Imagined Speech Decoders Perform Near Chance Across People in Three EEG Corpora
Researchers analyzed three public corpora to test whether imagined speech decoders trained on one person's scalp EEG could work for another. Across 482 ordered participant pairs, none remained significant after multiple-comparison correction; mean transfer accuracy was within 0.006 of chance in every corpus. A signal distinguishing the imagery task from pre-stimulus rest instead reflected a post-stimulus state. Only the competition corpus exceeded the within-subject threshold for every participant, but its frequency profile failed an artifact audit. The findings apply to these corpora and the representations examined, not to all imagined speech decoding.