Meaning or morphology: Individual differences in the categorization of Kinyarwanda nouns

Unlike the gender-based systems of noun categorization in many European languages, numerous semantic categories contribute to Bantu noun class systems. Kinyarwanda, the focus of our study, has a rich inventory of noun class prefixes, but it is unknown to what degree the semantic and morphological systems underlying these noun classes influence how speakers mentally categorize nominals in their language. To investigate this, speakers of Kinyarwanda (n = 46) were recruited to take part in an online triadic comparison experiment. Across 144 trials, participants were asked to identify the item most different from a written list of three nouns. These lists were constructed based on morphological similarity (from noun classes 3, 5, 7, or 9), semantic overlap (from the domains of ‘mammals’ and ‘tools’), or both. Results show an overall preference for semantic grouping in the triads, although the strength of these preferences differed across individuals. This variation turned out to be systematic and predictable: speakers of Kinyarwanda who spoke Kiswahili as an additional language generally preferred categorizing on the basis of noun class, while those who did not speak Kiswahili as an additional language were more likely to base their decisions on the shared semantic domains of the nouns. These data suggest that noun categorization choices in Kinyarwanda can be influenced by knowledge of other linguistic systems, highlighting the impact that learning additional languages may have on first-language lexical knowledge.