Very often we hear people say "he is so stupid/dumb that he can't even do ...". Today, I heard such things using standards such like "can't count", "can't form a sentence", etc. Also we hear people judge others' ignorance based on "she doesn't even know the capital of France" or judge others' fashion tastes using "he wore white socks with black shoes?!"
This reminds me of those kind of scoring tests for depression, anxiety etc. Since there is no scale for the "amount" of depression you feel, we need to score you using a limited number of very specific things you feel or don't feel.
I think everyone may unconciously have a list of things that he/she thinks everyone should know. Also unconciously they will use these things to judge others. It would be interesting to see the differences between these individual invisible IQ tests. Sure, there must also be invisible personality tests.