Aristotle's five outward wits defined the five senses: touch, taste, smell, sight and hearing. But in the last several decades, the definitions of these senses have begun to tangle. Some researchers argue there are more than five senses, like proprioception, or an awareness of the body in space. Others argue that our senses aren’t even all that discrete, something known as synesthesia—a neurologic condition in which two or more senses mix or amplify one another. Though generally thought to be rare, a new study suggests that one particular form of this condition—hearing sounds from flashes of light—may be more common than once thought, reports Hannah Devlin for The Guardian.
In the study, recently published in the journal Consciousness and Cognition, researchers presented pairs of Morse-code like patterns to 40 volunteers, either visually or as sound. The subjects were then asked to determine whether the pairs contained the same sequences of dots and dashes. Freeman and his team then asked the participants whether they heard faint sounds when they saw the flashes.
It turns out, 22 percent of participants claimed they heard faint sounds associated with the flashing lights. Those people also did better than other participants in matching the pairs of patterns, suggesting that they had some sort of advantage during the test.
“These internal sounds seem to be perceptually real enough to interfere with the detection of externally-generated sounds,” Elliot Freeman, a cognitive neuroscientist at City University and the study’s lead author tells Devlin. “The finding that this ‘hearing-motion’ phenomenon seems to be much more prevalent compared to other synesthesias might occur due to the strength of the natural connection between sound and vision.”
Research into synesthesia has gained momentum in recent years. Scientists have found that people with the mixed senses have stronger than normal connections between parts of their brains, leading to some interesting cases. “Very common stimuli are things like days of the week or months of the year, that will have particular colors for particular synesthetes,” Stephanie Goodhew who studies synesthesia at Australian National University tells Mattew Doran at the Australian Broadcasting Corporation. “For somebody the word Tuesday might elicit the color orange, for somebody else it might be green. They're more likely to be engaged in artistic or creative pursuits, so they'll sort of be over represented among artists and writers.”
While Doran reports about one in one hundred people experience synesthesia, Freeman’s number of one in five means that a larger portion of the population may have cross-sensory moments, even if the experience is not as dramatic as tasting Wednesday. “A lot of us go around having senses that we do not even recognize,” Freeman tells Devlin.
A similar study was conducted on self-professed synesthetes in 2008, in which the volunteers reported hearing beeps, taps or whirring sound when they were shown moving or flashing lights. They too performed much better than average on pattern recognition test. Based on that study, the researchers estimated that up to one percent of the population experienced auditory synesthesia, but Freeman’s research shows that the number may be much, much higher.
While the concept of cross-sensory perception may be foreign to many people, there is one way the average person can experience the inter-tangling of sound, color, taste and smell for themselves. The British dance troupe Bitter Suite attempts to help the audience experience synesthesia. Dancers put morsels of food in audience members’ mouths during certain moments, give them a whiff of smells and also tickle them to bring other senses besides their eyes and ears into the performance.
Next time you see a flash of light, pay attention. You ears may also be part of the experience.