Ask a chromesthete for the color of forty sounds, wait six months, and ask again. Genuine synesthetes land startlingly close to their first answers; controls asked to invent and memorize pairings drift badly, even when offered money to fake it well. That gap is the field’s ground truth.
Consistency scores are usually computed as color distance between sessions, which turns a subjective report into a measurable quantity. The method’s logic is simple: imagination varies, perception repeats.
Any serious synesthesia test is built on this principle, including the batteries used in research. Quizzes that skip it are measuring enthusiasm.