Vowel raising in Basaa: a synchronic chain shift

Like many of the zone A Bantu languages of western equatorial Africa, Basaa, which is spoken over a large area to the north-east and east of Douala, Cameroon, shows an inventory of seven surface vowels (Guthrie 1953). The Basaa forms cited in this article, all of which are found in the comprehensive Dictionnaire Basaa-Français (Lemb & de Gastines 1973), are transcribed using the vowel symbols in (1): These vowel symbols differ from those used by Guthrie only in that the hooks are eliminated from underneath his [i] and [u] and the dots are eliminated from underneath his [???] and [???]. I assume for these vowels the characteristics indicated in (1), where non-parenthesised feature specifications are a property of surface phonological representation and parenthesised feature specifications are default phonetic values. Following Hyman's (1988) analysis of Esimbi, another Cameroonian language containing these vowels in its inventory, I take [E] and [ɔ] to be low. The verb roots in (2) contain instances of each of the seven surface vowels of Basaa: Though bare verb roots may surface unsuffixed, suffixal extensions may also be added to give applied, passive, habitual, direct causative, indirect causative, simultaneous, associative, possessive, reversive, reflexive, stative and nominalised forms. Of interest to us is the vowel raising induced within the verb root when certain of these suffixal extensions are added. In (3) we see the CVC verb forms of (2) along with their corresponding applied and indirect causative forms: Other suffixal extensions that induce raising are the passive, direct causative, simultaneous, reversive and stative extensions. For example, these other suffixal extensions attach to /ten/, one of the verb roots in (3), to give [tina], [tinis], [tinha], [tinil] and [tiní], respectively.