<OT> New Posting: ROA-695

[roa at ruccs.rutgers.edu]

ROA 695-1104

Contrast Analysis in Phonological Learning

Bruce Tesar <tesar at rutgers.edu>

Direct link: http://roa.rutgers.edu/view.php3?roa=695


Abstract:
This paper presents a specific proposal for the use of observatio
ns about surface contrasts in the learning of underlying
forms for morphemes, and investigates the strengths and
weaknesses of that proposal. The main formal result presented
here is that, if a set of assumptions are satisfied by the
grammatical system, then whenever two distinct morphemes
contrast on the surface in a particular environment, at
least one of the underlying features on which the two differ
must be realized faithfully in each of the morphemes in
that environment. To put it another way, at least one of
the surface features distinguishing the two surface realizations
must faithfully reflect a distinction between the underlying
forms of the two morphemes. This property is called the
Faithful Contrastive Feature property.

The significance of this property is that at least one contrast-
causing feature must be overt, in the sense that its underlying
values are faithfully presented in the surface forms, where
the learner can observe them.  This result forms the basis
for an algorithm, Contrast Analysis, which starts with a
number of features in underlying forms unset (not yet specified),
and specifies them for a morpheme only when that morpheme
contrasts with another morpheme, and the contrast can only
be attributed to a single unset feature. Because the contrast-
causing feature must be faithfully realized, the learner can
set that feature in the underlying form of each morpheme
to match its surface realization for that morpheme.

The contribution of Contrast Analysis will emerge in its
role in a larger theory of language learning. We illustrate
Contrast Analysis by using it as part of a procedure for
initial lexicon construction, designed to construct a working
lexicon for use by a subsequent procedure for jointly learning
the lexicon and the phonological mapping (a constraint ranking).
Initial lexicon construction depends solely on morphologically
analyzed surface forms, and does not make reference to phonological 
mappings. Initial lexicon construction cannot determine
all feature values for underlying forms in all cases. In
fact, it is likely that in complex cases it will be unable
to set a significant number of values for many underlying
forms. If common beliefs about the close interrelation between
underlying forms and grammatical mappings are correct, it
is not possible in general to determine all underlying forms
for the morphemes of a language independent of consideration
of the grammatical mapping for the language. However, using
Contrast Analysis in initial lexicon construction does offer
the possibility of setting the values of some features in
some morphemes early on. Those values, in turn, could do
much to constrain the search involved in subsequent processes
of inferring both the mapping and the rest of the underlying
forms. Further, Contrast Analysis is defined such that it
could be invoked at several points during learning, opening
the possibility that it could be invoked during the joint
learning of the lexicon and the phonological mapping.

Comments: 
Keywords: learnability, phonology, contrast, underlying forms
Areas: Phonology,Learnability
Type: Manuscript

Direct link: http://roa.rutgers.edu/view.php3?roa=695