According to the cognitive approach to humour, understanding of humorous texts implies a moment of surprise, even confusion of thought, produced by the recognition of an incongruity, defined as an incoherent piece of the text. The problem solving activity involved in humor understanding aims at resolving the incongruity. This study's goal is to contribute to better define the surprise experience by describing its epistemic and evidential aspects. The tested hypothesis, verified through “thinking aloud method” and the descriptive tools provided by the Known-Unknown-Believed theory, is that this phase of humor understanding is linked to the worlds of knowledge of unknown and believed, referred to by means of consistent linguistic markers. The hypothesis resulted to be confirmed both for jokes and cartoons.