The MULTISENSE test of lexical-gustatory synaesthesia: an automated online diagnostic

Lexical–gustatory (LG) synesthesia is an intriguing neurological condition in which individuals experience phantom tastes when hearing, speaking, reading, or thinking about words. For example, the word “society” might flood the mouth of an LG synesthete with the flavor of fried onion. The condition is usually verified in individuals by obtaining verbal descriptions of their word–flavor associations on more than one occasion, separated by several months. Their flavor associations are significantly more consistent over time than are those of controls (who are asked to invent associations by intuition and to recall them from memory). Although this test reliably dissociates synesthetes from nonsynesthetes, it suffers from practical and methodological limitations. Here we present a novel, automated, online consistency test, which can be administered in just 30 min in order to instantly and objectively verify LG synesthesia. We present data from two versions of our diagnostic test, in which synesthetes report their synesthetic flavors either from a hierarchical set of food categories (Exp. 1) or by specifying their basic component tastes (sweet, salty, bitter, etc.). We tested the largest sample of self-declared LG synesthetes studied to date and used receiver operating characteristic analysis to assess the discriminant power of our tests. Although both our methods discriminated synesthetes from controls, our second test (Exp. 2) has greater discriminatory power with a threshold cutoff. We suggest that our novel diagnostic for LG synesthesia has unprecedented benefits in its automated and objective scoring, its ease of use for participants and researchers, its short testing time, and its online platform.