Visual Working Memory: Change Detection & ROC Phase Plane

How many things can you actually hold in mind at once? This 2D simulator runs the classic change-detection task from visual working-memory research: a study array of colored squares scattered across the stage flashes briefly, vanishes for a blank retention delay, and a test array asks whether anything changed. Instead of just reporting a number, every trial's hit/miss/false-alarm outcome is plotted live on an independently computed signal-detection ROC phase plane, where diagonal iso-capacity lines trace Cowan's formula K = N × (hit rate − false-alarm rate) — letting you watch your own operating point settle onto the K ≈ 3–4 diagonal that defines the empirical "magic number" capacity limit in cognitive psychology.