How do our brains adapt to control an extra body part?

How the “Third Thumb” Fits Existing Human Capabilities

• Many see the findings as unsurprising given human proficiency with tools.
  • Driving, gaming controllers, musical instruments, bicycles, and motorcycles are cited as things that quickly feel like bodily extensions.
  • Concepts like “extended cognition” and affordances are invoked: we perceive the world in terms of what we can do with it, and new tools change that perception.

Motor Learning, Automaticity, and Coaching

• Personal stories of injury rehab, singing, sports, piano, martial arts, and gaming highlight that movement learning is largely subconscious.
• Discussion of a “constraints-led approach” to coaching: rather than teaching a “perfect technique,” coaches manipulate constraints so the body discovers solutions via “repetition without repetition.”
• Once low-level control is automatic, cognition shifts to high-level strategy (e.g., elite athletes recounting complex plays after the fact).

Neuroplasticity, Injury, and Phantom Sensations

• Examples include tendon rerouting after Achilles rupture, post-fracture sensory weirdness, and rapid functional remapping without explicit effort.
• Reports of hearing changes after head injury, and the brain “patching over” missing information.
• Multiple anecdotes of “phantom” devices or body parts: tails, rings, watches, phone buzzes, fursuit tails, etc., sometimes persisting long after removal.

Sensory Substitution and Extra Senses

• References to haptic compasses, tactile vision substitution (camera-to-skin matrices), magnet implants for sensing fields, and proximity hats.
• Some users adapt quickly and feel genuine loss when devices are removed, raising ethical questions.
• Open questions about where to put feedback for a third thumb (e.g., a skin patch on the back) and whether it could feel local to the thumb.

Accessibility, Design Tradeoffs, and Generalization

• Curb-cut effect is discussed: tech built for one group often benefits many others.
• Others stress tradeoffs: curb bumps slippery or less wheel-friendly in some cities, large fonts, long traffic lights, ramps, and accessible stalls impose costs or inconveniences.
• Software accessibility is framed as overlapping strongly with power-user features.

Device Design, Control, and Skepticism

• The thumb is currently toe-controlled; some suggest using underused forearm muscles via EMG for more intuitive control.
• Questions about lack of detail on the full setup and whether there is haptic force feedback.
• A few dismiss it as a “hacky kludge” rather than a true extra body part, while others are eager for open schematics and DIY versions.