Review of Multidisciplinary Approaches to Language Production |
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Date: Mon, 09 May 2005 11:06:18 +0200
From: Michael Zock
Subject: Multidisciplinary Approaches to Language Production
EDITORS: Pechmann, Thomas; Habel, Christopher
TITLE: Multidisciplinary Approaches to Language Production
SERIES: Trends in Linguistics: Studies and Monographs 157
PUBLISHER: Mouton de Gruyter
YEAR: 2004
Michael Zock, Director of Research, LIMSI-CNRS (Orsay, France)
This book deals with natural language production, that is, the
translation of a communicative intention (goal) into language. While
language production may cover a wide range of phenomena (words,
sentences, text), involve different tasks (sentence or paraphrase
generation, translation) and take place in different modes, nearly all of
the the work presented in this volume is confined to the production of
spoken forms (words or sentences).
Speaking is a complex process. It involves many tasks (choice of a
topic, sentence frame and words, morphological and acoustical,
operations), various knowledge sources (encyclopedia, dictionary,
grammar), and it is carried out under severe space (memory) and time
constraints (speed). Yet people succeed amazingly well. How is this
possible? Since answering such a complex question is a gigantic
enterprise, the editors of this book have decided to convince a funding
agency (DFG) to support their quest, have nearly two dozen teams
spread all over Germany (17 universities) work on the same topic.
The book here presented summarizes the outcome of this effort, a six-
year long priority program funded by the German Research
Foundation, aiming to bring together researchers with different
backgrounds (linguistics, psychology, computer science, neuro-
science), but with a common goal: understand the cognitive processes
underlying language production. The focus of their work is on
empirical explanation (evidence) rather than on formal
representations. The unifying framework, or, the big picture within
which this work was carried out, is W. Levelt's book Speaking (Levelt,
1989), a true masterpiece.
To account for the information processing, Levelt conceives an
architecture composed of three serially ordered, relatively
autonomous main components (conceptualizer, formulator,
articulator). These modules are in charge of message generation,
grammatical encoding, phonological encoding, and articulation. In
addition there is a feedback loop: the speaker is listening to himself.
The papers of the book (17, plus a preface by the editors and an
introduction by M. Garrett, a pioneer in language generation
research) can be placed within the chart (or architecture) proposed by
Levelt.
The first two papers fall into the message planning component. The
paper by Guhe et al. (Incremental generation of interconnected
preverbal messages) deals with the conceptual preparation for
describing a scene. Since the scene is composed of various objects
(airplanes), and since the scene changes all the time, the subjects
have to decide which elements to include in their message, how to
combine the to-expressed events and how to express the message.
Hence, issues of coherence and coreference (pronouns) have to be
addressed. In addition, in order to be able to address the dynamic
aspect of the situation, planning is done incrementally.
The next paper by Gardent et al. (Generating definite descriptions,
non-incrementality, inference, and data) also deals with incrementality,
or rather, its opposite. The authors show quite convincingly some of
the shortcomings of too strict incremental processing, that is, too early
verbalization of some planned content, (here, the definite
descriptions) may yield hilariously complex sentences, whereas
delayed verbalization would have resulted in quite natural output. One
of the interesting features of this work is that it takes corpus data into
account.
The paper by Harbusch and Woch (Integrated natural language
generation with schema-tree adjoining grammars) deals with the
problem of easing integration of basically very different kind of
information, conceptual and linguistic. In order to do so, they resort to
a unification mechanism, tree adjoining grammars.
Klabunde and Glatz (On the production of focus) address the hairy
issue of focus. While intuitively clear and without any doubt important
(noun vs pronoun, active vs. passive voice), there is a lot of
disagreement when it comes to this notion. To be understandable,
discourse is embedded into a situation, hence part of the message is
old, while the other is new, or in focus. Unfortunately focussed and
new information are not always identical.
Tappe et al. (Thematic information, argument structure, and discourse
adaptation in language production) address the issue of thematic role
assignment. According to them a thematic processor is needed to
interface the conceptual and linguistic component. In other words,
they suggest adding a thematic processor to the existing
architectures.
Kempen and Harbusch (A corpus study into word order variation in
German subordinate clauses: Animacy affects linearization
independently of grammatical function assignment) resort to a corpus
analysis in order to account for word order preferences in case
languages like German. Their findings are likely to have
consequences on the generation architectures or processing
strategies. The authors suggest computing simultaneously
grammatical functions and linear order, which, in the Garrett and
Levelt model was always done serially, the former preceding the latter.
