Left-sorted Bongard Problems have the keyword "left-couldbe" on the OEBP.

Right-sorted Bongard Problems have the keyword "right-couldbe".

In a "couldbe" Bongard Problem, some relevant information is left out by the way objects are displayed. Solutions to "left-couldbe" BPs sound like "Could be a ___ vs. definitely not a ___" (and vice versa for "right-couldbe" BPs.)

To put it in mathematical jargon, there is a "projection" function from objects to pictures, such that objects satisfying property X are mapped to the same picture as objects not satisfying property X. Sorted on the "couldbe" side is the image (under projection) of the collection of objects satisfying property X.

Furthermore, usually X is a relatively narrow criterion, so that most objects do not satisfy it (see keywords left-narrow and right-narrow), and all pictures are in the image (under projection) of the collection of objects not satisfying property X.

Consider BP525, "Cropped image of a circle vs. not so." None of the left-hand examples are definitely an image of a circle, but they fit left because nothing indicates that they are not an image of a circle. A more pedantic solution to this Bongard Problem would be "There is a way of cropping a circle that gives this image vs. there isn't."

See also the keyword seemslike, where neither side can be confirmed.

Either "left-couldbe" or "right-couldbe" implies notso.

Although the descriptions of "left-couldbe" and "right-couldbe" sound similar to left-unknowable and right-unknowable, they are not the same. It is the difference between a clear absence of information and perpetual uncertainty about whether there is more information to be found.

"Left-couldbe" is usually left-narrow and "right-couldbe" usually right-narrow.

Adjacent-numbered pages:
BP1154 BP1155 BP1156 BP1157 BP1158  *  BP1160 BP1161 BP1162 BP1163 BP1164

dual, meta (see left/right), links, keyword, side, viceversa

Leo Crabbe

Note that most traditional Bongard Problems don't sort an all black-panel at all.

See BP567 (left-null versus right-null) for the version about all-white panels, which is more often applicable.

Adjacent-numbered pages:
BP1155 BP1156 BP1157 BP1158 BP1159  *  BP1161 BP1162 BP1163 BP1164 BP1165

meta (see left/right), links, side, testexample

Leo Crabbe

Bongard Problems sorted left obtain the keyword "viceversa" on the OEBP.

Contrast the keyword notso.

"Viceversa" BPs are often dual.

The solution to a less-than/greater-than quantity comparison Bongard Problem (keyword spectrum) where the two sides divide the spectrum in half can be phrased as "closer to left end of spectrum than right end vs. vice versa." Whether this is a natural way to phrase the solution depends on the kind of quantity being compared.

Here are some examples of spectra for which the "vice versa" phrasing tends to seem natural: left vs. right, up vs. down, black vs. white, higher quantity of [thing type 1] vs. higher quantity of [thing type 2].

Adjacent-numbered pages:
BP1157 BP1158 BP1159 BP1160 BP1161  *  BP1163 BP1164 BP1165 BP1166 BP1167

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

Aaron David Fairbanks

Left-sorted Problems often have a specific format or deal with specific geometric shapes.

Almost any Problem that sorts the all-white or all-black panels will be sorted right.

Adjacent-numbered pages:
BP1159 BP1160 BP1161 BP1162 BP1163  *  BP1165 BP1166 BP1167 BP1168 BP1169

notso, meta (see left/right), links, problemkiller

visualbp [smaller | same | bigger]

Leo Crabbe

Any miniproblems BP with all examples in the same format will be sorted left.

See also the keyword structure.

Adjacent-numbered pages:
BP1160 BP1161 BP1162 BP1163 BP1164  *  BP1166 BP1167 BP1168 BP1169 BP1170

notso, meta (see left/right), links

visualbp [smaller | same | bigger]

Aaron David Fairbanks

Not all visual Bongard Problems whose examples all have some amount of black in them are sorted left. In left-sorted BPs, there must be some concrete percentage of black that is exceeded by every sorted example.

Adjacent-numbered pages:
BP1161 BP1162 BP1163 BP1164 BP1165  *  BP1167 BP1168 BP1169 BP1170 BP1171

meta (see left/right), links

Leo Crabbe

All left BPs would be tagged finishedexamples.

Adjacent-numbered pages:
BP1162 BP1163 BP1164 BP1165 BP1166  *  BP1168 BP1169 BP1170 BP1171 BP1172

precise, notso, meta (see left/right), links, sideless

Leo Crabbe

Adjacent-numbered pages:
BP1164 BP1165 BP1166 BP1167 BP1168  *  BP1170 BP1171 BP1172 BP1173 BP1174

notso, meta (see left/right), links, problemkiller

Leo Crabbe

Left-sorted Bongard Problems have the keyword "problemkiller" on the OEBP.

An example could be unsortable because it does not conform to the format of all the examples in the Bongard Problem, or it could be formatted like the other examples but be treated ambiguously by the solution. It seems the Bongard Problems currently labeled "problemkiller" mostly deal with examples becoming unsortable because they no longer conform to the format. (The examples become unsortable because they leave the "world" of the Bongard Problem. See https://www.oebp.org/world.php .) - Aaron David Fairbanks, Jun 15 2023

"Problemkiller" Bongard Problems are notso Bongard Problems.

See keyword invariance, which is about transformations making some example switch sides rather than transformations making all examples unsortable.

Adjacent-numbered pages:
BP1165 BP1166 BP1167 BP1168 BP1169  *  BP1171 BP1172 BP1173 BP1174 BP1175

notso, meta (see left/right), links, keyword

linksbp [smaller | same | bigger]

Leo Crabbe

Most visual BPs will be sorted left by this problem, as examples usually have white backgrounds by default.

Adjacent-numbered pages:
BP1166 BP1167 BP1168 BP1169 BP1170  *  BP1172 BP1173 BP1174 BP1175 BP1176

meta (see left/right), links, sideless, right-narrow, problemkiller

Leo Crabbe