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Floating constraints in lexical choice
Lexical choice is a computationally complex task, requiring a generation system to consider a potentially large number of mappings between concepts and words. Constraints that aid in determining which word is best come from a wide variety of sources, including syntax, semantics, pragmatics, the lexicon, and the underlying domain. Furthermore, in some situations, different constraints come into play early on, while in others, they apply much later. This makes it difficult to determine a systematic ordering in which to apply constraints. In this paper, we present a general approach to lexical choice that can handle multiple, interacting constraints. We focus on the problem of floating constraints, semantic or pragmatic constraints that float, appearing at a variety of different syntactic ranks, often merged with other semantic constraints. This means that multiple content units can be realized by a single surface element, and conversely, that a single content unit can be realized by a variety of surface elements. Our approach uses the Functional Unification Formalism (FUF) to represent a generation lexicon, allowing for declarative and compositional representation of individual constraints
Integrating perceptual, semantic and syntactic information in sentence production
The experimental work and the theoretical model presented in this thesis explore the behaviour of the sentence production system in perceptually, conceptually, and syntactically changing environments across languages. Nine experiments examine how speakers of different languages integrate available perceptual, conceptual, and syntactic information during production of sentences. Such integration occurs under the global control of canonical causality and automated syntax. Analysis of speakers' performance in perceptually manipulated setting demonstrated that perceptual motivations for word order alternation are relatively weak and limited to the initial event apprehension. In addition, salience-driven choices of word order are realized differently in different syntactic structures and in languages with different grammatical systems. Combining perceptual and conceptual priming paradigms did not substantially improve cueing efficiency. Contrasting, early availability of lexical and syntactic information led to the most consistent alternation of the work order.
I conclude that the uptake of perceptual information does not directly influence structural processing. General cognitive processes, such as attentional control and higher memorial activation actively contribute to the concept's accessibility status, but the syntactic organization of a spoken sentence constitutes a relatively independent psychological reality that can be realized partially as a product of the aforementioned operations but does not directly depend on them
Approximate text generation from non-hierarchical representations in a declarative framework
This thesis is on Natural Language Generation. It describes a linguistic realisation
system that translates the semantic information encoded in a conceptual graph into an
English language sentence. The use of a non-hierarchically structured semantic representation (conceptual graphs) and an approximate matching between semantic structures allows us to investigate a more general version of the sentence generation problem
where one is not pre-committed to a choice of the syntactically prominent elements in
the initial semantics. We show clearly how the semantic structure is declaratively related to linguistically motivated syntactic representation — we use D-Tree Grammars
which stem from work on Tree-Adjoining Grammars. The declarative specification of
the mapping between semantics and syntax allows for different processing strategies
to be exploited. A number of generation strategies have been considered: a pure topdown strategy and a chart-based generation technique which allows partially successful
computations to be reused in other branches of the search space. Having a generator
with increased paraphrasing power as a consequence of using non-hierarchical input
and approximate matching raises the issue whether certain 'better' paraphrases can be
generated before others. We investigate preference-based processing in the context of
generation
Verbal comprehension after brain damage :a psycholinguistic investigation with special reference to cerebro-vascular accident
PhD ThesisA review of theory and practice in the examination of verbal
comprehension in brain-dairiaged adults leads to the conclusion that this
underdeveloped area of study can benefit from the application of
theories from linguistics.
An experimental investigation of (principally) adults who had
suffered cerebro -vascular accident applied, amoxigst other linguistic
theories, the division of language into phonological, syntactic and
semantic levels of organization. The main findings were:
a) Semantic abilities in speech and comprehension corresponded;
syntactic abilities in speech corresponded with those in reading
comprehension, but not aural comprehension; comprehension of phonemic
distinctions corresponded with phonetic articulatory abilities, but
not with degree of phonemic paraphasia. Tests of verbal comprehension
which required simple manipulations of-objects or tokens were
contaminated by gesture dyspraxia. Functional comprehension was not a
reliable predictor of results on linguistic tests.
b) Piphasic adults with left-brain damage experienced significantly
more difficulties in comprehension when sequence was critical to the
meaning of a word or sentence. At the syntactic level this occurred with
reading as well as with aural input, indicating a central difficulty
rather than one which is modality-specific. in aural comprehension, unlike all
types of control subjects including children, aphasic adults found sentences
with reversible elements in surface structure harder than sentences in which
reversible deep relations are not made explicit in surface structure sequence.
Sequencing appears to be a significant influence on verbal comprehension after
left-brain damage.
c) Right-brain-damaged adults who were not aphasic in speech, and who
were familial right-handers, were selectively impaired in semantic comprehension.
Semantic comprehension may be bilaterally represented in the brain, although
comprehension at syntactic and phonological levels may depend principally on
mechanisms lateralized to the left hemisphere.Ridley Fellowship, Newcastle University
Investigation of neuronal structures and networks on the modulation of decision-making and impulse control by temporary inactivation via local microinfusion of the GABAA receptor agonist muscimol in rats
Impulsivity is determined by deficits in decision-making (impulsive choice) and impulse control (impulsive action). Using reversible inactivation via microinfusion of the GABAA receptor agonist muscimol the thesis aimed to elucidate the participation of the ventral medial prefrontal cortex (vmPFC), the nucleus accumbens (NAc) core and shell as well as the connections of the vmPFC and the NAc subregions in both forms of impulsivity in rats. The present results indicate that impulse control is regulated by both structures, while impulsive decision-making is principally modulated by the NAc, and not the vmPFC. The current investigation suggests both functional dissociations and close interactions between the vmPFC and NAc in terms of impulsive action, depending on the involved accumbal subregion. The NAc shell constitutes the critical region mediating both types of impulsivity, whereas the NAc core seems to be implicated in non-specific impairments beyond impulsive choice. Consequently, this work points towards various specific frontostriatal systems differentially contributing to delay-based decision-making and particularly impulse control
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