Inducing Synesthesia in Non-Synesthetes: Short-Term Visual Deprivation Facilitates Auditory-Evoked Visual Percepts

Non-synesthetic participants sat upright in a dark environment with their eyes closed for about 30 minutes. After an initial five minutes of dark adaptation, they completed an auditory visual-imagery task and reported whenever a sound evoked a visual percept.

• ▸After roughly five minutes of visual deprivation, sounds evoked synesthesia-like visual percepts — vivid colors and Klüver form-constants — in about half (~50%) of non-synesthetes.
• ▸These auditory-evoked visual experiences appeared in a matter of minutes, not years, showing how quickly latent cross-sensory pathways can surface.
• ▸The results challenge the view that conscious sound→vision crossover is exclusive to congenital synesthetes.

It shows the auditory→visual wiring for 'seeing sound' already exists in most brains and can be coaxed out fast. Training a focused, low-distraction listening state — like the deep-focus phase in Chromesthesia — helps those latent pathways surface.