Previous research has hypothesized default interpretive biases for three types of ambiguities with English logical words and, or, and not. First, disjunction (A or B) is hypothesized to be biased towards an exclusive interpretation in upward-entailing environments and an inclusive interpretation in downward-entailing environments (Levinson 2000, Chierchia 2004, Breheny et al. 2005). A negated disjunction (not A or B) is claimed to be biased towards a “neither-nor” interpretation (i.e. wide scope negation: ¬[A ∨ B]) and a negated conjunction is said to be biased towards an “either-not” interpretation (i.e. wide-scope negation: ¬[A ∧ B]) (Szabolcsi 2002, Szabolcsi & Haddican 2004). We tested these hypotheses within the same experimental paradigm with 149 English-speaking participants and found disjunction to be biased towards an inclusive interpretation across three different entailment environments: episodic declaratives, questions, and conditional antecedents. Our results also confirmed that English negated disjunction is biased towards a “neither-nor” (wide scope negation) interpretation but the results did not show an “either-not” bias (wide scope negation) for negated conjunction.