  George A. Miller said that human beings have only seven chunks in short-term
memory, plus or minus two. We counted the number of bunsetsus (phrases) whose
modifiees are undetermined in each step of an analysis of the dependency
structure of Japanese sentences, and which therefore must be stored in
short-term memory. The number was roughly less than nine, the upper bound of
seven plus or minus two. We also obtained similar results with English
sentences under the assumption that human beings recognize a series of words,
such as a noun phrase (NP), as a unit. This indicates that if we assume that
the human cognitive units in Japanese and English are bunsetsu and NP
respectively, analysis will support Miller's $7 \pm 2$ theory.
