The sensitivity and specificity of a diagnostic test of sequence-space synesthesia

People with sequence-space synaesthesia (SSS) report stable visuo-spatial forms corresponding to numbers, days and months (amongst others). This type of synaesthesia has intrigued scientists for over 130 years but the lack of an agreed upon tool for assessing it has held back research on this phenomenon. The present study builds on previous tests by measuring the consistency of spatial locations that is known to discriminate controls from synaesthetes. We document, for the first time, the sensitivity and specificity of such a test and suggest a diagnostic cut-off point for discriminating between the groups based on the area bounded by different placement attempts with the same item.