If you have ever opened Instagram for “just five minutes” and suddenly realised you have been scrolling for much longer, a new brain study may offer part of the explanation.

Researchers found that short videos people enjoyed watching to the end were associated with reduced activity in two brain regions involved in cognitive control. The study, published in NeuroImage, used brain imaging to examine what happens as people freely watch short-form videos.

The finding offers a possible explanation for why highly engaging clips can hold attention so effectively. But it does not mean Reels, TikTok or YouTube Shorts “switch off” the brain, and it does not show that short videos cause permanent brain damage.

Instead, the research points to a more specific effect: when people become absorbed in content they find rewarding, brain systems involved in monitoring and controlling behaviour may become less active.

What did the new short-video brain study find?

The study involved 56 young adults who watched short videos while researchers monitored their brain activity using functional magnetic resonance imaging, or fMRI.

Researchers also used magnetic resonance spectroscopy to examine concentrations of certain brain chemicals, including glutamate and GABA, which are involved in communication between nerve cells.

The researchers focused on two areas:

• Dorsal anterior cingulate cortex (dACC): involved in monitoring behaviour, attention and decision-making.
• Dorsolateral prefrontal cortex (dlPFC): important for cognitive control, working memory and regulating behaviour.

Both regions are associated with the brain’s ability to manage attention and decide whether to continue or change an activity.

When participants watched videos they preferred and stayed with until the end, activity in both regions fell significantly compared with videos they disliked or stopped watching early.

The researchers described this reduction as deactivation of the cognitive control network.

That distinction matters. Reduced activity in these regions does not mean the brain became inactive. It means that particular systems involved in cognitive control showed lower activity while participants were absorbed in preferred content.

Why would cognitive control decrease while watching a favorite video?

One possible explanation is that engaging content requires less conscious effort to maintain attention.

Think about the difference between forcing yourself to read a dense report and watching a video that immediately captures your interest.

With the report, you may repeatedly monitor yourself:

Am I paying attention? Should I keep reading? I need to finish this.

With an entertaining video, that monitoring may become less necessary because the content itself is holding your attention.

The researchers found something particularly interesting alongside the reduced activity: communication between the dACC and dlPFC became stronger during short-video viewing, especially when participants watched videos they preferred.

In other words, lower activity did not necessarily mean the two regions stopped working together.

Instead, the pattern suggests that the cognitive control system may have shifted into a different state while participants were immersed in preferred content.

Does this explain why endless scrolling is so difficult to stop?

It may help explain it, but the study does not prove that it does.

Short-form video platforms are designed around a continuous stream of content. Each clip ends quickly, and another one is immediately available.

If a video is entertaining, there is little natural stopping point. Before someone has to make a conscious decision to leave, the next clip has already started.

The new findings suggest that highly preferred content may be accompanied by reduced activity in brain systems involved in cognitive control while attention is strongly engaged.

That could contribute to the feeling of being “locked in” to the content.

But there is an important limitation: participants were studied while watching videos in a controlled research setting. The study does not establish that the observed brain state persists after someone puts down their phone.

It also does not prove that repeated exposure to short videos permanently changes the brain.

What role do glutamate and GABA play?

The researchers also looked at neurochemicals in the dACC, including glutamate and GABA.

Glutamate is the brain’s major excitatory neurotransmitter, while GABA is its primary inhibitory neurotransmitter. Their balance is important for regulating neural activity.

The study found that participants with higher resting glutamate levels in the dACC showed less suppression of activity in the cognitive-control regions while watching preferred short videos.

That does not mean glutamate levels determine whether someone will become addicted to Instagram or TikTok.

It is an association observed within this particular study, and more research is needed to understand what it means.

The finding is nevertheless useful because it suggests that differences in brain chemistry may influence how people respond to highly engaging short-form content.

What does this have to do with attention?

Short-form video is different from many traditional forms of media because the viewer can encounter a new topic, visual style or emotional stimulus every few seconds.

A comedy clip can be followed by a news video, then a cooking tutorial, then a sports highlight and then a completely unrelated meme.

That rapid change may place different demands on attention and memory than watching one continuous piece of content.

Researchers are increasingly interested in whether the way people consume short videos matters as much as the amount of time they spend watching them.

This distinction is important.

