What is the Weber fraction for size?

Around 7–10% for area discrimination under normal viewing. This means differences below 7% are difficult to detect reliably — which is exactly where the hard levels of this game operate.

Is there always exactly one odd shape?

Yes — always exactly one larger shape per round. The game never presents zero or multiple outliers.

Does shape type affect difficulty?

Yes — circles are easiest because size comparison between two circles is highly accurate. Irregular polygons are harder because area and perimeter don't scale proportionally.

Can You Find the Odd One Out?

Can you find the odd one out — the single shape that's slightly larger than all the others in the grid? A grid of seemingly identical shapes appears and exactly one is a few percent bigger. Click it. Easy when the difference is 20%; brutally hard when the size difference drops to 3%. This game probes the lower threshold of your size discrimination — how tiny a difference can your visual system reliably detect?

How to Play

A grid of shapes appears — they all look the same at first glance.
One shape is larger than the rest by a small percentage.
Click the one you think is the odd shape.
Harder modes reduce the size difference and add more shapes to the grid.

Why It's Hard

Size discrimination depends on the Weber fraction — the minimum detectable size difference as a proportion of the reference size. For visual area, this threshold is roughly 7–10% under ideal conditions. Near this threshold, your brain can't reliably distinguish signal (the larger shape) from noise (natural variation in your size perception), making correct identification near chance level.

Tips

1Don't stare at one shape — let your eyes scan the whole grid loosely. The outlier often "pops" in peripheral vision.
2Compare adjacent shapes: find two that look the same size, then scan for the one that doesn't match the pattern.
3On hard levels, compare shapes in the corners — they're harder to compare directly to the center and may stand out.

FAQ

What is the Weber fraction for size?: Around 7–10% for area discrimination under normal viewing. This means differences below 7% are difficult to detect reliably — which is exactly where the hard levels of this game operate.
Is there always exactly one odd shape?: Yes — always exactly one larger shape per round. The game never presents zero or multiple outliers.
Does shape type affect difficulty?: Yes — circles are easiest because size comparison between two circles is highly accurate. Irregular polygons are harder because area and perimeter don't scale proportionally.

Built by

Ethan R. Caldwell

Game Developer · Wilmington, DE

Designed Can You Find the Odd One Out? and 46 other browser puzzles. Game developer based in Wilmington, Delaware. Hardcore puzzle gamer at heart — obsessed with logic puzzles, sokoban-style mechanics, and physics-based brain teasers. Off the clock, unwinds with ARPGs, RPGs and JRPGs.

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