Stress is the Trigger of Chamorro Umlaut

An adequate account of umlaut must explain why unstressed vowels are not viable targets for umlaut, and, alternatively, why umlaut cannot spread through these unstressed vowels to reach the stressed vowel (*i pilénnun, *i mindéŋgu). The attested behavior is unexpected from the point of view of Positional Faithfulness (Beckman, 1999) because weak (unstressed) positions block spreading while strong (stressed) positions permit it. These data seem to call for ―reverse‖ Positional Faithfulness constraints that preferentially protect unstressed syllables. Second, umlaut may optionally target a certain kind of secondary stress: