Left examples have the keyword "contributepairs" on the OEBP.

When this keyword is added to a Problem, OEBP users are advised to add a corresponding right example for every left example they add and vice versa.

It is common for Bongard Problems to present left examples on the left side and corresponding altered versions of those examples on the right side, tweaked only slightly, to highlight the difference and make the solution easier to see (see keyword help).

This is common in more abstract Bongard Problems that admit a wide range of examples, a variety of different styles or types (e.g. BP360). Showing two versions of the same thing, one on the left and one on the right, helps a person interpret what that thing is meant to be in the context of the Bongard Problem; whatever qualities vary between the two in the pair must be relevant.

If a person cannot sort an example according to the solution property without seeing its corresponding opposite example, the Bongard Problem is invalid (see https://www.oebp.org/invalid.php ). There is no one rule dividing the sides; the solution is not a method to determine whether an arbitrary example fits left or right. See also Bongard Problems with the keyword collective, which are similarly borderline-invalid.

A BP in which each left example corresponds to a right example and vice versa could be remade as a Bongard Problem in which the left examples are the pairs. For example BP360 would turn into "a pair consisting of the ordered version of something and the chaotic version of the same thing vs. a pair of things not satisfying this relationship." This process would turn a Bongard Problem that is invalid in the sense described above into a valid one.

(See keyword orderedpair.)

In some "contributepairs" Bongard Problems there really is a natural choice of left version for every right example and vice versa (see keyword dual); in others the choice is artificially imposed by the Bongard Problem creator.

When "contributepairs" Bongard Problems are laid out in the format with a grid of boxes on either side of a dividing line, the boxes may be arranged so as to highlight the correspondence: either

A B | A B

E F | E F

G H | G H

or

A B | B A

E F | F E

G H | H G.

Adjacent-numbered pages:
BP914 BP915 BP916 BP917 BP918  *  BP920 BP921 BP922 BP923 BP924

meta (see left/right), links, keyword, oebp, right-self, instruction

bppage [smaller | same | bigger]
zoom in left (correspondence_bp)

Aaron David Fairbanks

A spot-the-difference exercise.

Arguably invalid (solution not simple).

Adjacent-numbered pages:
BP915 BP916 BP917 BP918 BP919  *  BP921 BP922 BP923 BP924 BP925

less, precise, convoluted, arbitrary, stretch, unstable, left-finite, left-full, perfect, pixelperfect, experimental, funny

bmp [smaller | same | bigger]

Aaron David Fairbanks

Adjacent-numbered pages:
BP916 BP917 BP918 BP919 BP920  *  BP922 BP923 BP924 BP925 BP926

meta (see left/right), links, metaconcept

Leo Crabbe

The mathematical terms for these operations are even and odd permutations.

Adjacent-numbered pages:
BP917 BP918 BP919 BP920 BP921  *  BP923 BP924 BP925 BP926 BP927

precise, allsorted, math, left-narrow, right-narrow, unorderedpair, preciseworld, left-listable

Leo Crabbe

Adjacent-numbered pages:
BP918 BP919 BP920 BP921 BP922  *  BP924 BP925 BP926 BP927 BP928

meta (see left/right), links, metaconcept

bp [smaller | same | bigger]

Leo Crabbe

All examples in this Problem are outlines of convex polygons.

This is a generalisation of scalene triangles to any polygon.

The left side implies the right side of BP329 (regular vs. irregular polygons), but the converse is not true.

The left side of BP329 implies the right side, but the converse is not true.

Adjacent-numbered pages:
BP919 BP920 BP921 BP922 BP923  *  BP925 BP926 BP927 BP928 BP929

Any scalene triangle will fit on the left, because no two sides are equal.

However, any regular polygon will not fit on the left, because all of its sides are equal.

A random convex polygon will "almost surely" fit on the left.

nice, stretch, right-narrow, traditional

polygon_outline [smaller | same | bigger]

Jago Collins

Adjacent-numbered pages:
BP920 BP921 BP922 BP923 BP924  *  BP926 BP927 BP928 BP929 BP930

math, unorderedpair, traditional

two_dot_clusters [smaller | same | bigger]

Aaron David Fairbanks

Adjacent-numbered pages:
BP921 BP922 BP923 BP924 BP925  *  BP927 BP928 BP929 BP930 BP931

nice, math, sequence, traditional, left-listable, right-listable

dot_clusters_sequence_horizontal [smaller | same | bigger]

Aaron David Fairbanks

All examples are Bongard Problems fitting left or right in BP793.

All examples here are in the conventional format, i.e. white background, black vertical dividing line, and examples in boxes on either side.

Border cases are Bongard Problems that always self-sort one way given their particular visual format (e.g. fixed number of boxes), but self-sort a different way in another slightly different format.

Meta Bongard Problems appearing in BP793 that are presentationinvariant necessarily fit right here.

It is interesting to think about how this Bongard Problem sorts itself. The only self-consistent answer is that it fits right.

See BP793 "sorts self left vs. sorts self right".

See BP944 "sorts every BP on one side vs. doesn't".

Adjacent-numbered pages:
BP922 BP923 BP924 BP925 BP926  *  BP928 BP929 BP930 BP931 BP932

hard, solved, presentationinvariant, visualimagination

boxes_bpimage_sorts_self [smaller | same | bigger]
zoom in left (boxes_bpimage_sorts_self_incarnation_dependent) | zoom in right

Aaron David Fairbanks

Zero, one, or two objects may technically form a sequence, but if ALL examples of a BP have zero, one, or two objects, we do not consider that BP to be about sequences.

See BP929 for distinction between sequences of arbitrary length and sequences of fixed length (keywords "sequence" and "fixedsequence").

Adjacent-numbered pages:
BP923 BP924 BP925 BP926 BP927  *  BP929 BP930 BP931 BP932 BP933

stub, meta (see left/right), links

bp [smaller | same | bigger]
zoom in left (sequence_visualbp)

Aaron David Fairbanks