Amplitude and direction errors in kinesthetic pointing

We investigated the accuracy with which, in the absence of vision, one can reach again a 2D target location that had been previously identified by a guided movement. A robotic arm guided the participant's hand to a target (locating motion) and away from it (homing motion). Then, the participant pointed freely toward the remembered target position. Two experiments manipulated separately the kinematics of the locating and homing motions. Some robot motions followed a straight path with the bell-shaped velocity profile that is typical of natural movements. Other motions followed curved paths, or had strong acceleration and deceleration peaks. Current motor theories of perception suggest that pointing should be more accurate when the homing and locating motion mimics natural movements. This expectation was not borne out by the results, because amplitude and direction errors were almost independent of the kinematics of the locating and homing phases. In both experiments, participants tended to overshoot the target positions along the lateral directions. In addition, pointing movements towards oblique targets were attracted by the closest diagonal (oblique effect). This error pattern was robust not only with respect to the manner in which participants located the target position (perceptual equivalence), but also with respect to the manner in which they executed the pointing movements (motor equivalence). Because of the similarity of the results with those of previous studies on visual pointing, it is argued that the observed error pattern is basically determined by the idiosyncratic properties of the mechanisms whereby space is represented internall

Neural bases of hand synergies

The human hand has so many degrees of freedom that it may seem impossible to control. A potential solution to this problem is "synergy control" which combines dimensionality reduction with great flexibility. With applicability to a wide range of tasks, this has become a very popular concept. In this review, we describe the evolution of the modern concept using studies of kinematic and force synergies in human hand control, neurophysiology of cortical and spinal neurons, and electromyographic (EMG) activity of hand muscles. We go beyond the often purely descriptive usage of synergy by reviewing the organization of the underlying neuronal circuitry in order to propose mechanistic explanations for various observed synergy phenomena. Finally, we propose a theoretical framework to reconcile important and still debated concepts such as the definitions of "fixed" vs. "flexible" synergies and mechanisms underlying the combination of synergies for hand control

The Visual Localization of the Centre of Triangles in Young Children and Adults

La notion de centre est ambiguë pour la plupart des formes géométriques. Pour étudier cette question, nous avons demandé à des enfants âgés de cinq ans et à des adultes de marquer le centre d'un triangle sur une feuille de papier. Les réponses des deux groupes étaient très similaires. Premièrement, les deux groupes tendaient à percevoir le centre du triangle rectangle à mi-distance entre le centre de masse et le centre du cercle inscrit. Deuxièmement, la position du centre du triangle équilatéral était déplacée en direction de la pointe opposée au côté horizontal. Ces résultats suggèrent que la localisation visuelle du  centre de triangles dépend de processus perceptifs de bas-niveau, déjà en place à l'âge de cinq ans.The ambiguity of the notion of centre for most shapes raises the question of whether children perceive the centre of a shape in the same place as adults. To answer this question, we asked five- year old children and adults to mark the centre of a triangle with a pen. The responses of children and adults were strikingly similar. First, the two groups perceived the centre of right triangles at mid-distance between the centre of mass and the centre of the inscribed circles. Second, the perceptual centre of the equilateral triangle was shifted toward the vertex that opposed the horizontal edge of the triangle for children and adults alike. These results suggest that the visual localization of the centre of triangles would depend on low-level sensori-motor processes that are in place since at least the age of five

MIE 2017: 1st international workshop on multimodal interaction for education (workshop summary)

The International Workshop on Multimodal Interaction for Education aims at investigating how multimodal interactive systems, firmly grounded on psychophysical, psychological, and pedagogical bases, can be designed, developed, and exploited for enhancing teaching and learning processes in different learning environments, with a special focus on children in the classroom. Whilst the usage of multisensory technologies in the education area is rapidly expanding, the need for solid scientific bases, design guidelines, and appropriate procedures for evaluation is emerging. Moreover, the introduction of multimodal interactive systems in the learning environment needs to develop at the same time suitable pedagogical paradigms. This workshop aims at bringing together researchers and practitioners from different disciplines, including pedagogy, psychology, psychophysics, and computer science - with a particular focus on human-computer interaction, affective computing, and social signal processing - to discuss such challenges under a multidisciplinary perspective. The workshop is partially supported by the EU-H2020-ICT Project weDRAW (http://www.wedraw.eu)

An instrumented manipulandum for human grasping studies

This work presents a novel haptic device to study human grasp, which integrates different technological solutions thus enabling, for the first time, to achieve: (i) a complete grasp characterization in terms of contact forces and moments; (ii) an estimation of contact point location for varying-orientation contact surfaces; (iii) a compensation of force/torque offsets and estimation of the mass and center of mass of the device, for different orientations and configurations in the workspace; (iv) different stiffness properties for the contact points, i.e. rigid, compliant non-deformable and compliant deformable, thus allowing to study the effects of cutaneous cues in multi-finger grasps. In addition, given the modularity of the architecture and the simple mechanism to attach/detach the contact modules, this structure can be easily modified in order to analyze different multi-finger grasp configurations. The effectiveness of this device was experimentally demonstrated and applications to neuroscientific studies and state of the art of devices for similar investigations are discussed in depth within the text

Enhancing Visual Exploration through Augmented Gaze:High Acceptance of Immersive Virtual Biking by Oldest Olds

The diffusion of virtual reality applications dedicated to aging urges us to appraise its acceptance by target populations, especially the oldest olds. We investigated whether immersive virtual biking, and specifically a visuomotor manipulation aimed at improving visual exploration (augmented gaze), was well accepted by elders living in assisted residences. Twenty participants (mean age 89.8 years, five males) performed three 9 min virtual biking sessions pedalling on a cycle ergometer while wearing a Head-Mounted Display which immersed them inside a 360-degree pre-recorded biking video. In the second and third sessions, the relationship between horizontal head rotation and contingent visual shift was experimentally manipulated (augmented gaze), the visual shift being twice (gain = 2.0) or thrice (gain = 3.0) the amount of head rotation. User experience, motion sickness and visual exploration were measured. We found (i) very high user experience ratings, regardless of the gain; (ii) no effect of gain on motion sickness; and (iii) increased visual exploration (slope = +46%) and decreased head rotation (slope = −18%) with augmented gaze. The improvement in visual exploration capacity, coupled with the lack of intolerance signs, suggests that augmented gaze can be a valuable tool to improve the “visual usability” of certain virtual reality applications for elders, including the oldest olds

The haptic perception of spatial orientations

This review examines the isotropy of the perception of spatial orientations in the haptic system. It shows the existence of an oblique effect (i.e., a better perception of vertical and horizontal orientations than oblique orientations) in a spatial plane intrinsic to the haptic system, determined by the gravitational cues and the cognitive resources and defined in a subjective frame of reference. Similar results are observed from infancy to adulthood. In 3D space, the haptic processing of orientations is also anisotropic and seems to use both egocentric and allocentric cues. Taken together, these results revealed that the haptic oblique effect occurs when the sensory motor traces associated with exploratory movement are represented more abstractly at a cognitive level

A gaze-addressing communication system using artificial neural networks

Severe motor disabilities can render a person almost completely incapable of communication. Nevertheless, in many cases, the sensory systems are intact and the eye movements are still under good control. In these cases, one can use a device such as the Brain Response Interface (BRI) to command a remote control (e.g. room temperature, bed position), a word-processor, a speech synthesizer, and so on