The purpose of this report is to contribute to formal 
 learning theory in Optimality Theory by providing an 
 analysis of the problem posed by covert phonological 
 interaction. Building on standard theories of syllable 
 structure and metrical stress, we analyze a typological 
 system in which regular processes of epenthesis interact 
 in non-transparent ways with metrical stress. The nature 
 of this interaction, which implies several complex 
 learning decisions, is shown to support the following 
 conclusions relevant to general mechanisms of language 
 learning: 



1. A process of lexical acquisition in which surface 
 phonological structure is directly incorporated into 
 the lexicon (sometimes called 'the identity map') leads 
 to a state in which the learner is committed to a grammar 
 that over-generates.



2. Acquisition of some aspects of a lexical representation
 (LR) may take place in the absence of morpho-phonemic 
 alternations; acquisition of LRs that are not identical 
 to the surface form is necessary to solve the over-
 generation problem.



3. Over-generation problems may arise in learning from 
 constraint interactions that are distinct from those that 
 exist among faithfulness constraints that stand in a 
 special/general relation.