The next paper by Carroll, et al. (The language and thought debate: A
psycholinguistic approach) addresses an age old problem, which,
surprisingly has hardly ever been addressed within the framework of
language production, where it is highly relevant. Nearly all systems
are based on the assumption that the message on which the
formulator works is specific enough in order to do his job, yet,
language may have to say its word. Indeed, cross-linguistic
comparisons allow the authors to show the kind of influence a given
language may have on the preverbal message.
Leuninger, et al. (The impact of modality on language production:
Evidence from slips of the tongue and hand) study whether sign
languages obey similar rules as spoken languages. Their results
reveal amazing similarities in terms of error typology.
The next few papers clearly fall into Levelt's second component, the
formulator. Pechmann and Zerbst (Syntactic constraints on lexical
access in language production) summarize their work on lexical
access, using a well known technique the picture-word paradigm.
Their results suggest changes in the generation architecture, allowing
for cascaded rather than strict serial processing.
Blanken, et al. address similar problems (The dissolution of word
production in aphasia: Implications for normal functions). They
reach quite similar conclusions, even though their data are based on a
very different population, brain-damage people.
Schade (The benefits of local-connectionist production) also reaches
a similar conclusion, though his conclusions are based on a computer
simulation. He shows how an interactive model can handle several
problems that the Levelt model does not address at all. Two
interesting features of this approach lie in the fact that the system can
be tuned to accommodate, little by little with the empirical data. In
addition, the different models compete. Hence, instead of preferring a
model on a priori grounds, choice can be based on the result of the
competition.
The next two papers report work based on brain activity measures.
Jansma, et al. (Electrophysiological studies of speech production) use
electrophysiobiological methods to study language production, while
Dogil, et al.(Brain dynamics induced by language production) use
brain imagining tools. They provide evidence for localization effects
concerning syntax and semantics.
The next two papers deal with morphology. Boelte, et al. (Morphology
in experimental speech production research) ask whether word forms
are computed or accessed, since readily stored.
Unlike the authors of the preceding paper, who addressed three kinds
of morphological problems (derivation, inflection and compounding)
Janssen, et al. (Morphological encoding and morphological structures
in German) focus only on the processing of inflections. Noticing
important differences in terms of processing German and Dutch, they
try to find explanations in the structure of the two languages to
account for these facts.
Weingarten, et al. (Morphemes, syllables, and graphemes in written
word production) address a problem, a bit outside of the Levelt
paradigm, as it deals with written word production. Yet, it seems, that
there are some similarities between the processing of the spoken and
written word.
Finally, Hamm and Bredenkamp (Working memory and slips of the
tongue) show some of the effects that working memory has on the
(mis)functioning of the production system. Memory constraints can be
said to be responsible for certain kinds of breakdowns, or speech
impairments, like sound exchange errors.
CRITICAL EVALUATION
To launch and keep alive a project like this (raise the funding for 20
teams for 6 years) deserves respect. Also, a book on language
production from scholars with such a diversity of backgrounds is highly
appreciated, since, there are not many books of this kind. Even
though I'm not a newcomer to the field, there were many things I've
learned by reading the book, and I've found nearly all the papers of
excellent quality.
This being said, the book also has a few shortcomings. While I think
that the editors have done a fantastic job in bringing this project to life,
and while they've also done a great job as authors, I don't think that
they've succeeded equally well as editors. Here are some of the
reasons why I think so.
Lack of guidance for the reader:
(a) the table of contents is not structured, yet this would have been
quite easy to do. In the absence of such section titles, grouping the
papers of the same kind under the same heading, a newcomer will
perceive the papers just as an unordered collection of papers. The
field is so complex and wide, that without guidance the reader is likely
to get lost, or not to get the big picture.
(b) The index is done by hand. I've checked quite a few entries, each
of which was mentioned only once or twice, yet the terms occurred
more than half a dozen of times. Since papers were submitted
electronically, building an index automatically would have been quite
easy.
(c) Given the fact that all authors cast their work in Levelt's paradigm,
and since not every reader can be expected to know his book, it
would have been useful to resort to one of the following solutions: use
one of Levelt's papers describing his framework, have Levelt
contribute such a chapter, or have had it written by the editors. This
lost space could at least partially be recovered by the fact that it would
allow authors to refer to the introduction rather than having, one after
another, describe basically the same aspects of Levelt's work. This
would serve as advanced organizer, guiding the reader. Another way
of gaining back some space would be to reduce the length of some of
papers that are really very long (50-60 pages).
