Expertise reversal

The point at which unchanged instructional support crosses from help to interference, because the learner now holds internally the schema the support supplies externally and must reconcile the two. Named by Kalyuga, Ayres, Chandler and Sweller in 2003 and explained by the redundancy effect. The threshold sits in the person rather than in the material, which is why a system that scores only content difficulty cannot see it and is imposing load on one of its two populations continuously without knowing which. Distinct from the crutch effect, which is atrophy detectable only after the help is withdrawn; expertise reversal is interference during the session itself.