24 research outputs found
INFLUENCES ĂGOCENTRĂES SUR LA PERCEPTION DE L'ESPACE GĂOCENTRĂ - OBJECTIVATION AU TRAVERS DE L'ESTIMATION DU FRANCHISSEMENT D'OBSTACLES HAUTS
Perceiving space is a relevant task in determining our relationships with the environment. In behavioral neuroscience, investigating this spatial relationship can classically be explored with two theoretical approaches. The first one uses direct perception to describe the spatial relationships, involving affordances (i.e. the action ability naturally offer by the environment). The other one investigates the cognitive aspect of perception implying the use of spatial representation process. The later one traduces the existence of represented states which can be described through the interaction of different stable states called spatial reference frames. The present work investigates the contribution of the egocentric reference frame (body- related) on the perception of the geocentric space (earth-based). This was questioned through two research lines, (i) the origin of egocentric influence previously observed in darkness upon geocentric perception, (ii) the existence of the egocentric phenomenon in an enriched visual scene. To answer these questions, four experiments were conducted where the paradigm of passing under high obstacles was used. Overall, these results stress the powerful and complex aspect of the egocentric phenomenon observed upon geocentric perception. This work, discussed in term of interpenetrability between reference frames, provide an interesting support on the way how spatial reference frames are used in perceiving space.Percevoir son espace d'évolution est une activité déterminante dans l'élaboration des relations spatiales que nous tissons avec notre environnement. En neurosciences comportementales, l'étude de ces relations a généralement été abordée selon deux perspectives théoriques. L'une d'elle s'attache à décrire les relations au monde au travers des processus de perception directe impliquant notamment la notion d'affordances (i.e. de possibilités d'actions naturellement offertes par l'environnement) ; tandis que d'autres s'intéressent d'avantage aux aspects cognitifs de la perception avec la mise en place de processus de représentation spatiale. Cette derniÚre reflÚte notamment l'existence d'état(s) représenté(s) qu'il est possible de décrire à travers de la combinaison d'espaces stables appelés référentiels spatiaux. L'objectif de ce travail de thÚse vise à mieux comprendre la contribution du référentiel égocentré (i.e. corporel) dans la perception de l'espace géocentré (i.e. gravitaire). La question a notamment été abordée autour de deux axes de recherche interrogeant d'une part (i) l'origine de l'influence égocentrée préalablement observée dans le noir sur la perception géocentrée, et d'autre part (ii) la présence du phénomÚne égocentré dans un contexte visuel plus enrichi suite à l'ajout d'un flux optique. Pour ce faire quatre études centrées autour d'un paradigme d'estimation des possibilités de franchissement d'obstacles hauts ont été réalisées. Pris dans leur ensemble, les résultats expérimentaux soulignent le caractÚre particuliÚrement puissant et complexe du phénomÚne égocentré corporel observé sur la perception de l'espace gravitaire. Ces résultats, discutés en termes d'interpénétrabilité entre référentiels spatiaux offrent un support d'étude intéressant sur la maniÚre dont les référentiels sont utilisés dans les processus de représentation spatiale
INFLUENCES ĂGOCENTRĂES SUR LA PERCEPTION DE L'ESPACE GĂOCENTRĂ - OBJECTIVATION AU TRAVERS DE L'ESTIMATION DU FRANCHISSEMENT D'OBSTACLES HAUTS
Perceiving space is a relevant task in determining our relationships with the environment. In behavioral neuroscience, investigating this spatial relationship can classically be explored with two theoretical approaches. The first one uses direct perception to describe the spatial relationships, involving affordances (i.e. the action ability naturally offer by the environment). The other one investigates the cognitive aspect of perception implying the use of spatial representation process. The later one traduces the existence of represented states which can be described through the interaction of different stable states called spatial reference frames. The present work investigates the contribution of the egocentric reference frame (body- related) on the perception of the geocentric space (earth-based). This