That claim does not seem to appear in the two sources he cites. The word subvocalize does not appear in Rayner.pdf) and appears only twice in Carver. Going by the titles, it would be rather surprising if it appeared in those sources. I’m skeptical enough of the usefulness of the claim that I’m not going to try other sources, but if someone gives me a precise citation, I’d be interested.
That claim does not seem to appear in the two sources he cites. The word subvocalize does not appear in Rayner.pdf) and appears only twice in Carver. Going by the titles, it would be rather surprising if it appeared in those sources. I’m skeptical enough of the usefulness of the claim that I’m not going to try other sources, but if someone gives me a precise citation, I’d be interested.