Verb agreement in sign languages has characteristics very different from those of syntactic agreement in spoken languages. Those characteristics can be shown to follow from an Optimality Theoretic system with a constraint against overt syllables and the lexicon with under-specification. The constraint is a realization of a universal tendency in natural language to reduce articulation efforts, and its high ranking in sign languages is due to the well-known fact that sign syllables take more time to articulate than syllables in spoken languages. The analysis predicts that in language acquisition, verb agreement should arise once children have become fluent in signing and capable of phonological computation based on universal constraints ranked appropriately for sign languages. It also predicts that the existence of children with such abilities are the necessary and sufficient conditions for emergence of verb agreement in newly-born sign languages.