was questioned through two research lines, (i) the origin of egocentric influence previously observed in darkness upon geocentric perception, (ii) the existence of the egocentric phenomenon in an enriched visual scene. To answer these questions, four experiments were conducted where the paradigm of passing under high obstacles was used. Overall, these results stress the powerful and complex aspect of the egocentric phenomenon observed upon geocentric perception. This work, discussed in term of interpenetrability between reference frames, provide an interesting support on the way how spatial reference frames are used in perceiving space.Percevoir son espace d'évolution est une activité déterminante dans l'élaboration des relations spatiales que nous tissons avec notre environnement. En neurosciences comportementales, l'étude de ces relations a généralement été abordée selon deux perspectives théoriques. L'une d'elle s'attache à décrire les relations au monde au travers des processus de perception directe impliquant notamment la notion d'affordances (i.e. de possibilités d'actions naturellement offertes par l'environnement) ; tandis que d'autres s'intéressent d'avantage aux aspects cognitifs de la perception avec la mise en place de processus de représentation spatiale. Cette derniÚre reflÚte notamment l'existence d'état(s) représenté(s) qu'il est possible de décrire à travers de la combinaison d'espaces stables appelés référentiels spatiaux. L'objectif de ce travail de thÚse vise à mieux comprendre la contribution du référentiel égocentré (i.e. corporel) dans la perception de l'espace géocentré (i.e. gravitaire). La question a notamment été abordée autour de deux axes de recherche interrogeant d'une part (i) l'origine de l'influence égocentrée préalablement observée dans le noir sur la perception géocentrée, et d'autre part (ii) la présence du phénomÚne égocentré dans un contexte visuel plus enrichi suite à l'ajout d'un flux optique. Pour ce faire quatre études centrées autour d'un paradigme d'estimation des possibilités de franchissement d'obstacles hauts ont été réalisées. Pris dans leur ensemble, les résultats expérimentaux soulignent le caractÚre particuliÚrement puissant et complexe du phénomÚne égocentré corporel observé sur la perception de l'espace gravitaire. Ces résultats, discutés en termes d'interpénétrabilité entre référentiels spatiaux offrent un support d'étude intéressant sur la maniÚre dont les référentiels sont utilisés dans les processus de représentation spatiale
Egocentric influence on geocantric spatial perception : estimating the possibility of passing under high obstacles
Percevoir son espace dâĂ©volution est une activitĂ© dĂ©terminante dans lâĂ©laboration des relations spatiales que nous tissons avec notre environnement. En neurosciences comportementales, lâĂ©tude de ces relations a gĂ©nĂ©ralement Ă©tĂ© abordĂ©e selon deux perspectives thĂ©oriques. Lâune dâelle sâattache Ă dĂ©crire les relations au monde au travers des processus de perception directe impliquant notamment la notion dâaffordances (i.e. de possibilitĂ©s dâactions naturellement offertes par lâenvironnement) ; tandis que dâautres sâintĂ©ressent dâavantage aux aspects cognitifs de la perception avec la mise en place de processus de reprĂ©sentation spatiale. Cette derniĂšre reflĂšte notamment lâexistence dâĂ©tat(s) reprĂ©sentĂ©(s) quâil est possible de dĂ©crire Ă travers de la combinaison dâespaces stables appelĂ©s rĂ©fĂ©rentiels spatiaux. Lâobjectif de ce travail de thĂšse vise Ă mieux comprendre la contribution du rĂ©fĂ©rentiel Ă©gocentrĂ© (i.e. corporel) dans la perception de lâespace gĂ©ocentrĂ© (i.e. gravitaire). La question a notamment Ă©tĂ© abordĂ©e autour de deux axes de recherche interrogeant dâune part (i) lâorigine de lâinfluence Ă©gocentrĂ©e prĂ©alablement observĂ©e dans le noir sur la perception gĂ©ocentrĂ©e, et dâautre part (ii) la prĂ©sence du phĂ©nomĂšne Ă©gocentrĂ© dans un contexte visuel plus enrichi suite Ă lâajout dâun flux optique. Pour ce faire quatre Ă©tudes centrĂ©es autour dâun paradigme dâestimation des possibilitĂ©s de franchissement dâobstacles hauts ont Ă©tĂ© rĂ©alisĂ©es. Pris dans leur ensemble, les rĂ©sultats expĂ©rimentaux soulignent le caractĂšre particuliĂšrement puissant et complexe du phĂ©nomĂšne Ă©gocentrĂ© corporel observĂ© sur la perception de lâespace gravitaire. Ces rĂ©sultats, discutĂ©s en termes dâinterpĂ©nĂ©trabilitĂ© entre rĂ©fĂ©rentiels spatiaux offrent un support