Two Kinds of Mental Privacy: What Speech Decoding Does and Does Not Threaten

In the article "Speech Restoration and Mental Surveillance as Conflicting Ethical Concerns in Neural Speech-Decoding Research," Narayan Sankaran and Winston Chiong distinguish speech-decoding strategies by whether they read brain signals tied to communicative intent, softening the common equation of neural decoding with mind reading. This commentary situates their distinction within a broader conceptual map of mental privacy, borrowing Noam Chomsky's distinction between the narrow and broad senses of the language faculty. Mental privacy in the narrow sense concerns the decoding of occurrent mental states-thoughts, feelings, intentions-the domain Sankaran and Chiong address. Mental privacy in the broad sense concerns statistical inferences about traits, risks, and dispositions from brain data, which can wrong a person without there being any decoding of their mental state at all. The two senses implicate different harms, different relations to cognitive liberty, and different regulatory logics: intent-based authorization for narrow-sense decoding, purpose limitation and proportionality review for broad-sense inference. Distinguishing them clarifies what current speech-decoding research does, and does not, threaten.