This study investigated the volitionality effect on split intransitivity in
Japanese with respect to licensing of floating numeral quantifiers (FNQ), a
syntactic unaccusativity diagnostic in Japanese. An acceptability judgment
experiment was conducted to examine whether volitionality represented with
the combination of an animate subject and a volitional adverbial phrase
reduces the acceptability of the FNQ sentences, assuming that volitionality
contributes to an unergative interpretation. Our results were as predicted
and concluded that volitionality is a determinant factor for dividing the
unaccusative/unergative structure in Japanese.