Cross-cueing
The way a split-brain patient can secretly pass information from one hemisphere to the other without the severed cable — by leaking it out into the world and back in. A patient might glance, touch one hand with the other, hum, or shift posture, so that the "mute" hemisphere's knowledge reaches the talking one through the body and senses. It is the standing caution on every split-brain result: an apparent transfer between hemispheres might just be the patient cueing themselves.
The transfer of information between the disconnected hemispheres by external or self-generated cues — eye and head movements, touching one hand with the other, subvocal counting, facial or postural shifts — rather than across the severed corpus callosum. Documented since Gazzaniga and Hillyard (1971), it complicates interpretation because an apparent inter-hemispheric "transfer" may be the patient routing information through the body and the senses.
Cross-cueing is the methodological conscience of this topic. Because a split-brain patient can leak information from one hemisphere into the shared world — a glance, a touch, a hum — and pick it up with the other, any finding that looks like preserved communication across the severed callosum has to rule out that the patient simply cued themselves. The caveat cuts both ways in the modern debate: Pinto and colleagues argue that cross-cueing is too loosely defined and too low-bandwidth to explain the unified, either-hand responding they observe, while defenders of the classic two-hemispheres reading invoke it to explain away exactly those results.