Two contacts, one explicit assumption

A silent two-contact calculation using equal Gaussian position uncertainty and a prior favoring slow motion. No stimulus is delivered to your skin. This is not a personal sensory measurement or a full rabbit-stimulus demonstration.

Physical separation: 10.0 cm Interval between contacts: 0.10 s Position uncertainty at each site: 1.00 cm

Estimated separation: 3.33 cm from a physical separation of 10.00 cm (33.3% retained).

Positions around the unchanged midpoint
Position	Physical (cm)	Estimated (cm)
Left	−5.000	−1.667
Right	5.000	1.667
Midpoint	0.000	0.000

Estimated separation = L ÷ [1 + 2σ² ÷ (100t²)].
L is physical separation in centimetres; t is time in seconds; σ is the standard deviation of each site’s Gaussian position estimate, in centimetres. The speed-prior standard deviation stays fixed at 10 cm/s, whose square is 100.

The two sites have the same uncertainty, so the midpoint stays at zero. A longer interval reduces contraction in this model. At zero uncertainty, the estimate equals the physical separation. Unequal site uncertainty needs a different rule. These are mathematical consequences of the stated assumptions, not participant observations or an assessment of anyone’s senses.