A silent gif of pylons playing jump rope with their wires surprised many last week when they heard the thumping of the structure striking the ground eventhough the clip had no sound. The playful meme has sparked conversations among researchers and swarms of articles about how we perceive the world. And while many have suggested the strange effect to be the result of a type of synesthesia—a condition in which one sense evokes another—there may be other, more simple explanations.
The discussion of this “noisy” gif began when Lisa Debruine, researcher at the University of Glasgow, posted the joyful pylons asking if anyone could explain why she was hearing the thump of their jumps. And she wasn't the only one listening in on the silent gif. Based on her informal Twitter poll, three-quarter of the over 280,000 people providing data about their experiences heard a thudding sound while watching the silent animation. (This number does not include the roughly 35,000 who opted not to share their experiences, responding only to see the results of the poll.)
The animation of the pylon jumping rope has certainly caught people's attention. It was was originally created by @HappyToast in response to a Bt3a weekly image challenge he later reworked for BBC’s The Wrong Door comedy show, reports Belfast Telegraph. But the effect isn’t unique: people quickly found other variations on the theme including this scene from My Neighbor Totoro, while the subreddit /r/noisygifs houses an ongoing collection of gifs' whose doesn't stop viewers hearing them.
How can these silent gifs make so much noise?
The go-to explanation for many has been some form of synesthesia. "I suspect the noisy gif phenomenon is closely related to what we call the Visually-Evoked Auditory Response, or vEAR for short," Chris Fassnidge, researcher at London's City University, told Rozina Sini reporting for the BBC. People with this subtle form of synesthesia fill in an expected sounds from visual cues. While synesthesia is rare (only two to four percent of the population experiences it), as Angela Chen at The Verge reports, vEAR may impact up to 20 percent of people.
But it may be simpler than that.
“We cannot stop other sensual inputs and referring further cognitive processing,” Claus-Christian Carbon, a researcher at the University of Bamberg, wrote in an email to Smithsonian.com. Humans are constantly processing multisensory input. “Typically, the integration of many channels enables that we use the redundancy and richness of information to perceive one single event—one solution of the variety of possible ones,” he writes.
With the jumping pylon, “We lack the acoustic quality of the scene,” Carbon writes, “But we are used to [hearing] typical noise while swinging a jump rope, and so this sound is directly associated with such an event—just because it is very common, very probable.” Instead of being synesthesia, he says it’s likely that viewers can hear the gif because of a multisensory or cross-sensory illusion, a subclass of perceptual illusions.
In response to speculation following Debruine’s Twitter post, @HappyToast indulged the “What if…” scenarios, narrowing down theories by cropping out the pylons and leaving just the shaking ground as a visual cue implying sound.
The thump is almost entirely in the shake, if you crop out the pylons themselves you can still hear it. They just give it height. pic.twitter.com/3LZK1g24yZ— HappyToast (@IamHappyToast) December 4, 2017
For many who had already seen the full image, the shaking ground was enough to still evoke that thudding noise. Similarly, after @HappyToast found the version created for The Wrong Door that lacks the important ground shake, few filled in the blanks with an implied thud.
Visual effects supervisor Mark Savela agreed with Carbon, identifying that the effect is a form of optical illusion or sensory memory. He tells Smithsonian.com the technique is commonly used in the film industry. “For us it’s just a simple camera shake used to emphasize an impact, something heavy landing or a space ship or car passing very close to camera.”
Carbon says an example of how these perceptual illusions can lead us astray is the McGurk effect, an illusion exploring how we integrate both auditory and visual cues in interpreting sound by mismatching components to create the perception of a third sound.
“Generally, such illusions do NOT show how malfunctioning our perception works,” writes Carbon, pointing to a research paper where he identifies this as a way in which we demonstrate, “our incredible, highly complex and efficient capabilities of transforming sensory inputs into understanding and interpreting the current situation in a very fast way.”
Still one more theory could help explain the noise: The effect may well be in how we’re talking about it. Debruine’s original query and poll assumed the that people would hear something, even describing what that sound could be, both things known to cause problems when collecting eyewitness testimony. The prevalence of article headlines about the noisy .gif telling people what to expect could also be enough to trigger auditory hallucinations, and as researcher Tanya Lurhman at Stanford University has shown, this effect may be stronger in some cultures than others.
All in all, it seems that there's no one right answer. The reason is likely the result of many factors that all influence our perception of the "thump" from the silently playful pylons.