The instability of human bipedalism demands that the brain accurately senses balancing self-motion and determines whether movements originate from self-generated actions or external disturbances. Here, we challenge the longstanding notion that this process relies on a single representation of the body and world to accurately perceive postural orientation and organize motor responses to control balance self-motion. Instead, we find that the conscious sense of balance can be distorted by the corrective control of upright standing. Using psychophysics, we quantified thresholds to imposed perturbations and balance responses evoking cues of self-motion that are (in)distinguishable from corrective balance actions. When standing immobile, participants clearly perceived imposed perturbations. Conversely, when freely balancing, participants often misattributed their own corrective responses as imposed motion because their balance system had detected, integrated, and responded to the perturbation in the absence of conscious perception. Importantly, this only occurred for perturbations encoded ambiguously with balance-correcting responses and that remained below the natural variability of ongoing balancing oscillations. These findings reveal that our balance system operates on its own sensorimotor principles that can interfere with causal attribution of our actions, and that our conscious sense of balance depends critically on the source and statistics of induced and self-generated motion cues.

Unperceived motor actions of the balance system interfere with the causal attribution of self-motion

School of Kinesiology, University of British Columbia , Vancouver, BC V6T 1Z1, Canada

Institut PPRIME (UPR3346), Université de Poitiers ENSMA, CNRS , 86360 Chasseneuil-du-Poitou, France

Centre de Recherches sur la Cognition et l'Apprentissage (UMR 7295), Université de Poitiers, Université de Tours, CNRS , 86073 Poitiers, France

Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam , Rotterdam 3015 GD, The Netherlands

School of Physical Education, Sport, and Exercise Sciences, University of Otago , Dunedin 9054, New Zealand

Faculty of Kinesiology, University of Calgary , Calgary, AB T2N 1N4, Canada

Department of Biomechanical Engineering, Delft University of Technology , Delft, The Netherlands

Institute for Computing, Information & Cognitive Systems, University of British Columbia , Vancouver, BC V6T 1Z4, Canada

Djavad Mowafaghian Center for Brain Health, University of British Columbia , Vancouver, BC V6T 1Z3, Canada