943 resultados para end-state comfort


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Over the last decade, the end-state comfort effect (e.g., Rosenbaum et al., 2006) has received a considerable amount of attention. However, some of the underlying mechanisms are still to be investigated, amongst others, how sequential planning affects end-state comfort and how this effect develops over learning. In a two-step sequencing task, e.g., postural comfort can be planned on the intermediate position (next state) or on the actual end position (final state). It might be hypothesized that, in initial acquisition, next state’s comfort is crucial for action planning but that, in the course of learning, final state’s comfort is taken more and more into account. To test this hypothesis, a variant of Rosenbaum’s vertical stick transportation task was used. Participants (N = 16, right-handed) received extensive practice on a two-step transportation task (10,000 trials over 12 sessions). From the initial position on the middle stair of a staircase in front of the participant, the stick had to be transported either 20 cm upwards and then 40 cm downwards or 20 cm downwards and then 40 cm upwards (N = 8 per subgroup). Participants were supposed to produce fluid movements without changing grasp. In the pre- and posttest, participants were tested on both two-step sequencing tasks as well as on 20 cm single-step upwards and downwards movements (10 trials per condition). For the test trials, grasp height was calculated kinematographically. In the pretest, large end/next/final-state comfort effects for single-step transportation tasks and large next-state comfort effects for sequenced tasks were found. However, no change in grasp height from pre- to posttest could be revealed. Results show that, in vertical stick transportation sequences, the final state is not taken into account when planning grasp height. Instead, action planning seems to be solely based on aspects of the next action goal that is to be reached.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Recent research with several species of nonhuman primates suggests sophisticated motor-planning abilities observed in human adults may be ubiquitous among primates. However, there is considerable variability in the extent to which these abilities are expressed across primate species. In the present experiment, we explore whether the variability in the expression of anticipatory motor-planning abilities may be attributed to cognitive differences (such as tool use abilities) or whether they may be due to the consequences of morphological differences (such as being able to deploy a precision grasp). We compared two species of New World monkeys that differ in their tool use abilities and manual dexterity: squirrel monkeys, Saimiri sciureus (less dexterous with little evidence for tool use) and tufted capuchins, Sapajus apella (more dexterous and known tool users). The monkeys were presented with baited cups in an untrained food extraction task. Consistent with the morphological constraint hypothesis, squirrel monkeys frequently showed second-order motor planning by inverting their grasp when picking up an inverted cup, while capuchins frequently deployed canonical upright grasping postures. Findings suggest that the lack of ability for precision grasping may elicit more consistent second-order motor planning, as the squirrel monkeys (and other species that have shown a high rate of second-order planning) have fewer means of compensating for inefficient initial postures. Thus, the interface between morphology and motor planning likely represents an important factor for understanding both the ontogenetic and phylogenetic origins of sophisticated motor-planning abilities.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Recent research with several species of nonhuman primates suggests sophisticated motor-planning abilities observed in human adults may be ubiquitous among primates. However, there is considerable variability in the extent to which these abilities are expressed across primate species. In the present experiment, we explore whether the variability in the expression of anticipatory motor-planning abilities may be attributed to cognitive differences (such as tool use abilities) or whether they may be due to the consequences of morphological differences (such as being able to deploy a precision grasp). We compared two species of New World monkeys that differ in their tool use abilities and manual dexterity: squirrel monkeys, Saimiri sciureus (less dexterous with little evidence for tool use) and tufted capuchins, Sapajus apella (more dexterous and known tool users). The monkeys were presented with baited cups in an untrained food extraction task. Consistent with the morphological constraint hypothesis, squirrel monkeys frequently showed second-order motor planning by inverting their grasp when picking up an inverted cup, while capuchins frequently deployed canonical upright grasping postures. Findings suggest that the lack of ability for precision grasping may elicit more consistent second-order motor planning, as the squirrel monkeys (and other species that have shown a high rate of second-order planning) have fewer means of compensating for inefficient initial postures. Thus, the interface between morphology and motor planning likely represents an important factor for understanding both the ontogenetic and phylogenetic origins of sophisticated motor-planning abilities. (C) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Multiple recent studies provide evidence that both human and nonhuman primates possess motor planning abilities. I tested for the demonstration of motor planning in two previously untested primate species through two experiments. In the first experiment, I compared the extent to which squirrel monkeys (Saimiri sciureus) and brown capuchins (Cebus apella) plan their movements in a grasping task. Individuals were presented with an inverted cup that required being turned and held upright in order to extract a food reward from the inside of the cup. This task was most efficiently solved by using an initially awkward inverted grasp that affords a comfortable hand and arm orientation at the end of the movement (known as end-state comfort). While certain individuals from both species exhibited end-state comfort, many of the capuchins never demonstrated this type of motor planning. Furthermore, the squirrel