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So, there's a thing happening on the internet that you might have seen: viral gifs—or gifs, no one's decided for sure yet—that seem to have a sound. They're silent, like all gifs, but if you're one of the many people that experience a phenomenon known as vEAR, you might have heard them. vEAR stands for Visually Evoked Auditory Response.

It's only recently been identified, in a paper published in 2017. Though initially vEAR flew under the radar, it got launched into the spotlight in December of 2017 when a gif of a bouncing electrical tower went viral on Twitter. We'll stick it in the description for you to see.

According to the highly unscientific twitter poll alongside said tweet, a majority of respondents perceived sound from the gif as the tower hit the floor. That's a pretty sizeable number. Of course, there's always the possibility that a lot of people were just going along to feel included—but then again, there's whole subreddits devoted to noisy gifs.

Even so, that tweet caught the eye of a whole lot of psychology researchers, who promptly got really excited. Scientists from around the world started weighing in on possible solutions. One particular scientist from City, University of London spotted the tweet, and immediately thought it was a great real world example of work on vEAR published by his lab only a few months prior.

In that 2017 paper, published in the journal Consciousness and Cognition, the researchers looked at sensations of sound that could be evoked by flashes of light. When asked if the presentation of flashes were accompanied by a sound, 22% of their participants said yes. And then, in order to confirm those reports of perceiving sound, investigators also tested participants on a more objective measure they called ‘visual Morse codes'.

In this study, a white disk presented on a black background turned on and off in particular Morse-like patterns. The participants that reported hearing the flashes were significantly better at identifying whether pairs of Morse code flashes were the same than those who were unable to hear flashes. Those that heard the stimuli seemed to be turning the visuals into auditory information, which stores timing way better than visual information does.

Kind of like an audio cheat sheet that other participants just didn't have access to. Harnessing the power of the twitter storm, these researchers started talking to news outlets about their theory. And, at the end of articles interviewing them, many outlets provided a link to the researchers' new study investigating the phenomenon.

All in all, they got over 4000 responses from around the world about just how people experienced the supposed sounds these gifs were making. The data showed that videos depicting situations with a lot of ‘movement energy', or predicted loud sounds, like a car crash, were most likely to trigger vEAR. And, though they didn't have tests good enough to measure it directly, the researchers suggested that vEAR may be a kind of synesthesia.

Synesthesia is a crossing over of senses. When one sensory modality like hearing is stimulated, those with synesthesia might perceive something in a different, unstimulated sensory modality. They might associate certain types of music automatically and reliably with certain colours or patterns, for example.

There are a lot of different types of synesthesia. Everything from sensing particular personalities from numbers to perceiving different kinds of erotic stimulation with specific colours. We don't have a single, unifying theory of what happens in the brain to cause synesthesia yet, but many scientists believe it's the product of an increased communication between sensory areas that don't usually talk.

That kind of sensory overlap certainly seems similar to vEAR, but whether or not vEAR is a kind of synesthesia is very much still an open question. If it is, it could be pretty big for synesthesia research. The prevalence of vEAR seems to be much higher than that of other types of synesthesia.

And the scientists involved believe that the prevalence of sensory crossover seen in vEAR might challenge the idea that synesthesia is anything other than a part of normal variations between people. Maybe it's more normal to have senses cross over like this than we first thought. However, this isn't the only theory that could explain noisy gifs.

Some people have also highlighted the possibility that it's not actually a synesthesia-like process. It could be that visual brain areas are providing a sort of pre-emptive nudge to the ear to brace for expected sound. The acoustic reflex is a contraction of the stapedius muscle—a tiny muscle in the middle ear—that occurs in response to loud audio stimuli.

That decreases the vibrational energy transmitted to the cochlea, the part of the inner ear that translates vibrations into neural firing. The acoustic reflex is well documented in scientific literature, and can be used to gain insight into a lot of different hearing conditions. It also may produce an unexpected noise in the ear when it happens, since it pulls the inner ear into a slightly different shape.

So it might be that the acoustic reflex isn't just responding to the sound happening, but being prompted by the visuals predictive of a loud noise. That would explain why research has found that videos showing situations predictive of loud noises trigger vEAR. The brain might be pre-empting a sizeable sound and is letting the ear know, like, ‘hey, it's about to get real loud nearby!'.

While we haven't nailed down the exact mechanisms behind vEAR, or why some people have it while others don't, research is still ongoing to find out. What is clear, though, is that we've only scratched the surface when it comes to decoding the complex ways our senses interact. That, and sometimes tweeting about weird stuff results in actually advancing science.

Thanks for watching this episode of SciShow Psych, and thank you to Kimberly for asking. Our patrons on Patreon get to vote and decide what burning scientific questions we address. So if you want a chance at getting your question answered, check out patreon.com/scishow. [OUTRO ♪].