Who owns a measured thought?

Brain-computer interfaces are no longer just medical devices. Focus headbands, earbuds that pick up electrical activity, headsets that record where your gaze lands. Tools sold as wellness or productivity aids, collecting data produced directly by the nervous system.

The legal question is easy to ask and hard to answer: who owns that data, and what can be done with it?

The first answers

Some legal systems have started to answer. In 2021 Chile amended its Constitution to protect brain activity and the information derived from it. In the US, Colorado added neural data to the sensitive data covered by its privacy law in 2024, and California followed a few months later.

In Europe the GDPR does not mention neural data. It may fall under health or biometric data, but not always: a signal measuring attention at work is not necessarily health data. The risk is a grey zone exactly where clarity is most needed.

The point that interests me

I have been writing about BCIs and law for years, and one thing seems clear to me: the problem is not only privacy. Neural data does not just say who you are. It can hint at what you are about to do, before you decide. It can be used to adapt what you see while you are looking at it.

At that point, protecting the data is not enough. We need to protect the process by which you form a judgment. It is the same line I draw with Habeas Mentem: the understanding of a text can be measured, but the mind cannot be read.