Does the physics of the skull protect mental privacy? · Grey Matter

For now, partly.

Does the physics of the skull protect mental privacy?

For now, partly. Scattering of light, attenuation of ultrasound in bone and the weakness of the brain's fields outside the head mean that no device can read detailed brain activity from a distance or without the person's knowledge, and even fMRI decoding of meaning needs hours of cooperative training inside a scanner. That protection is a fact of current engineering and can erode, because wearable sensors improve and decoders extract more from blurred signals every year. Ethicists and lawmakers therefore treat physics as a temporary safeguard and write protections for neural data before the technology removes it.