The contribution of full tone marking to oral reading fluency and comprehension in Yoruba and Ife


 Orthographic depth is a key concept in literacy acquisition and can be measured separately for completeness, simplicity and
 consistency. The first of these is pertinent to discussions about whether tone should be marked in African
 orthographies, because a zero tone representation is relatively incomplete and deep whereas a full tone orthography is relatively
 complete and shallow. We undertook a series of literacy experiments in ten Niger-Congo languages to test the extent to which full
 tone marking contributes to reading and writing skills. In a within-subject design that closely follows Bird (1999b), participants orally read two full tone and two zero tone texts and also added tone accents
 to unmarked versions of two of the texts. Speed, accuracy, comprehension, as well as a range of linguistic, ethno-literacy,
 demographic and L2 literacy variables were tracked. The present article narrows the scope of the wider research project (Roberts & Walter 2021) to two of the languages, Yoruba and Ife, which are
 linguistically similar, yet have highly dissimilar results. In Yoruba, full tone marking does not contribute to any improvement in
 reading measurements, and tone writing skills are generally poor. In Ife, on the other hand, full tone marking contributes to
 speed, accuracy and comprehension, and tone writing is the most accurate of all the languages. The results suggest that the social
 profile of the participant and the ethno-literacy profile of the language community are more predictive of reading and writing
 performance than is the linguistic profile of the language.