monkeys used the efficient grasp significantly more than the capuchins. In the second experiment, I presented the capuchins with another grasping task to test if they would express motor planning abilities in a different context. Here, the capuchins were offered a dowel that was baited on either the left or right end. A radial grasp with the thumb pointing towards the baited end was considered to be the most efficient grasp because it afforded a comfortable final position. The capuchins switched hands and used an overhand radial grasp on the dowel significantly more often than not, thus demonstrating motor planning in this task. The grasps typically utilized by these two closely related species differ considerably in that capuchins are capable of exercising precision grips, whereas squirrel monkeys are limited to whole-handed power grips. Moreover, unlike capuchins, squirrel monkeys are not particularly dexterous nor are they capable of precise manipulative actions. It is therefore more beneficial for squirrel monkeys to plan their movements efficiently because they are less capable of compensating for inappropriate initial grasps. Due to the appreciable variability in the expression of motor planning skills across species, I proposed that morphological constraints might explain the observed discrepancies in movement planning among different primate species.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

We prove the existence of novel, shock-fronted travelling wave solutions to a model of wound healing angiogenesis studied in Pettet et al (2000 IMA J. Math. App. Med. 17 395–413) assuming two conjectures hold. In the previous work, the authors showed that for certain parameter values, a heteroclinic orbit in the phase plane representing a smooth travelling wave solution exists. However, upon varying one of the parameters, the heteroclinic orbit was destroyed, or rather cut-off, by a wall of singularities in the phase plane. As a result, they concluded that under this parameter regime no travelling wave solutions existed. Using techniques from geometric singular perturbation theory and canard theory, we show that a travelling wave solution actually still exists for this parameter regime. We construct a heteroclinic orbit passing through the wall of singularities via a folded saddle canard point onto a repelling slow manifold. The orbit leaves this manifold via the fast dynamics and lands on the attracting slow manifold, finally connecting to its end state. This new travelling wave is no longer smooth but exhibits a sharp front or shock. Finally, we identify regions in parameter space where we expect that similar solutions exist. Moreover, we discuss the possibility of more exotic solutions.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Strategic planning can be an arduous and complex task; and, once a plan has been devised, it is often quite a challenge to effectively communicate the principal missions and key priorities to the array of different stakeholders. The communication challenge can be addressed through the application of a clearly and concisely designed visualisation of the strategic plan - to that end, this paper proposes the use of a roadmapping framework to structure a visual canvas. The canvas provides a template in the form of a single composite visual output that essentially allows a 'plan-on-a-page' to be generated. Such a visual representation provides a high-level depiction of the future context, end-state capabilities and the system-wide transitions needed to realise the strategic vision. To demonstrate this approach, an illustrative case study based on the Australian Government's Defence White Paper and the Royal Australian Navy's fleet plan will be presented. The visual plan plots the in-service upgrades for addressing the capability shortfalls and gaps in the Navy's fleet as it transitions from its current configuration to its future end-state vision. It also provides a visualisation of project timings in terms of the decision gates (approval, service release) and specific phases (proposal, contract, delivery) together with how these projects are rated against the key performance indicators relating to the technology acquisition process and associated management activities. © 2013 Taylor & Francis.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Data are reported demonstrating the potential role of microscale morphologies, induced by endolithic lichen communities, specifically Verrucaria baldensis, in the initiation and development of mesoscale solution basin formation on limestone in the Burren, Co. Clare. A biophysical model is proposed outlining the different microscale stages leading to solution basin initiation with a progression from initial lichen colonisation and growth, associated biopitting followed by biopit coalescence to form biotroughs, their subsequent enlargement and eventual incipient solution basin formation. This model provides one explanation for solution basin development as this end state may also be achieved through simple solutional means without biological input. The complexity of interactions at the rock / lichen interface are identified with emphasis on the spatial and temporal variability of these underlining the point that, as with macro-topographies at the landscape scale, rock surface micro-topographies also reflect historical weathering legacies.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

This paper explores the prospects and challenges of achieving human security through United Nations (UN) human rights law. The paper does not aim to pronounce definitively on the achievement of human security by way of UN human rights law that is, to assess the achievement of human security per se 'as a future end state'. Rather the focus of the paper is firmly placed on the capacity of UN human rights law to achieve human security. The paper departs from the premise that if human rights define human security, international human rights law and UN human rights law in particular should have something to say about the achievement of human security.