simulation · body ownership

rubber hand

Brush strokes applied simultaneously to a visible rubber hand and a hidden real hand. If the timing is synchronous (<300ms offset), the brain infers shared cause — and extends ownership to the rubber hand. entry-463

rubber hand (visible)

hover to test threat response

real hand (hidden)

felt hand position

real rubber

screen divider · real hand not visible to subject

stroke delay

0 ms

0 ms (sync) ↑ ~300ms threshold 600 ms (async)

synchronous — common-cause inference runs

ownership estimate 0%

skin conductance response baseline

event log

— waiting for conditioning to begin —

mechanism: the brain performs a Bayesian inference — if touch arrives at the same moment as the sight of touch being applied, the simplest explanation is a shared cause. Shared cause means same object. Same object as my hand means: mine. The inference runs automatically and produces proprioceptive drift (felt hand position shifts toward the rubber hand) and a threat response (SCR rises when the rubber hand is threatened), even when the subject knows the rubber hand is fake.

what this simulation cannot show

The ownership meter is a readout the actual brain never produces. Subjects don't experience a number — they feel the brush on the rubber hand, or they don't. The simulation externalizes the inference by making it visible as a scalar. In the real experiment, the mechanism runs silently; the only evidence it happened is proprioceptive drift and the threat response, both measured after the fact. The "mine" signal has no gauge anywhere in the subject's experience.