Andrew John Merrison, Anne H. Anderson and Gwyneth Doherty-Sneddon
An investigation into the communicative abilities of aphasic subjects
in task oriented dialogue
This paper reports on research into three mild to moderate non-fluent
Broca-type aphasics engaged with a non-aphasic partner in task
oriented dialogue. The research aimed to address the relationship
between linguistic and communicative skills of aphasic subjects, in
particular, how it is that they can sometimes communicate better than
their linguistic abilities would initially suggest. The results
indicate that at least some aphasic individuals can compensate for
their linguistic deficits (a) by effective and sensitive use of
non-verbal gesture (producing on average up to eighteen times as much
information carrying gesture than do non-aphasics engaged in the same
task) and (b) by relying on the communicative expertise of their
non-impaired partner.
(June 1994; 25 pages)
Ref. No. HCRC/RP-50 Price: UKL 1.10
Keith Stenning
Logic as a foundation for a cognitive theory of modality assignment
A cognitive theory of modality allocation has to explain the different
cognitive consequences of assigning the same information to different
modalities of expression---crudely,
which picture is worth which thousand words?
Most theories of the benefits of graphical representations have
focussed on {\it visual} properties of graphics. This talk will sketch
a theory which focusses on general logical/computational
properties of graphics. The theory is based on the proposition that
graphical representations are weakly expressive, in a logical sense,
and that this explains graphics' processing advantages. The theory
distinctively predicts that graphics will be worse than language when
graphics' logical inexpressiveness impedes abstraction that is
necessary for a task.
The general theory will be illustrated by an analysis of the use of
Euler's Circles to solve syllogisms. Earlier misinterpretations of
Euler's system by psychologists illuminate the distinctions the present
theory draws between minimally abstractive representation systems
(MARS), limited abstraction representation systems (LARS), and
unlimited abstraction representation systems (UARS). The analysis
reveals model-theoretic properties of this logical fragment which
explain why it can be captured by Euler's system. Euler's and Venn's
diagrammatic systems are both based on the analogy of spatial
containment for set membership. The basis of the difference in their
expressive power is revealed by this approach. Euler's graphical
algorithm is then generalised and the cognitively fruitful
geometrical limitation to circles
is related to the logical limitations of the generalised system.
The example analysis of Euler's Circles is then related back to the
cognitive theory of graphics and the role that logic plays in this
approach to modality allocation.
(June 1994; 15 pages)
Ref. No. HCRC/RP-51 Price: UKL 1.00
E. G. Bard, D. Robertson, and A. Sorace
Magnitude Estimation of Linguistic Acceptability
Judgments of linguistic acceptability constitute an important source of
evidence for theoretical and applied linguistics, but are typically
elicited and represented in ways which limit their utility. This paper
describes how @c[magnitude estimation], a technique used in
psychophysics, can be adapted for eliciting acceptability judgments.
Magnitude estimation of linguistic acceptability is shown to solve the
measurement scale problems which plague conventional techniques; to
provide data which makes fine distinctions robustly enough to yield
statistically significant results of linguistic interest; to be usable
in a consistent way by linguistically naive speaker-hearers, and to
allow replication across groups of informants. Methodological pitfalls
are discussed and suggestions are offered for new approaches to the
nature and measurement of linguistic acceptability.
(July 1994; 42 pages)
Ref. No. HCRC/RP-52 Price: UKL 1.60
Robert Inder and Jussi Stader
Bags and Viewers: a Metaphor for Intelligent Database Access
We present a way of structuring a database query system to form a bridge
between current data handling systems and the data requirements of
creative work. The interface is based around specifying the contents of
``bags'' of objects and inspecting them using ``viewers'', which can
then be used to launch further queries.
The operation of such an interface is described and illustrated by an
example session using a prototype system. A number of features of such
an interface are presented, the metaphor is discussed and a number of
areas for future work are indicated.
(December 1994; 18 pages)
Ref. No. HCRC/RP-53 Price: UKL 1.00
Rosemary J. Stevenson, Rosalind A. Crawley and David Kleinman
Thematic Roles, Focus and the Representation of Events
Two experiments investigated the focusing properties of thematic roles,
while a third experiment investigated the view that thematic role
preferences reflect a focusing on the consequences of the represented
event. Sentence continuation tasks were used in which subjects wrote
continuations to sentence fragments containing two antecedents, each
occupying a different thematic role. The results of experiments one and
two showed a preference for referring to a particular thematic role
regardless of the presence or absence of a pronoun at the start of the
continuation and regardless of whether the continuation was part of a
different sentence from the one containing the antecedents (experiment
one) or part of the same sentence (experiment two). These preferences
were interpreted as being due to a focus on the consequences of the
represented event in a mental model of the sentence. Experiment three
tested this interpretation by using sentence fragments that ended in so
(a connective that reinforces the focus on consequences) or because (a
connective that conflicts with the focus on consequences). The results
confirmed the interpretation: the observed preferences were maintained
with so but modified by because. The results are discussed in terms of
the structure of represented events, top-down and bottom-up processes,
and thematic hierarchies. The first mention effect in pronoun
comprehension is also discussed.
