Before you can blink (Pre-attentive Processing)

Some visual differences register the instant you look. A single red dot in a field of grey ones seems to announce itself — you haven't searched for it, it is just there. This is pre-attentive processing: your visual system reads a few basic features, colour among them, everywhere at once, before focused attention gets involved. The catch is that it holds for only one feature at a time. Add a second and a third competing colour and the shortcut breaks down, and you are back to checking items one by one. This demo puts that to the test with a quick counting task: glance at a grid of digits, then say how many of one digit you saw.

Choose a digit to look for, a grid size, and how long the grid shows. Press Start — the grid flashes, then disappears, and you enter how many you think you saw. Start with colours off and run a few rounds, then add them one at a time. Your accuracy for each setting builds up on the chart below.

What this teaches: Count a target among distractors using one, two or more colours to see when it stands out instantly and when it doesn't. It teaches pre-attentive processing, the limits of colour as a visual cue, and why too many colours defeat it.