(d) The editors mention several workshops that have taken place
during the 6 years of the project, yet none of these discussions (what
were the problems, achievements) become in any way visible in this
volume.
References:
To ease the access of references, it would have been better to group
them all at the end of the book. This would have saved space, which
could have been used profitably for a glossary. While the diversity of
approaches is certainly stimulating, it can also be overwhelming. Not
everyone has the background to understand all the work, techniques
or terminology.
Integration of the work with other work in psychology and
computational linguistics:
While no other book matches Levelt's landmark work, there are a lot
of books than contain useful, complementary information, some in
psychology and a lot in computational linguistics (at least a dozen).
For some pointers see Bateman & Zock (2003: 301) and Zock &
Adorni (1996).
It is really surprising that the Reiter and Dale book, which in
the ''natural language generation community'' plays a similar role as
Levelt's book does in psychology is only mentioned once in this book.
Also, mentioning T. Dijkstra & K. de Smedt's (1996) book (with a
foreword by P. Levelt), would have been in point, as it tries to
accommodate work from different backgrounds in a common
framework.
Even more surprising is the fact that nothing is said about the other
community working on language production (they call their field ''text
generation''). This community, which is very dynamic, productive (it
has produced at least a dozen books over the last ten years), has a
website (http://www.siggen.org/index.html), an international
conference every year, and integrates people from many horizons (as
a matter of fact, psychologists like Kempen, Harley, Pechman and
Roelofs have presented their work in this framework).
One last point. For the newcomer it may be startling that ''natural
language production'', is confined only to sentence production. Yet,
again, there is a whole literature on this subject, both from a
computational and psycholinguistic perspective (see Andriessen et al.,
1996, de Beaugrande, 1984; Fayol, 1997; Flower & Hayes 1980).
Despite all these criticism, I maintain the respect that the editors of this
volume deserve, for the quality of the final product and the enormous
work put into the project to make it work.
REFERENCES
Andriessen J., deSmedt K. & Zock, M. (1996) Discourse Planning:
Empirical Research and Computer Models. In T. Dijkstra & K. de
Smedt (Eds). Computational Psycholinguistics: AI and Connectionist
Models of Human Language processing, London: Taylor & Francis,
pp. 247-278
Bateman, J. & Zock, M. (2003). Natural language generation. In R.
Mitkov (Ed.), The Oxford Handbook of computational linguistics.
London: Oxford University Press, pp. 284-304
de Beaugrande, R. (1984). Text production: toward a science of
composition, Norwood, New Jersey: Ablex
de Smedt, K., Horacek, H., & Zock, M. (1996). Architectures for
natural language generation: problems and perspectives. In G. Adorni
& M. Zock (Eds.), Trends in natural language generation: an artificial
intelligence perspective (pp. 17-46). New York: Springer Verlag,
Lecture Notes in Artificial Intelligence 1036
Fayol, M. (1997) Des idées au texte: psychologie cognitive de la
production verbale, orale et écrite. Paris: Presses Universitaires de
France
Flower, L. & Hayes, J. (1980). The dynamics of composing: making
plans and juggling constraints, dans: Gregg & Steinberg (1980).
Cognitive processes in writing, Hillsdale, New Jersey: Erlbaum,
Reiter, E., & Dale, R. (2000). Building natural language generation
systems. London: Cambridge University Press.
Zock, M., & Adorni, G. (1996). Introduction. In G. Adorni & M. Zock
(Eds.), Trends in natural language generation: an artificial intelligence
perspective (pp. 1-16). Heidelberg: Springer Verlag, Lecture Notes in
Artificial Intelligence 1036
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ABOUT THE REVIEWER:
ABOUT THE REVIEWER
Michael Zock holds a Ph.D. degree in experimental psychology. He is
currently research director at LIMSI-CNRS (Orsay, France). Having
launched the European Workshop on Natural Language Generation
(1987, Royaumont) he has edited several books on generation. His
major research interests lie in the building of tools to support people,
producing, or learning to produce language. His recent work is
devoted to the building of extensions to electronic dictionaries aiming
to facilitate the access, memorization and automation of words and
syntactic structures, and to overcome the tip-of-the-tongue-problem.
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