dâĂ©tude intĂ©ressant sur la maniĂšre dont les rĂ©fĂ©rentiels sont utilisĂ©s dans les processus de reprĂ©sentation spatiale.Perceiving space is a relevant task in determining our relationships with the environment. In behavioral neuroscience, investigating this spatial relationship can classically be explored with two theoretical approaches. The first one uses direct perception to describe the spatial relationships, involving affordances (i.e. the action ability naturally offer by the environment). The other one investigates the cognitive aspect of perception implying the use of spatial representation process. The later one traduces the existence of represented states which can be described through the interaction of different stable states called spatial reference frames. The present work investigates the contribution of the egocentric reference frame (body-related) on the perception of the geocentric space (earth-based). This was questioned through two research lines, (i) the origin of egocentric influence previously observed in darkness upon geocentric perception, (ii) the existence of the egocentric phenomenon in an enriched visual scene. To answer these questions, four experiments were conducted where the paradigm of passing under high obstacles was used. Overall, these results stress the powerful and complex aspect of the egocentric phenomenon observed upon geocentric perception. This work, discussed in term of interpenetrability between reference frames, provide an interesting support on the way how spatial reference frames are used in perceiving space
INFLUENCES EÌGOCENTREÌES SUR LA PERCEPTION DE L'ESPACE GEÌOCENTREÌ - OBJECTIVATION AU TRAVERS DE L'ESTIMATION DU FRANCHISSEMENT D'OBSTACLES HAUTS
Perceiving space is a relevant task in determining our relationships with the environment. In behavioral neuroscience, investigating this spatial relationship can classically be explored with two theoretical approaches. The first one uses direct perception to describe the spatial relationships, involving affordances (i.e. the action ability naturally offer by the environment). The other one investigates the cognitive aspect of perception implying the use of spatial representation process. The later one traduces the existence of represented states which can be described through the interaction of different stable states called spatial reference frames. The present work investigates the contribution of the egocentric reference frame (body- related) on the perception of the geocentric space (earth-based). This was questioned through two research lines, (i) the origin of egocentric influence previously observed in darkness upon geocentric perception, (ii) the existence of the egocentric phenomenon in an enriched visual scene. To answer these questions, four experiments were conducted where the paradigm of passing under high obstacles was used. Overall, these results stress the powerful and complex aspect of the egocentric phenomenon observed upon geocentric perception. This work, discussed in term of interpenetrability between reference frames, provide an interesting support on the way how spatial reference frames are used in perceiving space.Percevoir son espace d'eÌvolution est une activiteÌ deÌterminante dans l'eÌlaboration des relations spatiales que nous tissons avec notre environnement. En neurosciences comportementales, l'eÌtude de ces relations a geÌneÌralement eÌteÌ abordeÌe selon deux perspectives theÌoriques. L'une d'elle s'attache aÌ deÌcrire les relations au monde au travers des processus de perception directe impliquant notamment la notion d'affordances (i.e. de possibiliteÌs d'actions naturellement offertes par l'environnement) ; tandis que d'autres s'inteÌressent d'avantage aux aspects cognitifs de la perception avec la mise en place de processus de repreÌsentation spatiale. Cette dernieÌre refleÌte notamment l'existence d'eÌtat(s) repreÌsenteÌ(s) qu'il est possible de deÌcrire aÌ travers de la combinaison d'espaces stables appeleÌs reÌfeÌrentiels spatiaux. L'objectif de ce travail de theÌse vise aÌ mieux comprendre la contribution du reÌfeÌrentiel eÌgocentreÌ (i.e. corporel) dans la perception de l'espace geÌocentreÌ (i.e. gravitaire). La question a notamment eÌteÌ abordeÌe autour de deux axes de recherche interrogeant d'une part (i) l'origine de l'influence eÌgocentreÌe preÌalablement observeÌe dans le noir sur la perception geÌocentreÌe, et d'autre part (ii) la preÌsence du