The scientists could hardly believe their eyes. 

For five years, the young man had lived in silent stillness. The doctors were convinced the accident had left him in a vegetative state. 

The man, Patient 23, was lying in a brain scanner. The researchers asked him questions. If the answer was yes, he should think of tennis. If the answer was no, he should think of walking around his house.

"Do you have any brothers?" The scanner lit up. He was thinking of tennis. It was the correct answer. Patient 23's brain was still functioning. 

Humans have been fascinated by the idea of being able to reach into someone else's mind and discover what they are thinking. 

After the dawn of lights and telephones, inventors promised mind-reading machines would be next. It was not to be. 

Now, scientists are on the brink of a breakthrough. 

Our understanding of thoughts has improved drastically. It was a topic that baffled Ancient Greek anatomistA biologist who studies the structure and bodies of living things, including humans.  Erasistratus, who could not comprehend where thoughts fit into the curious mass of the dissectedErisastratus cut up the brain so he could study it.  brain.

Using fMRIFunctional magnetic resonance imaging measures brain activity by detecting changes associated with blood flow. Blood flow is linked to the activity of neurons.  scanners and artificial intelligenceArtificial intelligence, or "AI," is the ability for a computer to think and learn. With AI, computers can perform tasks that are typically done by people, including processing language, problem-solving, and learning., researchers think they have cracked the code. Thoughts are a collection of interrelated points in a dense "meaning space". Different thoughts cause activity in neuronsNeurons, also known as nerve cells, are cells in the nervous system that use chemical or electrical signals to transmit information throughout the body.  in different areas of the brain.

New research is emerging all the time. In 2018, neuroscientists built a system that could guess the sentences that subjects were reading to themselves. A map of the concepts in our mind could be just years away. 

It is not just scientists who are working on mind-reading. In China, dozens of factories have started monitoring employees' brainwaves to read emotions. This April, brain implant company NeuralinkA neurotechnology company that develops interfaces to allow a brain to operate a machine directly. released a video of a monkey playing a game with its mind.

Lawmakers say the question is not whether we can build mind-reading machines, but whether we should. 

Mind-reading technology could transform lives.

But it also raises questions about privacy. "The mind - the only truly private place - has become inspectable from the outside," summarises one journalist. 

In Chile, politicians are working on a world first "neurorights" law. The bill would force scientists to register neurotechnologiesNeurotechnology involves machines that interact directly with human neurons. like medicines.

International bodies must act, says one neurobiologist.  "We want to do something a little bit more intelligent than wait until we have a problem and then try to fix it when it's too late."

For some, regulations would be enough to ensure mind-reading machines are not used to invade the privacy of citizens. Others think the danger is too great. Mind-reading should be banned. 

Yes. Allowing governments and companies to continue developing mind-reading technologies is too great a risk. Our thoughts are the one area we have complete privacy. Losing this privacy could put freedom in danger. 

No. The possibilities are endless. In the right hands, mind-reading machines could transform lives for the better. We should not disregard the potential of an entire field of scientific discovery over as-yet-unrealised fears. Regulation is the way forward.