<OT> New Posting: ROA-620

[roa at ruccs.rutgers.edu]

ROA 620-1003

Using phonotactics to learn phonological alternations

Bruce Tesar <tesar at ruccs.rutgers.edu>
Alan Prince <prince at ruccs.rutgers.edu>

Direct link: http://roa.rutgers.edu/view.php3?roa=620


Abstract:
A well-known formal challenge in the learning of linguistic
systems is interdependence. The problem posed to learners
by the interdependence of a phonological mapping and a correspond
ing lexicon is nontrivial. If the final consonant of a root
(preceded by a vowel) is voiceless in isolation, but voiced
when followed by a vowel-initial suffix, is the alternation
due to the syllable-final devoicing of an underlyingly voiced
consonant, or due to the intervocalic voicing of an underlyingly
unvoiced consonant? The selection of the underlying form
is dependent on the selected phonological mapping, and vice-versa
.

Many phonological alternations are motivated by the enforcement
of phonotactic restrictions. This linguistic observation
leads to a learning proposal in which the learner deals
with the interdependence of mapping and lexicon by getting
a phonotactic-based initial estimate of the mapping, without
reference to alternations or more abstract underlying forms.
This phonotactic mapping can then be used as the starting
point in a process of further refinement of both underlying
forms and mappings.

The learner can get an initial estimate to the mapping of
the language via early phonotactic learning, during which
each word is treated as if it were a monomorphemic whole.
This can be accomplished by an algorithm called Biased Constraint
Demotion (BCD). BCD learns an Optimality-theoretic constraint
ranking in response to phonological surface forms of words.
In particular, it attempts to learn the most restrictive
such ranking, resulting in a mapping which enforces all
the phonotactic restrictions realizable by the constraint
system which are attested in the data.

Later, when the learner becomes "morphologically aware",
and detects that a morpheme alternates, it can gain insight
into the correct underlying form for the morpheme by trying,
for each word containing the morpheme, underlying forms
differing in the values of precisely those features that
differ in the surface realizations of the morpheme. In this
way, the learner can determine which surface variants result
from general phonotactic restrictions, and it can then base
its stored underlying form on the surface variants that
are not fully accounted for by phonotactics (i.e., that
depend on the underlying specification).

Comments: 
Keywords: phonotactics, voicing
Areas: Learnability,Phonology
Type: Manuscript

Direct link: http://roa.rutgers.edu/view.php3?roa=620