Much like Robert Downey Jr. and grungy flannel shirts, animated GIFs are sensations of the 1990s that are enjoying an extended pop-cultural revival. Many pixels have already been spilled explaining the reasons behind this digital renaissance, but fewer have been devoted to the health dangers of this flashy trend.
Animated GIFs have crossed the barrier from blogs to news stories in record time. They can enhance a story, as in a piece from the Atlantic on how the U.S. gymnastics team earned its gold medal in London this past summer, by illustrating visual elements that cannot easily be conveyed through text. On the other hand, there are also stories in which a wall of GIFs verges on annoying.
But the GIF has all the attention-grabbing movement without the file size or time investment of video, so it’s likely only going to become more common in the eyeball-enticing digital economy. However, the rising popularity of the animated GIF does present a challenge for people with epilepsy who are sensitive to visual stimuli.
Of the 50 million people worldwide who suffer from some form of epilepsy, about 3 percent are photosensitive, meaning they can experience seizures in response to certain cyclic stimuli, like flashing lights or rapidly changing images. Triggers can include strobe lights, television shows -- like the infamous episode of the cartoon “Pokemon” that included a flashing red and blue scene that sent 685 Japanese viewers to the hospital -- and flashing elements on websites, including animated GIFs.
Malevolent hackers have exploited this feature before -- in 2008, a forum hosted by the Epilepsy Foundation was inundated with hundreds of messages containing embedded flashing GIFs. They also made posts with scripts that redirected a viewer’s Internet browser to another Web page designed to trigger seizures.
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RyAnne Fultz, who has pattern-sensitive epilepsy, recounted the attack in an interview with Wired.
"I don't fall over and convulse, but it hurts," Fultz said. "I was on the phone when it happened, and I couldn't move and couldn't speak."
On blogging platform Tumblr, many users tag posts that contain animated GIFs with labels like “epilepsy warning,” so sensitive viewers (or just those who prefer to read articles without 5-second loops of reality TV shows squashed in) can screen them out.
Not all GIFs necessarily trigger seizures, though. Animations with rapidly changing images or regular patterns are the ones to watch out for.
But “if it moves decently slow and doesn’t strobe, it’s safe,” one Tumblr user named Ali wrote.
According to the University of Wisconsin’s Trace research center, Web content will not provoke seizures if there are no more than three general flashes and no more than three red flashes within one second, or where the area of flashing is relatively small.
The Trace team has developed a tool called the Photosensitive Epilepsy Analysis Tool, or PEAT, which software and website developers can download to evaluate their applications to identify seizure risks.