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Personality traits and personal values are two important domains of individual differences. Traits are enduring and distinguishable patterns of behaviour whereas values are societally taught, stable, individual preferences that guide behaviour in order to reach a specific end state. The purpose of the present study was to investigate the relations between self and peer report within the domains of personality traits and values, to examine the correlations between values and traits, and to explore the amount of incremental validity of traits and values in predicting behaviour. Two hundred and fiftytwo men and women from a university setting completed self and peer reports on three questionnaires. In order to assess personality traits, the HEXACO-PI (Lee & Ashton, 2004) was used to identify levels of 6 major dimensions of personality in participants. To assess values, the Schwartz Value Survey (Schwartz, 1992) was used to identify the importance each participant placed on each of Schwartz's 10 value types. To measure behaviour, a Behavior Scale, created by Bardi and Schwartz (2003), consisting of items designed to measure the frequency of value-expressive behaviour was used. As expected, correlations between self and peer reports for the personality scales were high indicating that personality traits are easily observable to other people. Correlations between self and peer reports for the values and behaviour scales were only moderate, suggesting that some goals, and behaviours expressive of those goals, may not always be observable to others. Consistent with previous research, there were many strong correlations between traits and values. In addition to the similarities with past research, the present study found that the personality factor Honesty-Humility was correlated strongly with values scales (with five correlations exceeding .25). In the prediction of behaviour, it was found that both personahty and values were able to account for significant and similar amounts of variance. Personality outpredicted values for some behaviours, but the opposite was true of other behaviours. Each domain provided incremental validity beyond the other domain. The impUcations for these findings, along with limitations, and possibilities for future research are also discussed.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The objective of the present work was to study the control of the dynamics of diatomic heteronuclear molecules interacting with electric fields created by lasers. Specifically in this work, the molecular photoassociation phenomenon will be analyzed. At this phenomenon, the atom's relative movement is described by a particle that moves in a morse potential well under the influence of an external time dependant force related to the external field. Based on the optimum control theory (OCT), it is presented at the present work laser pulses that alternate a given initial molecular state to a desirable end state, wich in this work was represented by the minimization of a cost functional that indicates how close. To do so, a computational sistem know as Genetic Algorithm (GA) was developed that can be characterizes as an extremelly eficient technique capable of scanning the solutions space and find results close to the optimum solutions

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The motor system can no longer be considered as a mere passive executive system of motor commands generated elsewhere in the brain. On the contrary, it is deeply involved in perceptual and cognitive functions and acts as an “anticipation device”. The present thesis investigates the anticipatory motor mechanisms occurring in two particular instances: i) when processing sensory events occurring within the peripersonal space (PPS); and ii) when perceiving and predicting others’actions. The first study provides evidence that PPS representation in humans modulates neural activity within the motor system, while the second demonstrates that the motor mapping of sensory events occurring within the PPS critically relies on the activity of the premotor cortex. The third study provides direct evidence that the anticipatory motor simulation of others’ actions critically relies on the activity of the anterior node of the action observation network (AON), namely the inferior frontal cortex (IFC). The fourth study, sheds light on the pivotal role of the left IFC in predicting the future end state of observed right-hand actions. Finally, the fifth study examines how the ability to predict others’ actions could be influenced by a reduction of sensorimotor experience due to the traumatic or congenital loss of a limb. Overall, the present work provides new insights on: i) the anticipatory mechanisms of the basic reactivity of the motor system when processing sensory events occurring within the PPS, and the same anticipatory motor mechanisms when perceiving others’ implied actions; ii) the functional connectivity and plasticity of premotor-motor circuits both during the motor mapping of sensory events occurring within the PPS and when perceiving others’ actions; and iii) the anticipatory mechanisms related to others’ actions prediction.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Phylogenetic analyses of asymmetry variation offer a powerful tool for exploring the interplay between ontogeny and evolution because (i) conspicuous asymmetries exist in many higher metazoans with widely varying modes of development, (ii) patterns of bilateral variation within species may identify genetically and environmentally triggered asymmetries, and (iii) asymmetries arising at different times during development may be more sensitive to internal cytoplasmic inhomogeneities compared to external environmental stimuli. Using four broadly comparable asymmetry states (symmetry, antisymmetry, dextral, and sinistral), and two stages at which asymmetry appears developmentally (larval and postlarval), I evaluated relations between ontogenetic and phylogenetic patterns of asymmetry variation. Among 140 inferred phylogenetic transitions between asymmetry states, recorded from 11 classes in five phyla, directional asymmetry (dextral or sinistral) evolved directly from symmetrical ancestors proportionally more frequently among larval asymmetries. In contrast, antisymmetry, either as an end state or as a transitional stage preceding directional asymmetry, was confined primarily to postlarval asymmetries. The ontogenetic origin of asymmetry thus significantly influences its subsequent evolution. Furthermore, because antisymmetry typically signals an environmentally triggered asymmetry, the phylogenetic transition from antisymmetry to directional asymmetry suggests that many cases of laterally fixed asymmetries evolved via genetic assimilation.