(August 1994; 29 pages)
Ref. No. HCRC/RP-54 Price: UKL 1.20
Enric Vallduví
Polarity items, n-words, and minimizers in Catalan and Spanish
Catalan minimizers (expressions denoting some minimal quantity or
extent) contain an overt negative marker. On the one hand, when subject
to a number of diagnostic tests, the behaviour of these minimizers
contrasts completely with the behaviour of (negative) polarity items. On
the other, minimizers generally behave like n-words (items which appear
to have a dual negative/polar nature), except in non-negative
polarity-licensing contexts. In these contexts n-words behave like
polarity items and minimizers, as noted, never do. This article argues
that Catalan minimizers, rather than n-words, instantiate the true
behaviour of negative-concord terms. The fact that n-words may appear in
nonnegative polar contexts should not be taken as typical of
negative-concord terms but rather as an exceptional phenomenon. As for
Spanish, it posesses two classes of minimizers. One class is identical
to the Catalan type. The other displays the behaviour of true polarity
items. The facts argue against identifying negative-concord terms with
true polarity items, and, therefore, against subsuming negative concord
under polarity licensing.
(August 1994; 29 pages)
Ref. No. HCRC/RP-55 Price: UKL 1.20
Richard Shillcock and Paul Cairns
Neglect dyslexia and the neuropsychology of reading: a connectionist
model of neglect dyslexia with no attentional component
Neuropsychological evidence suggests that the fovea's projections are
split precisely between the two hemispheres. This splitting means that
a word that is directly fixated in normal reading is initially divided
between the two hemispheres. We review the central data relevant to
neglect dyslexia. Recent accounts of neglect dyslexia involve either
the impairment of prelexical and lexical representations, or the
interaction between lexical representations and impaired attentional
processes over those representations. We describe a connectionist
model of neglect dyslexia which embodies the splitting of projections
from the fovea. The model captures the central features of neglect
dyslexia without requiring an attentional component.
(July 1994; 9 pages)
Ref. No. HCRC/RP-56 Price: UKL 0.70
Rosemary J. Stevenson and Agnieszka Urbanowicz
The Effects of Sentence Subject, Initial Mention and Pragmatic
Plausibility on the Accessibility of a Pronoun's Antecedents
Two experiments showed that the accessibility of a discourse entity is
jointly affected by the local salience of the antecedent and by two
aspects of the discourse structure: the pragmatic plausibility of the
interpretation of the clause containing the pronoun and the presence
or absence of prior context. Subjects read target sentences
containing two clauses. The first mentioned two individuals, while
the second contained a pronoun that referred to one of the
individuals. Cleft constructions were used in the first clause so
that two local signals to salience, subjecthood and initial mention,
could be disentangled. When the clefted individual was the subject,
then subjecthood coincided with initial mention but when it was the
non-subject, subjecthood and initial mention conflicted. The content
of the second clause either biased the interpretation of the pronoun
to refer to the subject or the non-subject of the first clause or
there was no bias. Context sentences preceded the target sentence in
Experiment 1, while the targets were presented in isolation in
Experiment 2. Results showed that local salience, pragmatic bias, and
discourse context all affected the pronoun assignment preferences and
the time taken to read the clause containing the pronoun. We suggest,
therefore, that models of discourse processing need to take account of
how local salience and global discourse structure are integrated
during comprehension.
(November 1994; 29 pages)
Ref. No. HCRC/RP-58 Price: UKL 1.20
Corin Gurr
Supporting Formal Reasoning for Safety Critical Systems
Formal methods can significantly assist in the design and modelling of
safety-critical systems. However, formal methods are frequently
criticised as being unusable through being too complex and requiring
expert knowledge to use. We assert that to make formal methods usable
they must be able to be presented in a manner which is readily
interpretable. However, we must ensure that the inferences which may
be drawn from such a presentation are correct with respect to the
formal semantics.
Concurrent systems in which communication occurs between asynchronously
operating agents are widely used in safety-critical applications.
Unfortunately designing and understanding such systems is made
difficult by the interactions between the various concurrent agents.
We present an exercise in the specification and modelling of a
safety-critical multiprocessing system fragment. This serves to
illustrate three issues which are crucial to the design and modelling of
a safety-critical system. These are the advantage of a formal approach,
particularly for concurrent systems, the importance of ensuring that a
formal model correctly represents the real system and the need to
provide a user with a clear understanding (or {\em
visualisation}) of the formal model. For this latter point we
propose, with examples, the efficacy of a well-founded graphical
representation in supporting such an understanding.
