New Delhi, Nov. 10 -- People buying a brain-sensing wearable to track sleep or concentration may be contributing to something larger than their own daily report. A Science investigation found that consumer neurotechnology companies developing AI brain models initially failed to describe that purpose in their privacy policies, even while discussing the projects elsewhere.

The November 4 investigation reviewed 57 consumer EEG companies worldwide. Science reported that four had no privacy policy and 11 had policies covering website visitors rather than the brain-data service. Those figures describe disclosure problems across the sample, not a finding that all 57 companies trained AI models on customer recordings.

Current documents tell a m...