Proactive control · individual practice

AX-CPT

A letter (cue) → 1s pause → another letter (target). Press MATCH only on A → X; withhold otherwise. 100 trials with 70/12.5/12.5/5% (AX/AY/BX/BY) proportions (~5 min). Cohen et al. 1999 — AY/BX ratio reveals proactive vs reactive control.