Causality and Point of View in Japanese Complex Sentences


Dept. of Electronics and Computer Engineering, Yokohama National University
156 Tokiwadai, Hodogaya, Tokohama, 240, JAPAN

We focus here on the semantics of complex sentence that expresses a causality relation. Fortunately in complex sentence we can usually identify the discourse relation between subordinate and main clause in virtue of conjunctive particles. So, we pursue the coreference problem by fully utilizing the discourse relation known from these conjunctive particles.
The main target of this research is a complex sentence that describes a situation in which a human feels something emotionally or physically and then responds to it by doing some action or having a new emotion. Namely what we deal with is a complex sentence which describes a causality relation and uses a conjunct like {node} (`because' or `since' in English) in Japanese. To capture this kind of causality relation, the following notion is needed.
Definition: {Motivated} is a person who is so strongly effected by the situation described by the subordinate clause that s/he acts as described by the main clause.
Usually a {motivated} which is one of the roles appearing in the subordinate clause corresponds to the matrix subject. The problem we pursue in the rest is who is preferred as a {motivated} from among roles appearing in the subordinate clause. For this, we will examine a number of examples hereafter.
We start with an example which does not have a modality part in subordinate clause. Note that intuitive interpretations follow just after a sentence, henceforth.

$[\phi_{sub-s}$ & kurusii & node],
& feel bad & because
$\phi_{sub-m}$ & kusuri-o & non-da.
& medicine & took

`Since $\phi_{sub-s}$ felt bad, $\phi_{sub-m}$ took a medicine.'
$\phi_{sub-s} = \phi_{sub-m}$}
This example does not have a modality part. That means that no other role are introduced in the subordinate clause besides the semantic role {experiencer} of feeling pain or bad. And in intuitive interpretations, these semantic roles corefer with the matrix subjects respectively. In general, in this type of subordinate clause, a { motivated} is the semantic role {experiencer} of proposition part that often corresponds to the grammatical subject of subordinate clause.

$[\phi_{sub-s}$ & kurusi & -gat-ta & node],
& feel bad & behaved like & because
$\phi_{sub-m}$ & kusuri-o & atae-ta.
& medicine-ACC & gave

`Since $\phi_{sub-s}$ behave like feeling bad, $\phi_{sub-m}$ gave a medicine.'
$\phi_{sub-s} \neq \phi_{sub-m}$}
In (\ref{40}), modality expression {-gat} (`behave like --ing') are used. Then these expressions introduce a pragmatic role {observer} who observes the situation described by the subordinate clause. {Observers} are not explicitly expressed in the subordinate clauses. Nevertheless in intuitive interpretations of (\ref{40}), it appears as the matrix subjects. In our term, as the referent of {motivated} a semantic role of experiencer of subordinate clause is overridden by a pragmatic role {observer} introduced by the modality part {gat}. Let's see the cases in which the point of view expression is used in a subordinate clause.

$[\phi_{sub-s}$ & tasuke & -tekure-ta & node],
& help & -GIVEN-PAST & because
$\phi_{sub-m}$ & totemo & kansha-si & -teiru.
& very & thank & -PERFECT

`Since $\phi_{sub-s}$ helped, $\phi_{sub-m}$ felt the great thanks.'
$\phi_{sub-s} \neq \phi_{sub-m}$}
Japanese point of view expression {-tekurer} introduces a { beneficiary} who gets a certain benefit from the action described by the verb phrase to which {-tekurer} is attached. And in intuitive interpretation, the introduced {beneficiary} comes to be a { motivated} which actually is the matrix subject. In fact, an { affectee} of passive coincides with {beneficiary} of {-tekurer} in our framework. In (\ref{50}), the {beneficiary} coincides with the point of view. However in {-teyar} (`GIVE') case, the point of view is a subject, and the {beneficiary} is an object. In this kind of cases, of course, a {motivated} is not a point of view but a {beneficiary}, for instance shown in the intuitive interpretations of the following examples.

$[ \phi_{sub-s}$ & ronbun -o & otosi & -teyat-ta
& paper-ACC & reject & -GIVE-PAST
node], & $\phi_{sub-m}$ & okot-ta.
because & & got angry

`Since $\phi_{sub-s}$ intentionally rejected $\phi_{ben}$'s paper, $\phi_{sub-m}$ got angry.'
$\phi_{sub-s} \neq \phi_{sub-m} = \phi_{ben}$}
In Japanese, the combination of point of view expressions and passive form, for instance, verb{-are-teyaru} (passive morphoneme {-are} plus -teyar) are often used. In this kind of case, a pragmatic role introduced by the last expression is taken as a {motivated}. Namely in {-are-tryar} case, it is a beneficiary of {-teyar}.
So far, we have dealt with interpretations based only on voice, modality and point of view. But we have to think of the priority among interpretations based on these linguistic factors and those based on commonsense knowledge.

$[ \phi_{sub-s}$ & takusan & sigoto-o & sita
& a lot of & work-ACC & did
node $]$, & $\phi_{sub-m}$ & tukare-ta.
because & & got tired

$\phi_{sub-s} = \phi_{sub-m}$}
Here the intuitive interpretation comes from the commonsense knowledge. However in the following example,

$[ \phi_{sub-s}$ & takusan & sigoto-o & si
& a lot of & work-ACC & did
-tekure-ta & node $]$, & $\phi_{sub-m}$ & tukare-ta.
-BE GIVEN & because & & got tired

$\phi_{sub-m}$ = Beneficiary of the subordinate clause.}
we try to seek a background in which the matrix subject, namely { motivated}, can be interpreted as the beneficiary of {-tekure}, because for Japanese natives the interpretation of $\phi_{sub-s} = \phi_{sub-m}$ is pragmatically unacceptable. As such a background, for instance, we think of the situation like the following. $\phi_{sub-s}$ is a boss of $\phi_{sub-m}$. Therefore the boss's working for $\phi_{sub-m}$ makes $\phi_{sub-m}$ feel nervous, and $\phi_{sub-m}$ mentally gets tired. From these observations, we know that Japanese point of view expression like {-tekurer}, {-teyar}, etc. have so strong linguistic power that an interpretation based on commonsense knowledge can be overridden.
Finally we show a statistical data for Japanese. We gathered 205 Japanese complex sentences conjuncted by {node} from Japanese novels written by Souseki Natsume, Yokio Mishima, Sin-ich Hoshi, Banana Yoshimoto, Osamu Souda and Teru Miyamoto etc, and from the articles of Japanese journal ``Asahi Journal''. Within them, 56 sentences are of type that a subordinate clause describes a human's emotional experience and the main clause describes the action which is done by a certain human. In all the sentences of this type, the referents of motivated predicted by our theory coincides with those we get intuitively. At the judgement for interpretations, if a zero pronoun is used, we fill it by asking Japanese natives. If proper name is used, we just compared it with the prediction of our theory. Since in these examples, we find no exceptional cases, we confirmed the validity of our theory.

Keywords: Japanese, complex sentences, point of view, causality