Six shapes share a secret rule. Six others all break it. What's the rule?
A Bongard problem shows two small sets of simple diagrams side by side: every image on the left obeys some hidden rule, and every image on the right breaks it. The task is to work out the rule just by comparing the two groups, even though no single image gives it away and the rule itself can be almost anything — shape, count, symmetry, or something stranger.
Reveal the answer
There's no single trick — each Bongard problem hides a different rule, from 'the left shapes are convex' to 'the left figures could be drawn without lifting the pen.' Soviet cybernetician Mikhail Bongard devised a hundred such problems in his 1967 book to study how pattern recognition and concept formation work, and they later became a benchmark for testing machine vision and AI reasoning.
— Mikhail Bongard, Pattern Recognition — 1967 (Russian); English translation 1970