Can anyone read your mind?

A decoder can now recover the gist of what someone is hearing or imagining. It needs their cooperation, and that turns out to be the interesting part.

ShallowsKnownInspect the question

The question

Mind reading was a thought experiment for most of the history of the question. It is now a laboratory result with published limits, which is a better position from which to worry about it.

The limits are not incidental. They come from how the decoder and the measurement work, and they are what makes the finding describable.

What has been done

Known. Strongly supported by evidence and broadly established.

Strongly supported by evidence and broadly established.

What the decoder does

A 2023 study recorded the brains of three participants for sixteen hours each while they listened to stories, and trained a model on the recordings. Afterwards it could generate text that recovered the meaning of what a participant was hearing, imagining, or watching in a silent film.

The output is a paraphrase. It captures the gist and often gets exact words wrong, because it scores candidate sentences by their meaning, and different wordings of one meaning look alike to it.

What it is not

A scanner can now read anyone’s thoughts.: The decoder is trained on many hours of one person’s own data. Built from other people’s recordings alone, it did barely better than chance, and later transfers between people still needed the new person in the scanner.
It produces a transcript of inner speech.: It produces a paraphrase of meaning. Exact wording is often wrong.
It works whether or not you consent.: Training requires cooperation, and a trained decoder could be resisted by a subject silently naming animals or telling themselves a different story.

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The cooperation requirement is a result, not a caveat

The same study tested that directly, and reports that cooperation is required both to train the decoder and to apply it. Its authors add that later developments might get around both; in a 2025 follow-up they judged that the requirement still holds.

So the finding is two findings. Meaning can be recovered from a non-invasive recording, and mental privacy currently has a physical basis rather than only a legal one.

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Privacy held here because each decoder had to learn one brain and could be refused attention, not because anyone designed it that way.

What it does not reach

Uncertain. Meaningful scientific, historical or philosophical disagreement remains.

Meaningful scientific, historical or philosophical disagreement remains.

How far the technique goes

The technique is a development rather than a break. A 2006 review already described decoding simple mental states from imaging data, which way a pattern was moving or which of two overlapping patterns a person was attending to. What changed by 2023 is that the target became continuous meaning rather than a choice between categories.

Two things could take it further. Hardware is one: blurred to the resolution of current portable systems, the 2023 recordings still decoded around half of the moments in a story.

Sharing models between people is another. In 2025 the same group carried decoders to a new person using seventy minutes of that person’s recordings, of stories or of silent films, and reached around half the performance of a decoder trained on the person’s own ten hours. The authors hold that cooperation is still required, because the alignment needs the new person’s recordings.

The slowness of the blood-flow signal is a limit of another kind. It rises and falls over about ten seconds, so each image mixes the response to more than twenty words, and a language model has to propose the words the image cannot pin down. The authors found their own models a major source of error, so better modelling should help. No modelling recovers information the measurement did not carry.

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Whether thought is the right target

Decoding works on what a person is perceiving or deliberately imagining, which is the part of mental life that behaves like a signal. Much of mental life is not that.

Experiments on introspection find something different: asked what led to a choice or a solution, people name causes the experimenters know had no effect, and deny ones the experimenters know were at work. There may be less to read than the phrase suggests.

Telling more than we can know: Verbal reports on mental processesNisbett and Wilson, Psychological Review · 1977

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The evidence

Primary research, scientific institutions and archives. Links open at the publisher.

The currents

Where this question leads

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Let the ocean choose