pheÌnomeÌne eÌgocentreÌ dans un contexte visuel plus enrichi suite aÌ l'ajout d'un flux optique. Pour ce faire quatre eÌtudes centreÌes autour d'un paradigme d'estimation des possibiliteÌs de franchissement d'obstacles hauts ont eÌteÌ reÌaliseÌes. Pris dans leur ensemble, les reÌsultats expeÌrimentaux soulignent le caracteÌre particulieÌrement puissant et complexe du pheÌnomeÌne eÌgocentreÌ corporel observeÌ sur la perception de l'espace gravitaire. Ces reÌsultats, discuteÌs en termes d'interpeÌneÌtrabiliteÌ entre reÌfeÌrentiels spatiaux offrent un support d'eÌtude inteÌressant sur la manieÌre dont les reÌfeÌrentiels sont utiliseÌs dans les processus de repreÌsentation spatiale
Perception of affordances during long-term exposure to weightlessness in the International Space station
Publisher Copyright: © 2015, Marta Olivetti Belardinelli and Springer-Verlag Berlin Heidelberg.On Earth, visual eye height (VEH)âthe distance from the observerâs line of gaze to the ground in the visual sceneâconstitutes an effective cue in perceiving affordance such as the passability through apertures, based on the assumption that oneâs feet are on the ground. In the present study, we questioned whether an observer continues to use VEH to estimate the width of apertures during long-term exposure to weightlessness, where contact with the floor is not required. Ten astronauts were tested in preflight, inflight in the International Space Station, and postflight sessions. They were asked to adjust the opening of a virtual doorway displayed on a laptop device until it was perceived to be just wide enough to pass through (i.e., the critical aperture). We manipulated VEH by raising and lowering the level of the floor in the visual scene. We observed an effect of VEH manipulation on the critical aperture. When VEH decreased, the critical aperture decreased too, suggesting that widths relative to the body were perceived to be larger when VEH was smaller. There was no overall significant session effect, but the analysis of between-subjects variability revealed two participant profile groups. The effect of weightlessness was different for these two groups even though the VEH strategy remained operational during spaceflight. This study shows that the VEH strategy appears to be very robust and can be used, if necessary, in inappropriate circumstances such as free-floating, perhaps promoted by the nature of the visual scene.Aurore Bourrelly was supported by a postdoctoral research fellowship from the CNES. The authors are grateful to the CNES, ESA, and the CNRS for funding and many people at CNES/CADMOS, ESA, NASA, and Roscosmos who made this study possible.Peer reviewe
Pitch body orientation influences the perception of self-motion direction induced by optic flow
International audienceWe studied the effect of static pitch body tilts on the perception of self-motion direction induced by a visual stimulus. Subjects were seated in front of a screen on which was projected a 3D cluster of moving dots visually simulating a forward motion of the observer with upward or downward directional biases (relative to a true earth horizontal direction). The subjects were tilted at various angles relative to gravity and were asked to estimate the direction of the perceived motion (nose-up, as during take-off or nose-down, as during landing). The data showed that body orientation proportionally affected the amount of error in the reported perceived direction (by 40% of body tilt magnitude in a range of +/- 20 degrees) and these errors were systematically recorded in the direction of body tilt. As a consequence, a same visual stimulus was differently interpreted depending on body orientation. While the subjects were required to perform the task in a geocentric reference frame (i.e., relative to a gravity-related direction), they were obviously influenced by egocentric references. These results suggest that the perception of self-motion is not elaborated within an exclusive reference frame (either egocentric or geocentric) but rather results from the combined influence of both. (C) 2010 Elsevier Ireland Ltd. All rights reserved
To pass or not to pass: More a question of body orientation than visual cues
