The study examines the grammaticalization of the noun ‘head’ in four Chadic languages: Pero (West Chadic), Mina, Wandala, (Central Chadic) and Lele (East Chadic). The study examines the grammaticalization of the following functions: spatial relation ‘on’; coreferentiality; and the point of view of the affected subject, whose manifestations are sometimes referred to as ‘middle’. The study addresses the question of motivation for grammaticalization, and in particular the fundamental question of why some functions are grammaticalized in some languages but not in others. The study rejects general cognitive processes and creativity as motivations for cross-linguistic differences in grammaticalization. The study also shows that cultural characteristics cannot explain differences in grammaticalization of the point of view of affected subject, as such differences are found among speakers who share the same culture and live in the same geographical area. Instead, the study demonstrates that language-internal factors are the motivation for the grammaticalization of the point of view of the affected subject: If the point of view of the affected subject is the inherent characteristic of some verbs in a language, the language does not grammaticalize additional means of marking this function.