The nature of body representations in perception and action
Accurate information about body structure and posture is fundamental for effective control of our actions. It is often assumed that healthy adults have accurate representations of their body. Although peoples abilities to visually recognize their own body size and shape are relatively good, the implicit spatial representation of their body is extremely distorted . For instance, peoples tactile size perception of their hand is much larger in width and shorter in length than the actual size of the hand .
The aim of my research is to understand the nature of spatial distortions of the body. In particular, I investigate the perceptual-cognitive components contributing to distortions of implicit representation of the human hand.
Figure 1. Images of the items used in the experiment. From left to right: hand, rake, post-it, box presented to the participant in upright (top row) and rotated (bottom row) orientation. The yellow and red lines on the items were not present during experimentation and have been drawn to illustrate the item-centric width and length dimensions used to calculate the aspect ratio of the item.
To examine whether previously observed distortions only occur with the human body, I investigated whether similar distortions are observable with non-body items such as objects (Rake, post-it block and CD case). The distortions of the implicit spatial representation of these items were assessed with a localization task (see figure 1.A). I also assessed the explicit visual bias in perception of each item in a template matching task. The comparison of the distortions of the localization task and the template matching task reveals whether implicit spatial distortions are owed to a bias in explicit visual perception.
Figure 2. Actual and estimated landmarks for the upright hand (left) and rake (right) averaged across 16 participants in the localization task. The filled circles indicate the mean location of actual landmarks (blue) and estimated landmarks (red).
Distortions in the localization task were found with both the hand and non-body items. No distortions were found in the visual template matching task. Interestingly the distortions measured on the objects in the localization task present a similar pattern of distortion to the one previously measured on the hand. This is especially the case of the rake who shares a similar structure to the human hand. Both the rake and the hand had slight overestimation of their width and an underestimation of their length. Moreover the distortions present on the rake were a significant predictor of the distortions measured on the human hand.
Overall, these results show that distortions of implicit spatial representations can be observed with body and non-body objects. These results have implications for theoretical accounts associating previously observed distortions with somatosensation: because localizing points on an object is unlikely to be aided by somatosensation, the assessed representations might reflect the contribution of other cognitive processes (e.g. visual spatial memory) to the distortion of the body model [3; 4].
1. Longo, M. R., & Haggard, P. (2010). An implicit body representation underlying human position sense. Proceedings of the National Academy of Sciences, 107(26), 1172711732. doi:10.1073/pnas.1003483107
2. Longo, M. R., & Haggard, P. (2011). Webers illusion and body shape: Anisotropy of tactile size perception on the hand. Journal of Experimental Psychology: Human Perception and Performance, 37(3), 720726. doi:10.1037/a0021921
3. Saulton A, de la Rosa S and Bülthoff H (August-2013): Implicit spatial representation of objects and hand size, 36th European Conference on Visual Perception (ECVP 2013), Bremen, Germany, Perception, 42(ECVP Abstract Supplement) 176.
4.Saulton A, Dodds T ,Bülthoff HH , and de la Rosa S.(2015). Objects exhibit body model like shape distortions. Experimental brain research (in press).
2013: Phd Student at the Max Planck Institute for biological Cybernetics;Social and Spatial Cognition Group.
2012-2013 : Internship in the Space and Body Perception group; EU-Vr-Hyperspace Project (supervision: Betty Mohler);
5-16 Sept. 2011: Barcelona Cognition, Brain and Technology summer school; Robotics and virtual systems; Pompeu Fabra University; Spain.
2009-2011: MSc in cognitive science with a major in experimental psychology; Cogmaster;Paris Descartes University Ecole Normale Supérieure (ENS) Ecole des Hautes Etudes en Sciences Sociales (EHESS)
2006-2009: BA in cognitive anthropology; Nice Sophia Antipolis University
2004-2006: 2 year degree (Deug) in physics with a major in astrophysics; Paris 11 university
2003-2004: High-school degree (scientific baccalaureat); major in physics and music
Sept.2011: 3rd prize best group project; Real-time visualization of a DAC-based robot brain activity. Pompeu Fabra University; Spain.
Scientific & work experience
2010-2011: Influence of optic flow on newborns stepping, Laboratoire de Psychologie de la Perception, Paris; Tutor: Marianne Barbu-Roth
2009-2010: fMRI study of neural correlates associated to the feeling of doubt in patients with Obsessional-Compulsives Disorder (OCD), Behavior, Emotion & Basal Ganglia, INSERM, Paris; Tutors: Luc Mallet & Karim NDiaye
August-September 2009: Perception of numerical quantities in newborns, Laboratoire de Psychologie de la Perception, Paris; Tutor: Arlette Streri
June-July 2009: Study of moral judgments in young children, Jean Nicod Institute, Paris; Tutor: Nicolas Baumard
January-May 2009: Study of emotional contagion in street music, Nice; Tutor: Arnaud Alloy
June- August 2008: Study of a religious ritual Le kourbani des saints, Skyros Island (Greece)
2007-2008: Epidemiological representations associated to the controversial debate on Genetically Modified Organisms, France; Tutor: Joel Candau
Summer 2006: Measurement of the sun diameter with an helioscopic telescope; Pic du Midi Observatory; Tutor: Jean Pierre Rozelot
Summer 2005: Analyses of micrometeorites using transmission electron microscopy; CSNSM, Orsay; Tutors: Cecile Engrand & Jean Duprat
Summer 2004: Stratospheric and tropospheric temperatures analyses; Côte dAzur Observatory; Tutor: Jean Pierre Rozelot
Good experience in experimental design, data collection and analyses (behavioral studies with healthy and patient adults, infants; inter-cultural field work)
Good knowledge in programming (Unity C#; python; matlab)
Good knowledge in statistics analysis (excel, statistica, R studio)
French: native language
Jobs scientific animation for children (robotics, nature, basic physics); permanent member of an association in astronomy (observation/star-party animation/conferences); girl au Pair (Greece); Factory work (Dusseldorf-Germany); Waitress
Organizational Unit (Department, Group, Facility):
- Alumni of the Department Human Perception, Cognition & Action
- Alumni of the Group Perception & Action in Virtual Environments
- Alumni of the Group Recognition & Categorization
- Alumni of the Group Social & Spatial Cognition