Information rate of a brain-to-brain channel

The information rate of a BBI is how many bits per unit time actually pass from sender to receiver, accounting for errors — the information-transfer-rate framing used for BCIs, applied end to end. For current human systems it is minute: conscious phosphene-based communication runs on the order of a bit or two per minute (Grau et al.), and single-command systems convey roughly one reliable binary decision per trial (Rao and Stocco), with multi-brain systems only modestly better per decision.

The rate is bounded by the weaker of read and write, and both are weak: EEG decoding yields a few low-signal-to-noise bits, and a TMS phosphene delivers essentially one discriminable event. This is why demonstrations lean on pre-shared codebooks, redundancy, and slow signaling. Honest reporting counts only reliably transmitted, error-corrected bits — not the raw symbol rate — because uncorrected errors can drive the true mutual information toward zero.