Occupational Therapy Peg-Transfer Simulator

Patient Motor Profile

Motor control level 65%

Tremor / spasticity 25%

Peg width (task difficulty)

Nine-Hole Peg Test

Ready — press Run trial

Completion time

0.00 s

Pegs dropped

0 / 9

Trial #

Power-law prediction

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How it works

The Nine-Hole Peg Test is a real occupational-therapy assessment of fine motor dexterity: a patient transfers nine pegs, one at a time, from a tray into a pegboard as fast as accuracy allows. Each transfer's movement time follows Fitts' Law, the standard model of aimed hand movement:

MT = a + b · log2(2D / W)
  D = distance from tray to hole
  W = peg width (harder task ⇒ smaller W ⇒ longer MT)
  a, b = empirical constants (reaction + motor-unit time)

Effective movement speed also scales with the patient's motor control level, and each transfer carries a drop probability driven by tremor / spasticity:

P(drop) = clamp(0.9·tremor − 0.15·control + difficulty, 0.03, 0.95)

An assistive grip cuff halves the effective tremor term, trading a little speed for reliability — a real compensatory strategy in hand-therapy practice. Across repeated trials, performance follows the classic power law of practice (Newell & Rosenbloom, 1981): effective control improves with trial count n as

controlEff(n) = control + gain · (1 − n^−0.3)

so completion time predictably shortens over successive trials even with the same underlying impairment — exactly the recovery curve an OT tracks in a real treatment plan.

Hand / grasp point Peg in transit Dropped peg

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