How Brain Waves Shape Your Sense of Self

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HHow do humans know where the self ends and the world begins?

It is a feeling essential to daily experience and vital for survival, but it can easily be disrupted. Take the classic rubber hand illusion. A person’s real hand is hidden while a rubber hand is placed in plain sight. When both hands are tapped at the same time, the person may begin to feel that the rubber hand is theirs. But even slight variations in timing can make that strange feeling go away.

So how does the brain detect different sensory signals coming from the body? It relies on certain rhythmic waves called alpha waves, which pass through the parietal cortex, responsible for processing touch, body position and other bodily sensations.

Now, a team of scientists from Karolinska Institutet in Sweden has discovered that individual differences in the frequencies of these alpha waves can determine the extent to which a person perceives their body as distinct from the outside world. If alpha waves run faster, your brain is better able to decide what is really part of you. If they run slower, the distinction between self and others becomes a little blurrier. The scientists recorded EEG signals from 106 participants while testing them on the rubber hand illusion, reporting their results in Natural communications.

Read more: »Does anyone really know what time it is?»

“We have identified a fundamental brain process that shapes our continued experience of being embodied,” explained lead author Mariano D’Angelo, a researcher at the Department of Neuroscience at Karolinska Institutet, in a statement. “The findings could provide new insights into psychiatric disorders such as schizophrenia, in which the sense of self is disrupted.”

People with schizophrenia tend to have slower alpha waves. The findings could also help scientists create better prosthetics and virtual reality experiences: the more precise the timing of sensory feedback, the more real these augmentations will seem.

To carry out their experiment, the scientists manipulated the frequencies of the taps delivered to the rubber hand and the participant’s real hand, with delays or accelerations of up to 500 milliseconds. Then, they asked the participants to judge whether the fake hand looked like theirs. They also tested participants on their ability to judge timing differences between brief tactile and visual prompts, which were previously linked to differences in the frequencies of their alpha waves.

What they found was that there was a strong overlap between the two: people’s ability to discern differences in the timing of external cues and their tolerance for temporal shifts when deciding whether the rubber hand looked like their own.

In a second part of the experiment, the scientists were able to show that it was not just a matter of correlation, but that there was a causal link. Using gentle brain stimulation, they temporarily speeded up and slowed down alpha waves in the parietal cortices of 30 participants. They found that these manipulations influenced how likely they were to feel that the rubber hand was theirs, as well as their ability to judge differences in timing between external light and tactile cues.

Finally, they used mathematical modeling based on Bayesian reasoning to show that changes in alpha frequency did not change participants’ beliefs so much as their uncertainty about the source of sensory signals. Faster alpha waves appeared to lead to cleaner, more reliable timing signals, while slower waves led to noisier, fuzzier timing signals.

“Our results help explain how the brain solves the challenge of integrating signals from the body to create a coherent perception of the self,” said Henrik Ehrsson, a neuroscientist at Karolinska Institutet and co-author of the study.

They say timing is everything. Apparently this truism can extend to our self-esteem. We are, at least in part, the pace we maintain.

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Main image: Stranger Man / Shutterstock

• Kristen French

  Published on January 12, 2026

  Kristen French is an associate editor at Nautilus. She has worked in science journalism since 2013, reporting and writing articles and news for publications such as Wired, Backchannel, The Verge, And New York Review. She holds a master’s degree in science journalism from Columbia University.