Watching Reels may switch down parts of the brain linked to focus, study finds

If you have ever opened Instagram for “just five minutes” and found yourself scrolling much longer, a new brain study offers a possible explanation. Researchers found that short videos people enjoyed were linked to reduced activity in two brain regions involved in cognitive control.

The study, published in NeuroImage, involved 56 young adults. Researchers used functional MRI (fMRI) to watch brain activity while participants freely viewed short videos. They also used magnetic resonance spectroscopy to examine chemicals including glutamate and GABA. The finding does not mean Reels or Shorts switch off the brain, nor does it prove that short videos cause permanent brain damage.

What happens to the brain while watching?

The researchers focused on the dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex (dlPFC).

These areas are part of the brain's cognitive control network. They are involved in functions such as monitoring behaviour, managing attention and deciding when to change what we are doing.

When participants watched videos they liked and watched until the end, activity in both regions fell significantly compared with less-preferred videos that participants stopped early. The researchers described this as deactivation of the cognitive control network. Interestingly, communication between the dACC and dlPFC became stronger while people watched videos, particularly preferred ones. The study also found that people with higher resting levels of glutamate in the dACC showed less suppression of activity in these regions.

Does this explain endless scrolling?

Possibly, but researchers are not saying the study proves that. The idea is that highly engaging videos may reduce activity in brain systems involved in monitoring and controlling behaviour while attention becomes focused on the content.

That could help explain why stopping can feel difficult once someone becomes absorbed in a stream of entertaining clips. But the study was conducted in a controlled setting and does not establish that the effect continues after people stop watching.

Other studies have raised similar questions

The findings add to growing research into how rapid short-video consumption affects cognition. A 2025 study by Nicholas Barton and Michael Smyth found that participants exposed to unlimited context-switching between short videos performed worse on a prospective-memory task afterwards. Prospective memory is the ability to remember something you intend to do later. A separate study published in Behavioral Sciences in June 2026 involved 106 students in one experiment and 64 in another. It found that prolonged short-video viewing reduced prospective-memory accuracy, although the effect depended on the attentional demands of the task.

Together, the research suggests that how we consume short-form video may matter, particularly when viewing involves rapid switching and prolonged engagement.

But there is an important distinction: none of these studies shows that watching Reels, Shorts or TikTok causes permanent brain damage.

The latest research instead provides another clue about why highly engaging short videos can capture attention so effectively and why “just one more” can be surprisingly difficult to resist.