An Open-Source Synesthesia Consistency Test for Use on the Qualtrics Platform.

Synesthesia is a neurological phenomenon in which healthy individuals experience additional, automatic, and consistent perceptions unrelated to veridical sensory input. For most of the most common forms of synesthesia, the additional sensation is a color: grapheme-color synesthetes experience specific letters of the alphabet as having specific colors, tone-color synesthetes experience specific sounds as having specific colors, etc. The “gold standard” method to diagnose X-to-color synesthesia is to measure test-retest consistency: synesthetes use a colorpicker to choose the color they experience for a particular stimulus, and then are retested minutes, months, or even years later; genuine synesthetes experience highly consistent associations across time. There is not currently an open source tool to collect color associations from synesthetes. In addition to presenting a technical barrier for entry into synesthesia research, the lack of an open source standard has also led to a proliferation of (slightly) different choices in methodology from lab to lab. In the present work, I use colorpicker experiments in synesthetes and controls to demonstrate that even small methodological details in test-retest experiments can profoundly influence the resulting data. I use this data to generate an online color picker with ideal experimental properties. The colorpicker is open source (available on a Github repository) and can be implemented by anyone with an account on the Qualtrics platform, one of the most common online experimental platforms in the world.