Gravity and observer's body orientation influence the visual perception of human body postures.

Since human behavior and perception have evolved within the Earth's gravitational field, humans possess an internal model of gravity. Although gravity is known to influence the visual perception of moving objects, the evidence is less clear concerning the visual perception of static objects. We investigated whether a visual judgment of the stability of human body postures (static postures of a human standing on a platform and tilted in the roll plane) may also be influenced by gravity and by the participant's orientation. Pictures of human body postures were presented in different orientations with respect to gravity and the participant's body. The participant's body was aligned to gravity (upright) or not (lying on one side). Participants performed stability judgments with respect to the platform, imagining that gravity operates in the direction indicated by the platform (that was or was not concordant with physical gravity). Such visual judgments were influenced by the picture's orientation with respect to physical gravity. When pictures were tilted by 90 degrees with respect to physical gravity, the human postures that were tilted toward physical gravity (down) were perceived as more unstable than similar postures tilted away from physical gravity (up). Stability judgments were also influenced by the picture's orientation with respect to the participant's body. This indicates that gravity and the participant's body position may influence the visual perception of static objects.

[1]  F. Lacquaniti,et al.  Does the brain model Newton's laws? , 2001, Nature Neuroscience.

[2]  L. Harris,et al.  Levels of Perception , 2013, Springer New York.

[3]  Laurence R Harris,et al.  Shape-from-Shading Depends on Visual, Gravitational, and Body-Orientation Cues , 2004, Perception.

[4]  J. V. Van Gisbergen,et al.  Properties of the internal representation of gravity inferred from spatial-direction and body-tilt estimates. , 2000, Journal of neurophysiology.

[5]  N. Troje,et al.  The Inversion Effect in Biological Motion Perception: Evidence for a “Life Detector”? , 2006, Current Biology.

[6]  E. Spelke,et al.  Perception and understanding of effects of gravity and inertia on object motion , 1999 .

[7]  S. Bouisset,et al.  Posture, dynamic stability, and voluntary movement , 2008, Neurophysiologie Clinique/Clinical Neurophysiology.

[8]  I. M. Harris,et al.  Anatomical limitations in mental transformations of body parts , 2005 .

[9]  I. Howard,et al.  Relative role of visual and non-visual cues in determining the direction of "up": experiments in the York tilted room facility. , 2003, Journal of vestibular research : equilibrium & orientation.

[10]  Nikolaus F Troje,et al.  Reference Frames for Orientation Anisotropies in Face Recognition and Biological-Motion Perception , 2003, Perception.

[11]  H. Mittelstaedt.  A new solution to the problem of the subjective vertical , 1983, Naturwissenschaften.

[12]  E S Spelke,et al.  Infants' sensitivity to effects of gravity on visible object motion. , 1992, Journal of experimental psychology. Human perception and performance.

[13]  J. Roll,et al.  Eye, head and skeletal muscle spindle feedback in the elaboration of body references. , 1989, Progress in brain research.

[14]  Marion Trousselard,et al.  Contribution of tactile and interoceptive cues to the perception of the direction of gravity. , 2004, Brain research. Cognitive brain research.

[15]  A M Bronstein,et al.  The Interaction of Otolith and Proprioceptive Information in the Perception of Verticality: The Effects of Labyrinthine and CNS Disease , 1999, Annals of the New York Academy of Sciences.

[16]  Timothy L. Hubbard,et al.  Target size and displacement along the axis of implied gravitational attraction : Effects of implied weight and evidence of representational gravity , 1997 .

[17]  F. Lacquaniti,et al.  Representation of Visual Gravitational Motion in the Human Vestibular Cortex , 2005, Science.

[18]  Dora E. Angelaki,et al.  Neurons compute internal models of the physical laws of motion , 2004, Nature.

[19]  Christophe Lopez,et al.  Changes of visual vertical perception: A long-term sign of unilateral and bilateral vestibular loss , 2007, Neuropsychologia.

[20]  Pierre Pica,et al.  Core knowledge of geometry in an Amazonian indigene group. , 2006, Science.

[21]  Horst Mittelstaedt,et al.  The role of the otoliths in the perception of the orientation of self and world to the vertical , 1991 .

[22]  Francesco Lacquaniti,et al.  Anticipating the effects of gravity when intercepting moving objects: differentiating up and down based on nonvisual cues. , 2005, Journal of neurophysiology.

[23]  Gilles Clément,et al.  Influence of the gravitational vertical on geometric visual illusions. , 2005, Acta astronautica.

[24]  O. Blanke,et al.  In X uence of galvanic vestibular stimulation on egocentric and object-based mental transformations , 2022 .

[25]  L. Snyder.  This way up: illusions and internal models in the vestibular system , 1999, Nature Neuroscience.

[26]  T. Hubbard.  Representational momentum and related displacements in spatial memory: A review of the findings , 2005, Psychonomic bulletin & review.

[27]  M Dieterich,et al.  Effects of galvanic vestibular stimulation on otolithic and semicircular canal eye movements and perceived vertical. , 1998, Electroencephalography and Clinical Neurophysiology.

[28]  L. Harris,et al.  The subjective visual vertical and the perceptual upright , 2006, Experimental Brain Research.

[29]  F. Mast,et al.  The Thatcher Illusion: Rotating the Viewer Instead of the Picture , 2007, Perception.

[30]  J. Lackner.  Some proprioceptive influences on the perceptual representation of body shape and orientation. , 1988, Brain : a journal of neurology.

