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Cybernetics · incentives

Goodhart's law of assessment

The Proxy Trap

The feedback loop reinforces the test score, decoupled from the learning it was meant to stand for.

When a measure becomes a target, it ceases to be a good measure.

The test score is a proxy for learning. Once the system rewards that proxy, with promotion, funding and status all keyed to it, every agent inside rationally optimises the proxy instead of the thing it stands for. Students cram and forget, teachers teach to the test, and the metric inflates while the competence under it stays put.

flowchart LR
  L[Actual learning] -->|measured by| S[Test score]
  S -->|rewarded by| I[Incentives]
  I -->|optimise| S
  I -.->|decoupled from| L

Why it is a system-dynamics problem

This is cybernetics and incentive design: a feedback loop whose reward signal is wired to a proxy rather than to ground truth. Telling students to “learn for real” changes nothing. The fix is to redesign the loop so the measured quantity is expensive to game and tightly coupled to real mastery, until optimising the metric and optimising the learning are the same act.