Linguistic synesthesia is metaphorical: Evidence from the directionality of Mandarin synaesthesia

Linguistic synesthesia is the cross-linguistic usage of lexical items used in one sensory modality to describe perceptions in another (Ullmann 1957; Williams 1976; Viberg 1983). Examples include sweet voice in English and 暖色 nuan3 se4 "warm color" in Mandarin. There are three different assumptions on the nature of linguistic synesthesia, including (1) a metaphorical view (e.g., Shen 1997; Strik Lievers 2017), (2) a neurological view (e.g., Rakova 2003; Ronga et al. 2012), and (3) a literal view (e.g., Winter 2019a; Winter 2019b). This study seeks to clarify the nature of linguistic synesthesia by systematically testing the three different accounts for linguistic synesthesia in the literature. Based on the distribution and tendencies of linguistic synesthesia in Mandarin (Zhao et al., 2019), we find that linguistic synesthesia shows different characteristics from neurological synesthesia on the distribution, directionality constraints, and underlying mechanisms. However, linguistic synesthesia shares the same tendencies and properties with conceptual metaphors. Crucially, we show that most previous literature arguing for a non-metaphor analysis of linguistic synesthesia treated the aggregation of all possible mappings between two sense modalities even though each mapping could involve very different concepts from each domain. However, when each sense modality is treated as a conceptual domain that contains a set of concepts as candidates for sources and targets of different mappings constrained by mapping principles (Ahrens 2002, 2010), linguistic synesthetic mappings and conceptual metaphoric mappings have very similar behaviors. In sum, our study supports the metaphorical nature of linguistic synesthesia and a mapping principle constrained view of Conceptual Metaphor Theory.