Short-form video platforms exploit brain's reward system, study finds

For many of us, the day often starts with a swipe. Before getting out of bed, we might scroll through TikTok, Instagram Reels or YouTube Shorts. A few clips become a few dozen. Minutes become an hour. Then, later in the day, we return for more.

Researchers at Germany's University of Bayreuth examined the phenomenon, especially in children and adolescents.

The review, published in the journal European Child and Adolescent Psychiatry, analyzed 42 studies involving nearly 30,000 participants, most of them adolescents and young adults.

Importantly, the authors examined something often overlooked in public debate: The mechanics of the platforms themselves.

Far from TV on a smaller screen

The researchers identified three features common to short-form video platforms: The personalization of algorithms, the unpredictability of the infinite scroll and the novelty of rapidly switching among videos.

These features create a media environment unlike television, traditional online video or older social networks, they say.

Short-form video platforms work differently. Algorithms continuously select content, users rarely need to make decisions and there is effectively no natural stopping point.

"TikTok is fundamentally different from television," Aza Raskin, co-founder of the Center for Humane Technology, told DW. "On the other side of a TikTok screen is a massive supercomputer pointed directly at your brain. It is trained on the behavior of 3 billion other human primates."

"The attention economy is essentially a race to the bottom of the brainstem," Raskin said. "If TikTok doesn't occupy your time, Facebook, Instagram or another platform will."

"This triggers a ruthless knife fight for human attention," he added.

The hit and miss of dopamine

Scientists have long understood that highly rewarding experiences activate the brain's reward system. Short-form videos (SFVs) are especially effective at exploiting that system.

Anna Lembke, associate professor of psychiatry at Stanford University School of Medicine and author of the book Dopamine Nation, told DW that SFVs combined several features that make them unusually compelling.

"Moving images are themselves like catnip for the mammalian brain," she said. "Short-form videos are a more potent form, and hence more addictive, leading to video chaining, akin to chain-smoking,' wherein once we begin it's hard to stop, even when we want to."

Over-stimulating the brain's reward system with highly rewarding unnatural triggers like gambling and binge-eating causes a flood of dopamine, the brain's reward and pleasure neurotransmitter. To protect itself, the brain "downregulates," with cells decreasing the number of dopamine receptors needed to experience pleasure. Repeated hyperstimulation can, over time, make the brain less sensitive to reward.

"We need more videos over time, not to get high, but just to feel normal," she said. "And we lose our ability to engage in and take joy in other, more modest rewards, like watching a sunset, sharing a meal with friends, or reading a good book."

According to Lembke, the endless nature of modern feeds may gradually change how that reward system responds: "Endless scrolling leads to reward desensitization, that is, less dopamine being released over time in response to similar rewards, such that more videos with more extreme content are needed to get the same effect."

The result can be a paradox familiar to many users: Continuing to search for the next rewarding clip even when the experience itself is no longer particularly enjoyable.

Why personalization may matter most

While infinite scrolling receives much of the public attention, Ben Rein, a neuroscientist, science communicator and author of the book Why Brains Need Friends, believes that the real power lies in appealing to the individual.

"Infinite scroll and novelty matter, but they're delivery mechanisms; personalization is the engine," Rein told DW.

He describes a typical TikTok feed as "a system running thousands of tiny experiments on you, learning faster than you do what keeps you watching."

Rein also argues that personalization becomes especially powerful when combined with the unpredictability Lembke describes: "It's the combination, with personalization as the part that makes it so attractive and scalable across every human that uses social media."

Lembke sees a similar dynamic. "The algorithms evolve the perfect drug of choice for each unique person in real time, through our interactions with the platform, which also makes the exchange feel organic and alive," she said.

"Novelty overcomes the boredom that develops with tolerance: That is, needing more potent versions over time to get the same effect," she added. "Unpredictability engages the treasure-seeking, foraging part of our brain that evolved to keep us persistent and striving in a harsh ecosystem of rare and uncertain rewards, making those rare rewards that much more rewarding when we find them."

What comes next?

Across the 42 studies examined by the University of Bayreuth team, several themes emerged repeatedly.

They include higher attentional difficulties, lower working-memory performance, higher anxiety and depression, weaker self-regulation, and addiction-like patterns. However, the research team emphasized that the evidence remains limited.

"There is still insufficient evidence to conclusively claim that short-form video platforms cause 'brainrot' or extreme dopamine effects," lead author Marlene Ebster told DW.

Rather than recommending blanket bans, the authors suggest helping young people understand how recommendation systems work and how platform designs influence behavior.

For Rein, the next frontier for platform designers is probably deeper personalization.

"As recommendation models improve, and increasingly as AI can generate or tailor content to the individual in real time, the gap between 'what you'd enjoy' and 'what you're shown' will likely keep shrinking."

The growing sophistication of artificial intelligence may also become increasingly important.

"We are nowhere near the peak of attention engineering," said Raskin. "We are now entering the era of AI 2.0, which is generative AI. This technology can actually create entirely new content from scratch."

"The capabilities of generative AI to maximize attention, ranging from synthetic media to highly personalized synthetic relationships, will completely dwarf the power of any psychological engineering we have seen to date," he warned.

Edited by Ben Knight