Watching a 30-minute documentary without interruption is not the same cognitive experience as watching hundreds of short clips in which the subject, context and goal change repeatedly.

Have other studies found effects on memory?

Yes, although the evidence is still developing.

A 2025 study by Nicholas Barton and Michael Smyth examined what happened when participants experienced unlimited context-switching between short videos. Participants subsequently performed worse on a task involving prospective memory.

Prospective memory is the ability to remember that you need to do something later — for example, remembering to send an email after a meeting.

A separate study published in Behavioral Sciences in June 2026 involved 106 students in one experiment and 64 in another. Researchers reported that prolonged short-video viewing was associated with reduced prospective-memory accuracy, although the effect varied depending on the attentional demands of the task.

These studies raise an important possibility: the cognitive effects of short-form video may depend not simply on watching videos, but on how the viewing experience is structured.

Rapid context switching, continuous scrolling and prolonged engagement may place different demands on attention and memory.

Does this mean TikTok, Instagram Reels and YouTube Shorts are damaging your brain?

No. That conclusion would go beyond the evidence.

The studies described here generally involve relatively small or specific participant groups, controlled experiments and measurements of particular cognitive or neural outcomes.

They do not establish that short-form video causes permanent structural brain damage.

There is also an important difference between observing a temporary change in brain activity and demonstrating long-term neurological harm.

The brain constantly changes its activity depending on what a person is doing. Concentration, exercise, conversation, sleep and watching a movie can all produce different patterns of neural activity.

So the observation that certain brain regions become less active during an engaging activity is not, by itself, evidence of damage.

The bigger question is how we use short-form video

The more interesting question may not be whether short videos are “bad for the brain.”

It is what happens when highly engaging content becomes the default way we consume information and entertainment.

Several factors may matter:

• Duration: How long someone spends watching continuously.
• Context switching: How frequently the subject of attention changes.
• Control: Whether the viewer intentionally chooses each video or simply accepts whatever appears next.
• Stopping points: Whether there is a natural reason to stop watching.
• Content: Educational, entertaining and emotionally stimulating videos may place different demands on attention.
• Timing: Watching short videos immediately before sleep or during work may have different consequences than watching them during dedicated leisure time.

This is why the emerging research should not be reduced to “TikTok damages your brain.”

The science is more nuanced — and arguably more useful.

Why “just one more video” can become a surprisingly hard decision

The latest findings provide another piece of the puzzle surrounding compulsive-feeling scrolling.

When people encounter content they find highly rewarding, their attention can become deeply focused. At the same time, activity in brain regions associated with monitoring and cognitive control may decrease.

Combine that with an endless stream in which every video is immediately replaced by another, and the viewer may have few natural moments to ask whether they actually want to continue.

That does not mean the brain has been “hacked.”

It means the environment is exceptionally good at keeping attention occupied.

And that may be the most useful takeaway from the research: the difficulty of putting down your phone may have less to do with a damaged brain and more to do with how effectively short-form platforms capture and maintain attention.

What the research does — and does not — show

What the latest study found

• 56 young adults participated.
• Researchers used fMRI to measure brain activity during short-video viewing.
• Researchers also used magnetic resonance spectroscopy to examine brain chemicals.
• Preferred videos were associated with reduced activity in the dACC and dlPFC.
• Communication between the two regions became stronger during preferred-video viewing.
• Higher resting glutamate levels in the dACC were associated with less suppression of activity.

What it did not prove

• That Reels, TikTok or Shorts cause permanent brain damage.
• That short-form video causes addiction.
• That the observed brain activity changes continue after viewing ends.
• That every type of short video produces the same effect.
• That reducing short-video use will necessarily reverse the observed brain patterns.

The bottom line

The new study does not reveal that Instagram or TikTok is secretly “turning off” your brain.

It reveals something subtler: when people become absorbed in short videos they enjoy, brain regions involved in cognitive control show reduced activity, while communication between those regions becomes stronger.

Combined with other research linking rapid context-switching and prolonged short-video consumption with certain memory and attention effects, the findings add to a growing scientific debate about how the format shapes cognition.

But the evidence is not a verdict against short-form video.

For now, the strongest conclusion is much narrower: highly engaging short videos can put the brain into a state where attention is strongly captured and conscious control may play a smaller role.

That may be enough to explain why “I’ll watch one more” so often turns into twenty.