Gaze for at least 10 s at the fixation cross in the neighbouring dynamic image. This will adapt your eyes to a brightening patch (above) and a repetitively dimming patch (below). Then move the mouse* over the panel to turn it into a steady gray. You should see an aftereffect of apparent dimming (above) and apparent brightening (below). Move the mouse away to re-adapt.
This demonstrates the existence of transient visual pathways selective for gradual changes of luminance.
|*On a touch device, tap the image. To “untap”, tap on the icon top right.|