Scientists have discovered why we flinch when someone gets hurt on screen

Now scientists have explained what's behind this effect: the brain doesn't just "watch" a scene, but partially plays it back on its own body.

Researchers from the University of Reading (UK), the Free University of Amsterdam and the University of Minnesota have shown that areas of the brain that were thought to be purely visual are actually organised according to the principle of a "body map" and can elicit a response similar to touch.

The work is published in the journal Nature.

The brain "projects" other people's pain onto our bodies

The team analysed the brain activity of 174 people who watched snippets of films like The Social Network and Inception. Using new techniques for processing fMRI data, the scientists found:

• visual areas of the brain were activated as if the viewer's own body was being affected;
• these areas revealed maps of body parts similar to those usually found in areas responsible for touch;
• when participants saw someone being tickled or hurt, the patterns of activity corresponded to the same body part in the observer - face, arms, legs, etc.

In other words, the brain automatically "superimposes" what it sees on its own bodily coordinates and simulates the sensation of touch, even though no one is physically touching us.

Scientists note that this connection works in the opposite direction: when we, for example, walking through a dark room almost blindly, the signals from touch help the visual system to build an internal map of space.

Two systems of "body maps" in the visual cortex

Researchers have identified two principles of such a map:

• In the dorsal (upper) parts of the visual system, areas responsible for different parts of the body correlate with their position in the visual field: "leg area" - with the lower part of the picture, "face area" - with the upper part.
• In ventral (lower) sections, the map is no longer linked to the position in the frame, but to the object itself: what matters is whether it is the body part, not where it is on the screen.

This shows that the visual system is tightly integrated with touch and is constantly "translating" what is seen into body language.

The authors believe the discovery could help to better understand and diagnose a number of conditions, such as:

• autism spectrum disorders, where the ability to "internally simulate" other people's experiences may be impaired;
• other sensory integration disorders.

Importantly, these mechanisms can be investigated simply while watching the film, without tedious special tests, which is particularly relevant for children and patients with disabilities.