The cause of laughter in every case is simply the sudden perception of the incongruity between a concept and the real objects which have been thought through it in some relation, and laughter itself is just the expression of this incongruity. It often occurs in this way:
Barrea beti kontzeptu baten eta objektu errealen artean bat-batean hautemandako inkongruentziatik sortzen da eta ez beste ezertatik, zeinaren bitartez nolabaiteko harremanean pentsatuak izan baitira, eta bera ere inkongruentzia horren adierazpena besterik ez da.