Developing a Theoretical Framework for Yoruba Linguistic Relativity: Evidence from Spatial Cognition and Tonal Categorisation

Linguistic relativity theory posits that structural properties of a language influence non-linguistic cognition, yet empirical testing of this hypothesis has focused predominantly on Indo-European languages, leaving tonal and agglutinative African languages significantly underrepresented. This study develops an original theoretical framework for Yoruba linguistic relativity, drawing on experimental evidence from spatial cognition and tonal categorisation tasks conducted with adult Yoruba speakers in Oyo State, South West Nigeria, and a matched English-dominant control group. Using a multi-method experimental design combining psycholinguistic tasks, neuroimaging-compatible behavioural measures, and computational modelling, the study tests whether Yoruba tonal categories and spatial relational vocabulary shape non-verbal cognitive performance in tonal and spatial discrimination tasks. The theoretical framework integrates Sapir-Whorf legacy theory with contemporary neo-Whorfian cognitive science, colour and space categorisation research, and cross-linguistic cognitive typology. Existing Yoruba psycholinguistic research has focused on sentence processing and word recognition, with cognitive relativity effects being entirely unexplored as a research programme. This dissertation makes an original theoretical and empirical contribution by establishing Yoruba as a test case for linguistic relativity theory in tonal and spatial domains. Findings are expected to demonstrate selective relativity effects in spatial but not tonal categorisation, challenging universalist assumptions about tonal language cognition. Recommendations will address a multi-site collaborative research programme for Yoruba psycholinguistics and the development of Yoruba-specific experimental stimulus materials. Keywords: linguistic relativity, Yoruba, spatial cognition, tonal categorisation, psycholinguistics.