(August 1994; 13 pages)
Ref. No. HCRC/RP-59 Price: UKL 0.70
Jasper Taylor
Using Hierarchical Autoepistemic Logic to Model Beliefs in Dialogue
The study of beliefs in dialogue has proceeded along two separate
lines: the creation of logical formalisms which capture the inferences
that it seems reasonable for agents to make, and the construction of
implemented models that approximate what agents actually do. In our
project to connect the two approaches we have created a belief model
based on a reason maintenance system, and here we present a theory in
nonmonotonic logic which describes the behaviour of this model.
We start out by examining the consequences of combining the use of modal
operators (to represent nested beliefs) with autoepistemic operators (as
a means of nonmonotonic inference). We then look at how some general
principles of belief modelling can be represented, such as the
persistence and ascription of beliefs, before applying our findings to
the construction of a theory for the specific domain in which we are
interested. We present a worked example of a dialogue in this domain,
and outline the restrictions on the inferences sanctioned by the theory.
Although the purpose of the logic-based theory is merely to illustrate
the principles behind the inferences made by the implemented model, we
describe ways in which an implemented model can be created directly from
the theory by the use of a theorem prover, either an off-the-shelf
system or one specifically designed for this logic. Finally we look at
the extentions that would need to be made to the theory in order to
model further inferences available to human agents that can be made in
our chosen domain.
(November 1994; 32 pages)
Ref. No. HCRC/RP-60 Price: UKL 1.30
Keith Stenning, Robert Inder and Irene Neilson
Applying semantic concepts to analysing media and modalities
Our long term goal is an understanding of human communication in terms
which would provide the basis for rational design of information
presentations. The kernel will be a theory of the cognitive consequences
of allocating the same information to different media and modalities,
based on the user's information processing characterised in
computational terms.
Our theory information allocation starts from an analysis of differences
in logical expressiveness of graphical and linguistic representations
(Stenning \& Oberlander (1994, in press)). \nocite{stenning oberlander
theory article} \nocite{stenning oberlander barnden} This semantic
approach requires conceptualisations of {\it medium} and {\it modality}
that can be related to representation systems. We propose that media
are the physical or perceptual aspects of representations; modalities
are classes of interpretation function which map media onto meanings.
These interpretations of the terms contrast with existing HCI usage.
Graphical modalities are distinguished from sentential languages by the
nature of their interpretation functions. A hierarchy of expressiveness
of interpretations of graphics is defined, and compared with
interpretations of sentential languages. Using the expressiveness of
representations to predict their cognitive properties also requires
reference to the availability of constraints of their interpretation to
users. Further contrasts between graphics and language emerge in the
availability of their constraints.
Three example domains of graphical representations are analysed from
this perspective---matrix graphics; logic diagrams; and semantic
networks. Some empirical evidence of the usability of these notations is
reviewed as evidence that the proposed conceptualisation offers powerful
generalisations.
(December 1994; 34 pages)
Ref. No. HCRC/RP-61 Price: UKL 1.30
Francis Corblin
Multiple negation processing
This paper considers negative triggers (negative and negative
quantifiers) and the interpretation of simple sentences containing more
than one occurrence of those items (multiple negation sentences). In the
most typical interpretations those sentences have more negative
expressions than negations in their semantic representation. It is first
shown that this compositionality problem remains in current
approaches. A principled algorithm for deriving the representation of
sentences with multiple negative quantifiers in a DRT framework (Kamp
and Reyle, 1993) is then introduced. The algorithm is under the control
of an on-line check-in, keeping the complexity of negation
auto-embedding below a threshold of complexity. This mechanisn is seen
as a competence limitation imposing (and licensing) the "abrogation of
compositionality" (May 1989) observed in the so-called negative concord
readings (Labov 1972, Zanuttini 1991, Ladusaw 1992). A solution to the
compositionality problem is thus proposed, which is based on a control
of the processing input motivated by a limitation of the processing
mechanism itself.
(November 1994; 32 pages)
Ref. No. HCRC/RP-62 Price: UKL 1.30
Robert Inder and Jon Oberlander
Applying Discourse Theory to aid Hypertext Navigation
We discuss ways of improving navigation facilities in hypertext
systems, considering theoretical and implementation issues, from a
natural language processing research perspective. The key claim is
that certain ideas from the theory of discourse structure can be
exploited to improve the context-sensitivity of navigation facilities.
In particular, (i) after a node is reached by a jump, links to other
nodes can by dynamically suppressed where these are rendered
irrelevant by the user's mode of arrival; and (ii) at any point after
a jump (or sequence of jumps), the user can easily return to a limited
set of structurally accessible nodes. The approach therefore combines
certain advantages of navigation based on document structure with
those based on individual interaction histories. The ideas have been
tested by altering the implementation of \info, the hypertextual help
system built into the \emacs\ text editor, which runs on Unix,
Macintosh and {\sc pc} systems. Evaluation studies are currently
being planned, and we see further potential for exploiting notions
from discourse structure to inform the design of navigation aids.
(December 1994; 12 pages)
Ref. No. HCRC/RP-64 Price: UKL 0.70