Comprehenders frequently respond “two” when asked “how many animals of each
kind did Moses bring on the ark?”, even when they know the biblical story
is about Noah, not Moses. This phenomenon is well-established, though the
mechanisms that give rise to it are not yet clear. We show that there is
substantial variability across illusion stimuli that is not predicted by
prior theories, and that this variability can shed light on the underlying
mechanism. We suggest that at least two key components are responsible: a
shift in attention away from bottom-up lexical processing, and a high
degree of contextual fit.