Homuncular Flexibility: The Human Ability to Inhabit Nonhuman Avatars

This essay seeks to explicate an unorthodox idea that spans psychology, neuroscience, psychology, philosophy, and computer science called homuncular flexibility (HF). HF posits that the homunculus—the part of the cortex that maps movement and sensing of body parts—is capable of adapting to novel bodies, in particular bodies that have extra appendages or appendages capable of atypical movements. Evidence demonstrates neural plasticity in nature; for example, amputees experience cortical shifting such that their face receives extra attention in the brain after a limb is amputated. However, experiments such as the rubber hand illusion, in which people respond to rubber hands placed near their arms as if they were their actual hands, demonstrated that a person's sense of their body can be adjusted to include external objects. The recent advent of virtual reality technology, which can track physical human motions and display them on avatars, allows for the wholly new human experience of inhabiting distinctly nonhuman bodies. HF is a paradigm in which physical motions are transformed by remapping degrees of freedom from tracked movements onto an avatar. For example, if a human being were to inhabit an avatar of a lobster, controlling two of the eight lobster arms would be simply be a function of tracking the two physical arms and directly mapping those movements onto the avatar's first two arms. However, in order to control the remaining six arms, degrees of freedom that are orthogonal to the movements of the first two arms need to be measured and remapped. In this essay, we discuss advancements in neuroscience, psychology, and computer science that relate to HF. We review some preliminary studies that demonstrate how humans accommodate novel bodies. Finally, we discuss theoretical implications and practical applications relating to HF. Keywords: homuncular flexibility; avatars; tool use; body schema; virtual reality