Signalling in IF games: a tricky business Theo M.V. Janssen, Francien Dechesne Abstract: The paper studies the phenomenon of signalling in logics for imperfect information, such as Hintikka's IF logic. It is shown that signalling is a phenomenon that at the one hand is essential for the semantics, but at the other hand is a source of tricky phenomena. Several properties which in the literature are claimed to hold for such logics, turn out to fail due to signalling: IF logic is not a conservative extension of predicate logic, renaming of variables is not always allowed, the prenex normal form theorem does not hold, and slashed connectives cannot easily be eliminated. Keywords: IF logic, Independence Friendly logic,games, imperfect information, prenex form, renaming variables, Hintikka