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<Paper uid="W05-0509">
  <Title>subject/object learning</Title>
  <Section position="7" start_page="79" end_page="80" type="concl">
    <SectionTitle>
7 General discussion
</SectionTitle>
    <Paragraph position="0"> It appears that the distributional evidence of high frequency light verbs may well provide a solid cognitive anchor for sweeping perceptual generalizations on the syntax-semantics mapping. These generalizations are local, in that they involve pos itional NV and VN pairs only, and are perceptual as they address the issue of identifying appropriate syntactic relations by relying on perceptual features of linguistic contexts, such as position, animacy, etc. On the basis of these findings, one can reasonably argue that complex lexical constructions (in the sense of Goldberg 1998) are built upon these local patterns, by combining them in those contexts where the presence of a particular verb licenses such a combination.</Paragraph>
    <Paragraph position="1"> The two feature configurations discussed in SS.5 (i.e. NLC and LC) can thus be viewed as two successive steps along the path that leads towards the emergence of complex, lexically-driven constructions. This can actually be modeled as the incremental process of adding more and more lexical constraints to early lexicon-free generalizations (based on word order, animacy, definiteness etc.).</Paragraph>
    <Paragraph position="2"> As a result of such additional constraints, the presence of an intransitive verb may completely rule out the object interpretation of a VN pattern, flying in the face of a general bias towards viewing VN as a transitive pattern. This picture is compatible with the well-known observation that constructions are used rather conservatively by children at early stages of language maturation (Tomasello 2000).</Paragraph>
    <Paragraph position="3"> In fact, if early generalizations are mainly perceptual and local, we do not expect them to be used in production, at least until the child reaches a stage where they are combined into bigger lexically-driven constructions.</Paragraph>
    <Paragraph position="4"> ME has proven to be a sound computational learning framework to simulate the interplay of complex probabilistic constraints in language. Our experiments confirm linguistic generalizations and psycholinguistic data for subjects and objects in Italian, while raising new interesting issues at the same time. This is the case of the role of definiteness in SOI. In fact, the model features neatly reproduce the definiteness markedness hierarchy, but definiteness does not appear to be really influential for subject and object processing. Various hypotheses are compatible with such results, inclu ding that definiteness is not a cue on which speakers rely for SOI in Italian. Another more interesting possibility is that definiteness constraints may indeed play a decisive role when the learner is asked to assign subject and object relations in the context of a more complex construction than a simple NV pair. Suppose that both nouns of a noun-noun-verb triple are amenable to a subject interpretation, but that one of them is a more likely subject than the other due to its being part of a definite noun phrase. Then, it is reasonable to expect that the model would select the definite noun phrase as the subject in the triple and opt for an object interpretation of the other candidate noun phrase.</Paragraph>
    <Paragraph position="5"> As part of our future work, we plan to train the ME model on a more realistic corpus of parental input to Italian children, available in the CHILDES database (MacWhinney, 2000: http://childes.psy.</Paragraph>
    <Paragraph position="6"> cmu.edu/data/Romance/Italian). In fact, there is converging evidence that the use of particular constructions in parental speech is largely dominated by the use of each construction with one specific, highly frequent verb (e.g. go for the intransitive construction). The same trends noted in mother's speech to children are mirrored in children's early speech (Goldberg et al., 2004). Quochi (in preparation) reports a similar distributional pattern for the caused motion and intransitive motion verbs in two Italian CHILDES corpora (named &amp;quot;Italian-Antelmi&amp;quot; and &amp;quot;Italian-Calambrone&amp;quot;). If these findings are confirmed, the high accuracy of our ME model trained on the skewed frequency corpus (SF) allows us to expect an equally high accuracy when training the model on evidence from Italian parental speech.</Paragraph>
    <Paragraph position="7"> This brings us to another related point: lack of correction/supervision in parental input. Since our ME model heavily relies on previously classified noun-verb pairs, we can legitimately wonder how easily it can be extended to simulate child language learning in an unsupervised mode. In fact, it should be appreciated that, in our experiments, compartively little rests on supervised classification. Iden- null tification of the contextually-relevant subject is, for lack of explicit morphosyntactic clues such as agreement and diathesis, simply a matter of guessing the more likely agent of the action expressed by the verb on the basis of semantic and pragmatic features such as animacy, definiteness and noun position to the verb. Mutatis mutandis, the same holds for object identification. It is then highly likely that salient evidence for the correct subject/object classific ation comes to the child from dir ect observation of the situation described by a sentence. It is such systematic coupling of linguistic evidence from the sentence with perceptual evidence of the situation described by the sentence that can assist the child in developing interface notions such as subject, object and the like.</Paragraph>
  </Section>
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