For most people, looking at a painting is a purely visual experience. Enjoyable. Meaningful. Beautiful. It starts with the eyes and ambient light. Outside the gallery, glancing at a rose blossom recruits multiple senses, each of which arise from differently attuned sense receptors. Your eyes see. Your nose discriminates smells. The touch receptors in your skin discern textures. About 95% of us experience the world this way.
But that characterization is about to change. A recent study suggests that one kind of synesthesia alone could upend the orthodox understanding of conventional perception. Just as an–esthesia means “no sensation,” syn–esthesia means “coupled sensation” (the British spell it synaesthesia). One in 90 among us exhibits some form of overt synesthesia, while even more people, 1 in 23, carry the genes for the hereditary trait.
One synesthete may see indigo when thinking of the weekday Wednesday, whereas another might taste oranges when they handle something cold. Some 4% of adults experience synesthetically cross–coupled sensations. But if the above study holds true, that number may be low because science currently focuses only on the most outwardly visible types of synesthesia. Many of us could be experiencing a form of it subtle enough that we don’t even notice.
Some 20% of participants in a study published in Consciousness and Cognition “heard motion,” mean ing an internal sound in response to a moving visual stimulus.  The phenomenon occurred while participants completed two tasks designed to assess their ability to distinguish sounds from fine visual movement while they were distracted.
Participants first had to match pairs of visually presented Morse code–like patterns. As they watched these patterns flash by on a screen, 22% said that they heard sounds congruent with the visual patterns even though no sounds actually accompanied them. These participants matched patterns more accurately than controls.
Try this at home. Watch this video a few times in a quiet room with the sound off. Then close your eyes and try to recall them. Do you hear sounds that correspond with the pattern? Let me know how your experiment goes in the comments.
Secondly, participants were asked to detect faint sounds while simultaneously watching visual patterns that were mismatched to the sound. Those who did better on the first task performed poorly on the latter one. They found the light flashes distracting and confusing, meaning that the ability to hear visually-evoked sounds must be sufficiently real as to interfere with the ability to detect actual ambient sounds.
Remember that the ability in the study group was five times greater than the frequency of synesthesia in the general population. The study’s lead scientist suggested that when the brain re-codes visual signals as sounds, it gives participants additional information that makes the sound patterns easier to track and recall. That in itself is impressive. 
Sound and sight are already so strongly linked that we routinely believe that cinema dialogue comes from the mouths on screen rather than the surrounding speakers. This naturally occurring illusion may account for the high prevalence of hearing motion in the study group. Everyday movement is so often accompanied by intrinsic sounds—think of a car whooshing by or the whir of fan blades—that any noise created by your s brain would be drowned out. 
Because hearing motion is subtle the ability might seem mundane. But think about the appeal of strobe lights at concerts. Synesthetically herd flashes would add a new depth of sound coming from the loudspeakers. Live dance music would sound altogether different from a recording of the same music. A flickering candle would produce its unique romantic hum. All of us may have been enjoying a subtle synesthesia all along.
Perception may be due for a redefinition. Our eyes see, yes, but vision can apparently also hear. Tactile receptors can also taste. If synesthesia research continues this way we may find that we all have a little bit of it in us. My Ted–Ed lesson talks about this: