The bizarre reason why you can hear this GIF, even though it’s silent

There’s a GIF currently doing the rounds of a pylon skipping over the wires of two other pylons. This is actually the least strange thing about the animation, it turns out. As Lisa DeBruine, from the Institute of Neuroscience and Psychology at the University of Glasgow, asks – why are we able to “hear” this silent GIF?

The bizarre reason why you can hear this GIF, even though it's silent

As the pylon lands, the animation – made by HappyToast – appears to shake. This is the moment that, at least for many people, a thudding sound is heard. The GIF itself has no audio, so why do we think there is a noise?

On Twitter, a few people have pointed to a possible physical reason for the illusion. It could be the case that GIF creates an acoustic reflex, they claim, with part of the inner ear contracting in response to the sight of the camera shaking, which the brain interprets as an incoming sound wave.

We reached out to Trevor Cox, professor of acoustic engineering and author of books including Sonic Wonderland: A Scientific Odyssey of Sound. Instead of a physical effect, he points to another reason for the illusionary thud:

“There are well known cases (synaesthesia) of sensory inputs crossing to other domains, e.g. people who associate colours with sounds,” he said. “So it doesn’t surprise me that for some viewers a sound results.

“We also tend to think of our senses as being separate, but our brain collates responses from all senses to work out what is going on. So I would say it is likely to be some effect in the brain rather than a physical effect like the acoustic reflex.”

Sounds possible. To dig a little deeper into synaesthesia, we contacted Professor Julia Simner, a research group leader in the MULTISENSE lab at University of Sussex. MULTISENSE has a large grant from the ERC (European research council) to study synaesthsia across a person’s lifetime.

“Those who hear it are experiencing vision-sound synaesthesia,” she said. “Synaesthesia is a trait that affects a small percentage of the population and gives rise to unusual additional perceptual experiences. In vision-sound synaesthesia, the visual movements (often something pulsing, or moving rhythmically) can trigger sound associations.

“I don’t have synaesthesia so don’t hear anything – but I notice that this looks to be a particularly good trigger – it has all the elements needed: something repeating… and something that would in fact make a loud noise in real life, so I’m not surprised that many people have been hearing it.”

Chris Fassnidge, a PhD student exploring synaesthesia at City University of London, suggests the effect may be the result of a synaesthetic pairing between movement and sound: 

“Movement to sound synaesthesia has been studied very rarely,” he said. “A 2008 paper by Melissa Saenz and Christoff Koch called it hearing-motion synaesthesia. I suspect the noisy gif phenomenon is closely related, although perhaps a subtler form of the condition. It may be a proto-synaesthesia, and in our lab (led by Elliot Freeman at City University of London) we refer to it as the Visually-Evoked Auditory Response (vEAR for short), or the visual ear.” 

Fassnidge went on to offer an explanation for why, if the phenomenon is related to synaesthesia, so many people seem to be experiencing it with HappyToast’s GIF:  

“A recent study of ours suggested that as many as 1 in 5 people may experience some form of vEAR, which is considerably higher than most estimates of other forms of synaesthesia, which tend to be around 2-4%. Interestingly, the very reason why the phenomenon is so common, the high real-world frequency of audiovisual co-occurrence, may explain why so few of us notice vEAR until our attention is drawn to it.

“Because these pairings happen so often, we may have learnt to ignore them, or tuned them out. Alternatively, the imaginary sound may often be masked by the real sound of the moving object. How would you know if you could mentally hear my hands clapping if the sound they make drowned out the vEAR? We may even think the sound is real when it isn’t – I might assume I am hearing the footsteps of a person walking on the other side of the street, when really the sound exists only in my mind.

“So this may be a common phenomenon because we grew up surrounded by noisy movements, but for that exact reason we may not even know we have this unusual ability until the noisy gif suddenly came along in the last few years!”

Whether or not the GIF triggers an acoustic reflex or there’s some degree of synesthesia happening, more extensive tests will be needed to pin down exactly what elements of the silent clip make it so… noisy. DeBruine suggests that it would be a “cool student project” to test variations, from whether the camera shake is essential to whether the effect interferes with perceptions of real sounds. 

“The main way to evaluate everyone’s various explanations is to check if they also explain why this particular GIF causes such a strong and surprising effect, while most other GIFs produce no illusory sound (or something more voluntary, akin to reading in your head),” DeBruine told Alphr. 

If you’re like to contribute to a study about whether different types of visual motion evoke an imaginary sound, Fassnidge and his fellow researchers at City University of London are conducting an online survey about the phenomenon

Image: HappyToast

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