Brightness Discrimination Game

About Brightness

Brightness is a pure test of lightness discrimination. A grid of colored swatches fills the screen and every one of them looks the same, except for a single swatch that is a little darker or a little lighter than the rest. The question above the grid tells you which direction to look for, and you tap the swatch that does not belong.

The tint of the swatches changes from round to round: sometimes a neutral gray, sometimes a muted teal, rose or olive. That matters, because it stops you from learning one reference shade and keeps your eye working on the contrast between neighbors. Early rounds are generous, with four large swatches and a gap you can see at a glance. Later rounds use eight swatches and a gap so small that you will often doubt your own eyes.

How to play

1. Read the question: it asks for either the darker or the lighter swatch. Both directions are equally hard.
2. Scan the whole grid once without fixating on a single swatch. The odd one often reveals itself as a small flicker of contrast in your peripheral vision.
3. Tap the swatch you think is different. A tap is final, so decide first.
4. The correct swatch lights up with a green border, and a short note tells you how big the lightness difference was in that round.

All swatches look the same except one, which is a little darker or lighter. Tap the odd one out as fast as you can.

How scoring works

Every round is a one-tap answer: 100 points for the right swatch, 0 for any other. Because a wrong tap gives nothing, the game is made harder by the size of the gap, not by tricks. The gap is measured as a difference in CIELAB lightness (L*), a perceptual scale from 0 for black to 100 for white. It starts at 14 units on level 1 and shrinks to 2.2 units on level 10.

The number of swatches grows with difficulty too: four swatches on levels 1 to 4, six on levels 5 to 7 and eight on levels 8 to 10, so a blind guess succeeds 25, 17 or 12.5 percent of the time. The timer starts at 9 seconds and falls to 7 seconds. If it runs out the round scores 0, because there is no sensible answer to submit.

What it trains

This game trains contrast sensitivity, the ability to notice small differences in lightness between neighboring surfaces. It is one of the most basic building blocks of vision: edges, textures and shapes are all detected first as differences in luminance.

The skill matters when you proofread a print for banding, check whether a wall was painted evenly, notice a smudge on a screen, or pick out a worn patch on a road at dusk. Photographers and retouchers lean on it constantly when they match tones across an image.

Tips for a higher score

• Do not stare. Let your eyes relax on the center of the grid and look for the swatch that appears to glow a little differently. Staring at one swatch makes your eye adapt to it.
• Tilt your head or squint slightly. Squinting blurs fine detail and exaggerates differences in lightness, which is exactly what you are looking for.
• Raise your screen brightness a little in a dim room. Very dark screens compress the lightest and darkest shades, which hides small gaps.
• Compare each swatch with its neighbors rather than with a mental image. Relative comparison is something the visual system does extremely well, while absolute judgments are poor.
• If you cannot see a difference after two seconds, pick the swatch that your eye was drawn to first. A first impression is right more often than a long deliberation.

The idea behind it

The smallest lightness difference you can notice is roughly a constant fraction of the background lightness, a relationship known as Weber's law. For luminance the fraction is typically in the region of one to two percent under good conditions, which is why a gap of about two L* units is close to the limit of what most people can see on a phone screen.

Perceived lightness also depends on context. In simultaneous contrast, the same gray patch looks darker on a white background than on a black one. The game keeps every swatch on the same background so that only the swatch itself changes. CIELAB, the color space used here, was standardized by the CIE in 1976 to make equal numeric steps look roughly equal to a human observer.

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Free, no account. Your best scores are saved on your device.