Click the red T as soon as you see it. In feature search, distractors are green Ts; colour alone should keep the slope near zero. In conjunction search, red Ls and green Ts share the target’s features, so reaction time is expected to increase with set size.
Arts fork: make a field you would hang, then test whether beauty helped or hid the target. Science fork: add a target-absent key, or a third set size, by editing this page.