Fig. 8.

Receiver operating characteristic (ROC) curve showing the trade-off between sensitivity and specificity of the 5-Tastes task in predicting self-declared synesthesia, at different cutoff values (curved line). The straight diagonal line represents a test with no discriminant power (i.e., that classifies scores at guessing rate), for comparison. Dots represent sensitivity and one-specificity values for each R-square score. The optimal cutoff value is defined as the point that results in the highest true positive rate (i.e., is highest on the vertical axis) and the lowest false positive rate (horizontal axis). The area under the curve represents the discriminant power of the test