The aim of this paper is to assess whether inferences resulting from violating the principle Maximize Presupposition behave differently from presuppositions and implicatures in processing, thus testing predictions of theories which separate those inferences out from these more well-studied aspects of meaning (Percus 2006, Sauerland 2008). We present data from a picture selection task and a visual world eye-tracking study on the English indefinite/definite determiner. Based on the findings we argue that 1) the epistemic status of anti-uniqueness inferences is much weaker than the uniqueness presupposition of the definite or implicature raised by the indefinite, and 2) drawing these inferences requires more effort than not drawing it or calculating presuppositions or implicatures.