What are 'sludge' videos on TikTok? Are they harmful?

(NEXSTAR) — Sludge is taking over TikTok but that doesn't mean what it sounds like. No, it's not a resurgence of the slime-making trend but instead a new way young people are watching videos on TikTok.

Think of it as picture-in-picture on your traditional TV — to the max.

Essentially, "sludge" is a TikTok video made up of several simultaneously playing videos. Typically, the video's audio will come from one root video while 1-5 other videos play in smaller windows on top of the main one.

For those of us already on information overload, this might sound like a nightmare, but the popularity of sludge content has grown over the past year. Sludge can be composed of completely unrelated things or have a general theme, like this "Family Guy" sludge video.

Companies have even used sludge to create ads, as in this video by prepaid wireless company Visible. There's even Pepsi sludge and Tums sludge.

The concept of a sludge video may seem pointless but TikTok creators may be producing them with the express purpose of keeping eyes on their videos. Since TikTok's algorithm takes video completion time into account when choosing whether or not to recommend videos to other users, making sure users watch a TikTok until the end is imperative for those looking to expand their reach, social media management platform HootSuite explains. Even though there's not one sure-fire formula for virality on TikTok, videos that are viewed in full — and viewed in full multiple times — are very likely to court favor with the platform's difficult-to-crack algorithm.

On paper, it makes sense for creators to use multiple screens to hook viewers on their videos. After all, with 1 in 6 teens telling Pew Research Institute they use TikTok and YouTube "almost constantly," there's lots of competition for the attention.

"We are so overstimulated by the constant flow of content available to us that the ability to watch multiple things at one time is for many, a necessary factor in order to stay engaged," marketing company Weber Shandwick said in a TikTok video about sludge last year.

But just what exactly is sludge doing to viewers' brains? Likely nothing beneficial.

Because while sludge content works in the same way as if you were watching television while scrolling through social media and answering text messages (called "media multitasking"), research shows that this kind of behavior impairs focus significantly, making it harder for young adult brains to form memories of certain moments.

And while most of us believe we are good multitaskers, experts say very few people actually are. What's actually happening when most people think they're managing several tasks at once is what writer Thatcher Wine calls "task switching."

"All that task switching comes at a cost," Wine, author of "The Twelve Monotasks: Do One Thing at a Time to Do Everything Better," previously told TODAY. "It overloads our brains and causes a significant amount of stress... studies have shown that tasks take longer and we make more mistakes than if we had done one thing at a time."

Many medical experts agree that multitasking is likely rarely happening — so viewers of sludge content are probably not successfully watching and taking in one video, but failing to watch several videos at once.

Finally, there's also one other, even more insidious effect that sludge content can have on young brains.

As explained by CBC News reporter Eli Glasner, sludge content also becomes tricky when some of the content included in the video is more extreme. Glasner points to self-described misogynist Andrew Tate, who encouraged his fans to include his videos in sludge content. Ideas by Tate — who is currently awaiting trial on charges of rape and human trafficking — can easily be snuck in alongside more innocent videos. So even if the audio for one specific video isn't playing in the sludge video, young people can often still see captions, or else, become interested in finding out more based on the tile.

With all this in mind, it's important for parents to continue vigilance around what their children are coming across on TikTok and other video platforms. For adults who use TikTok, it's important to be mindful of how your engaging and with what — strategies for mindful social media use include setting your own limitations and understanding how what we're watching is making us feel.