[31]  D M Merfeld,et al.  Humans use internal models to estimate gravity and linear acceleration , 1999, Nature.

[32]  James Park,et al.  The Brain's Sense of Movement , 2003, The Yale Journal of Biology and Medicine.

[33]  J. Freyd,et al.  Representing statics as forces in equilibrium. , 1988, Journal of experimental psychology. General.

[34]  G. Taga,et al.  Frame of reference for visual perception in young infants during change of body position , 2007, Experimental Brain Research.

[35]  G P Bingham,et al.  Dynamics and the orientation of kinematic forms in visual event recognition. , 1995, Journal of experimental psychology. Human perception and performance.

[36]  R. Held,et al.  Moving Visual Scenes Influence the Apparent Direction of Gravity , 1972, Science.

[37]  Faisal Karmali,et al.  Mental own-body and body-part transformations in microgravity. , 2007, Journal of vestibular research : equilibrium & orientation.

[38]  A Berthoz,et al.  Mental rotation for spatial environment recognition. , 2000, Brain research. Cognitive brain research.

[39]  V. Smetácek.  Balance: Mind-grasping gravity , 2002, Nature.

[40]  N. Kanwisher,et al.  Activation in Human MT/MST by Static Images with Implied Motion , 2000, Journal of Cognitive Neuroscience.

[41]  V. Stone,et al.  The Body-Inversion Effect , 2003, Psychological science.

[42]  F. Lacquaniti,et al.  Visual perception and interception of falling objects: a review of evidence for an internal model of gravity , 2005, Journal of neural engineering.

[43]  F. Lacquaniti,et al.  Fast adaptation of the internal model of gravity for manual interceptions: evidence for event-dependent learning. , 2005, Journal of neurophysiology.

[44]  Catherine L Reed,et al.  Turning configural processing upside down: part and whole body postures. , 2006, Journal of experimental psychology. Human perception and performance.

[45]  J. Lackner,et al.  Vestibular, proprioceptive, and haptic contributions to spatial orientation. , 2005, Annual review of psychology.

[46]  R. Yin.  Looking at Upside-down Faces , 1969 .

[47]  Charles M. Oman,et al.  Human Visual Orientation in Weightlessness , 2003 .

[48]  F. Mast,et al.  Assessing Otolith Function by the Subjective Visual Vertical , 1999, Annals of the New York Academy of Sciences.

[49]  L R Young,et al.  Spatial orientation in weightlessness and readaptation to earth's gravity. , 1984, Science.

[50]  Norman G. Vinson,et al.  Sources of object-specific effects in representational momentum , 2002 .

[51]  Shinya Yamamoto,et al.  Effects of the gravitational vertical on the visual perception of reversible figures , 2006, Neuroscience Research.

[52]  M. Lacour,et al.  Visual field dependence–independence before and after unilateral vestibular loss , 2006, Neuroreport.

[53]  R. Blake,et al.  Perception of human motion. , 2007, Annual review of psychology.

[54]  J R Lackner,et al.  Spatial Orientation in Weightless Environments , 1992, Perception.

[55]  C. Bonnet,et al.  Visual Representations of Dynamic Actions from Static Pictures , 2005, Perception.

[56]  R. C. Oldfield.  The assessment and analysis of handedness: the Edinburgh inventory. , 1971, Neuropsychologia.

[57]  Hermann Aubert,et al.  Eine scheinbare bedeutende Drehung von Objecten bei Neigung des Kopfes nach rechts oder links , 1861, Archiv für pathologische Anatomie und Physiologie und für klinische Medicin.

[58]  F. Lacquaniti,et al.  Internal models of target motion: expected dynamics overrides measured kinematics in timing manual interceptions. , 2004, Journal of neurophysiology.

[59]  A. D. Van Beuzekom,et al.  Properties of the internal representation of gravity inferred from spatial-direction and body-tilt estimates. , 2000 .

[60]  Christophe Lopez,et al.  How body position changes visual vertical perception after unilateral vestibular loss , 2008, Neuropsychologia.

[61]  H Mittelstaedt,et al.  The Role of the Otoliths in Perception of the Vertical and in Path Integration , 1999, Annals of the New York Academy of Sciences.

[62]  P A Barraud,et al.  Subjective vertical and postural activity. , 1997, Acta psychologica.

[63]  W Gerbino,et al.  Retinal vs. environmental orientation in the perception of the right angle. , 1995, Acta psychologica.

[64]  F. Lacquaniti,et al.  The role of preparation in tuning anticipatory and reflex responses during catching , 1989, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[65]  T. Hubbard,et al.  Environmental invariants in the representation of motion: Implied dynamics and representational momentum, gravity, friction, and centripetal force , 1995, Psychonomic bulletin & review.

[66]  M. Candidi,et al.  Mapping Implied Body Actions in the Human Motor System , 2006, The Journal of Neuroscience.

[67]  H. A. Witkin,et al.  Studies in space orientation; further experiments on perception of the upright with displaced visual fields. , 1948, Journal of experimental psychology.

[68]  J. Freyd,et al.  The mental representation of movement when static stimuli are viewed , 1983, Perception & psychophysics.

[69]  Stephen M. Kosslyn,et al.  Visual mental imagery during caloric vestibular stimulation , 2006, Neuropsychologia.

[70]  H Mittelstaedt,et al.  Somatic versus Vestibular Gravity Reception in Man , 1992, Annals of the New York Academy of Sciences.