International audienceThis study investigated the influence of pitch body tilt on judging the possibility of passing under high obstacles in the presence of an illusory horizontal self-motion. Seated subjects tilted at various body orientations were asked to estimate the possibility of passing under a projected bar (i.e., a parking barrier), while imagining a forward whole-body displacement normal to gravity. This task was performed under two visual conditions, providing either no visual surroundings or a translational horizontal optic flow that stopped just before the barrier appeared. The results showed a main overestimation of the possibility of passing under the bar in both cases and most importantly revealed a strong influence of body orientation despite the visual specification of horizontal self-motion by optic flow (i.e., both visual conditions yielded a comparable body tilt effect). Specifically, the subjective passability was proportionally deviated towards the body tilt by 46% of its magnitude when facing a horizontal optic flow and 43% without visual surroundings. This suggests that the egocentric attraction exerted by body tilt when referring the subjective passability to horizontal self-motion still persists even when anchoring horizontally related visual cues are displayed. These findings are discussed in terms of interaction between spatial references. The link between the reliability of available sensory inputs and the weight attributed to each reference is also addressed
Influence of gaze elevation on estimating the possibility of passing under high obstacles during body tilt
International audienceWe investigated the influence of gaze elevation on judging the possibility of passing under high obstacles during pitch body tilts, while stationary, in absence of allocentric cues. Specifically, we aimed at studying the influence of egocentric references upon geocentric judgements. Seated subjects, orientated at various body orientations, were asked to perceptually estimate the possibility of passing under a projected horizontal line while keeping their gaze on a fixation target and imagining a horizontal body displacement. The results showed a global overestimation of the possibility of passing under the line, and confirmed the influence of body orientation reported by Bringoux et al. (Exp Brain Res 185(4):673-680, 2008). More strikingly, a linear influence of gaze elevation was found on perceptual estimates. Precisely, downward eye elevation yielded increased overestimations, and conversely upward gaze elevation yielded decreased overestimations. Furthermore, body and gaze orientation effects were independent and combined additively to yield a global egocentric influence with a weight of 45 and 54%, respectively. Overall, our data suggest that multiple egocentric references can jointly affect the estimated possibility of passing under high obstacles. These results are discussed in terms of ``interpenetrability'' between geocentric and egocentric reference frames and clearly demonstrate that gaze elevation is involved, as body orientation, in geocentric spatial localization
How do healthy older pedestrians walk when they cross the street?
International audienc
Initiation of forward gait with lateral occurrence of emotional stimuli: general findings and relevance for pedestrians crossing roads
International audienceWith reference to theoretical models regarding links between emotions and actions, the present study examined whether the lateral occurrence of an emotional stimulus influences spatial and temporal parameters of gait initiation in 18 younger and 18 older healthy adults. In order to simulate road-crossing hazard for pedestrians, slides of approaching cars were used and they were presented in counterbalanced order with threatening slides from the International Affective Picture System (IAPS) and control slides of safe walking areas. Each slide was presented on the left side of the participant once the first step was initiated. The results evidenced medio-lateral shifts to the left for the first step (right foot) and to the right for the second step (left foot). These shifts were both modulated by the slide contents in such a way that the resulting distance between the screen and the foot (right or left) was larger with the IAPS and traffic slides than with the control slides. The slides did not affect the base of support, step length, step velocity and time of double support. Advancing age influenced the subjective impact of the slides and gait characteristics, but did not modulate medio-lateral shifts. The data extend evidence of fast, emotional modulation of stepping, with theoretical and applied consequences