Does marking tone make tone languages easier to read?

Among designers of orthographies for previously nonwritten languages, the prevailing wisdom is that native speakers of tone languages need to see at least some tones marked to achieve full literacy in those languages. A counter argument is that marking tone confuses native speakers of tone languages. We report here on an experiment on tone marking in Kom, a language of the Grassfields region of Cameroon. The results show that, for Kom at least, tone marking makes written sentences harder to figure out initially, harder to say, and harder to say correctly. Comparative research using refinements of the methodology described here will help us answer important questions, like whether or not these effects vary with the number of tones in a language or with the linguistic function of tones. The knowledge gained from comparative experiments will help speakers of the world's nonliterary languages achieve popular literacy in those languages. Popular literacy, we argue, is one of a small number of things that promotes the survival of language diversity.