1 OCP Effects in Optimality Theory Scott Myers University Of Texas May 10, 1994 (e-mail: lign102@utxvms.cc.utexas.edu) 1. A Problem in Autosegmental Phonology One of the central constraints on autosegmental representations is the Obligatory Contour Principle (Leben 1973, 1978; McCarthy 1986). (1) Obligatory Contour Principle (OCP) At the melodic level, adjacent identical elements are prohibited. In the domain of tone, for example, the OCP rules out representations such as that in (2): (2) *H H | | s s Three different effects have been attributed to the OCP. First, it has been interpreted as a morpheme structure constraint. According to this interpretation, no morpheme can have a violation of the OCP, e.g. (2), as part of its underlying representation. Thus a sequence of high toned syllables within a morpheme must be represented underlyingly with a single multiply linked high tone, and never with two high tones as in (2). Considerable evidence has accumulated in favor of this interpretation: Leben (1973), McCarthy (1986), Hyman (1987), Kenstowicz and Kidda (1987), Myers (1987). Second, the OCP has been interpreted as a derivational constraint in the sense of Kisseberth (1970). According to this interpretation, the application of a phonological rule is blocked if it would create a violation of the OCP. In Shona, for example, a high tone spreads onto a following toneless syllable, as illustrated in (3a). This spread is blocked, however, if the syllable following that toneless syllable is also high, as in (3b,c). Application in that case would create an instance of (2), a violation of the OCP.