectiles.

Spheroids are ball-shaped stone objects found in African archaeological sites dating from 1.8 million years ago (Early Stone Age) to at least 70,000 years ago (Middle Stone Age). Spheroids are either fabricated or naturally shaped stones selected and transported to places of use making them one of the longest-used technologies on record. Most hypotheses about their use suggest they were percussive tools for shaping or grinding other materials. However, their size and spherical shape make them potentially useful as projectile weapons, a property that, uniquely, humans have been specialised to exploit for millions of years. Here we show (using simulations of projectile motions resulting from human throwing) that 81% of a sample of spheroids from the late Acheulean (Bed 3) at the Cave of Hearths, South Africa afford being thrown so as to inflict worthwhile damage to a medium-sized animal over distances up to 25 m. Most of the objects have weights that produce optimal levels of damage from throwing, rather than simply being as heavy as possible (as would suit other functions). Our results show that these objects were eminently suitable for throwing, and demonstrate how empirical research on behavioural tasks can inform and constrain our theories about prehistoric artefacts.

Using task dynamics to quantify the affordances of throwing for long distance and accuracy.

In 2 experiments, the current study explored how affordances structure throwing for long distance and accuracy. In Experiment 1, 10 expert throwers (from baseball, softball, and cricket) threw regulation tennis balls to hit a vertically oriented 4 ft × 4 ft target placed at each of 9 locations (3 distances × 3 heights). We measured their release parameters (angle, speed, and height) and showed that they scaled their throws in response to changes in the target's location. We then simulated the projectile motion of the ball and identified a continuous subspace of release parameters that produce hits to each target location. Each subspace describes the affordance of our target to be hit by a tennis ball moving in a projectile motion to the relevant location. The simulated affordance spaces showed how the release parameter combinations required for hits changed with changes in the target location. The experts tracked these changes in their performance and were successful in hitting the targets. We next tested unusual (horizontal) targets that generated correspondingly different affordance subspaces to determine whether the experts would track the affordance to generate successful hits. Do the experts perceive the affordance? They do. In Experiment 2, 5 cricketers threw to hit either vertically or horizontally oriented targets and successfully hit both, exhibiting release parameters located within the requisite affordance subspaces. We advocate a task dynamical approach to the study of affordances as properties of objects and events in the context of tasks as the future of research in this area. (PsycINFO Database Record