Incongruity in humor: Root cause or epiphenomenon?

Humor and incongruity appear to be constant bedfellows, for at the heart of every joke one can point to some degree of absurdity, illogicality, or violation of expectation. This observation has lead many theories of humor to base themselves around some notion of incongruity or opposition, most notably the semantic-script theory (or SSTH) of Raskin and the subsequent general theory (or GTVH) of Attardo and Raskin. But correlation does not imply causality (a reality used to good effect in many successful examples of humor), and one should question whether incongruity serves a causal role in the workings and appreciation of humor or merely an epiphenomenal one. It remains a key question for humor researchers as to whether listeners react to incongruities by constructing humorous interpretations, or whether they collaboratively create these incongruities as a result of opportunistically constructing humorous interpretations.