Iconicity of tonal disharmony in expressing the distinguishability of otherwise identical elements

We present evidence that iconic phonotactics can motivate phonological alternations by examining some patterns of grammatical tone in Igbo, Nigerian Pidgin and Yorùbá. In the languages, plurality of an event or entity can be expressed by reduplicating ideophones (e.g., [bàm̀bà] ‘very big’ vs. [bàm̀bà-bàm̀bà] ‘multiple big things’ in Yorùbá). To express that an event or one of its subcomponents is distinguishable from an otherwise identical event along a specific dimension, the reduplicant and the ideophonic base undergo tonal alternation, resulting in tonal dissimilarity between the base and reduplicant (e.g., [bàm̀bà-bamba] ‘distinguishably big’ in Yorùbá). We propose that the tonal alternation in each language is triggered by a morpheme with only tone melody as its exponent. The fact that the corresponding base–reduplicant syllables bear opposite tone values constitutes a pattern of disharmony, which is a requirement for adjacent phonological elements to have dissimilar features. The form–meaning association of the tonal alternations is consistent with the iconicity of ablaut and rhyming reduplication across languages. We explore the implications of the iconic patterns for the hypothesis that disharmony is perceptually motivated, as adjacent dissimilar elements are easier to distinguish. Other implications of the pattern are also discussed.