Bongard problem

A Bongard problem is a kind of puzzle invented by the Soviet computer scientist Mikhail Moiseevich Bongard, probably in the mid-1960s. They were published in his eponymous 1967 book on pattern recognition, which became known in English translation from 1970. Bongard in the introduction to the book, which deals with a number of topics including perceptrons, credits the ideas in it to a group including M. N. Vainstvaig, V. V. Maksimov, and M. S. Smirnov.

The idea of a Bongard problem is to present two sets of relatively simple diagrams, say A and B. All the diagrams from set A have a common factor or attribute, which is lacking in all the diagrams of set B. The problem is to find or formulate, convincingly, the common factor.

The problems were relevant to the early days of machine learning. They were popularised by their occurrence in the 1979 book Gödel, Escher, Bach by Douglas Hofstadter, himself a composer of Bongard problems. The Bongard problem is also at the heart of the game Zendo.