Decades of psycholinguistic research have witnessed a sustained interest in whether syntactic island constraints are active during sentence comprehension. This paper examines extraction from the pseudo-coordination construction - a systematic violation of Ross’ (1967) Coordinate Structure Constraint - and its treatment in online processing. I argue that pseudo-coordination constructions are composed via Non-Boolean conjunction, a different conjunction operator than other, seemingly identical, coordinate structures. The exceptional nature of extraction from pseudo-coordination structures is argued to result from the fact that this operator does not semantically distribute an argument across conjuncts. I also propose an interpretive constraint on Non-Boolean conjunction, that localizes it beneath Aspectual projections. Two experiments are presented, the results of which are consonant with the basic predictions of this account.