Zaidel’s Metacognitive Dual Consciousness: Two Hemispheres, Two Minds

Neuropsychologist/cognitive neuroscientist Eran Zaidel proposes that phenomenal consciousness involves a metacognitive level of representation through which a cognitive system represents its own processing, and that each cerebral hemisphere can support such organization. His split-brain research challenges identifying consciousness with verbal report or a single indivisible self: the relatively speech-limited right hemisphere can perceive, understand, evaluate, and recognize itself. In his Closer To Truth interview, he combines this hemispheric pluralism with explicitly materialist and computational commitments, treating consciousness as graded and potentially realizable in suitably organized artificial systems (Zaidel, 2007).

Zaidel was a student of Roger Sperry and became a leading investigator of the disconnected right hemisphere, holding that each cerebral hemisphere is “an independent and complete cognitive system with its own sensations, perceptions, memories, language, personality, and consciousness,” and that the split brain merely exposes a duality present in everyone: “we are all split-brains some of the time, so we all have dual consciousness” (Zaidel, 2007).

Phenomenal consciousness, on his view, is a metacognitive level of representation, cognition about cognition, graded across species, separable from verbal report, and present in the speechless right hemisphere. Qualia accordingly need not be unified: the two hemispheres can have “different qualia” of the same stimulus. Zaidel embedded this in an avowed materialism, a capacity view of free will, and the conviction that suitably programmed machines would be conscious.

From Right-Hemisphere Language to Right-Hemisphere Mind

In Sperry’s laboratory, Zaidel devised the Z-lens, a contact-lens system that confines prolonged, freely scanned visual input to one hemisphere (Zaidel, 1973, 1975), and showed that the “minor” right hemisphere has substantial auditory vocabulary and some reading and syntax, though no speech (Zaidel, 1976, 1978). With Sperry and Dahlia Zaidel, he found that the disconnected right hemisphere recognizes self, family, pets, and public figures with “a characteristic social, political, personal and self-awareness comparable roughly to that of the major hemisphere” (Sperry et al., 1979), a result later echoed in “separate but equal” self-face recognition (Uddin et al., 2005).

These findings put Zaidel at odds with Gazzaniga, whose 1983 review concluded that right-hemisphere language and cognition are rare and largely a consequence of early left-hemisphere damage (Gazzaniga, 1983; Myers, 1984); Zaidel replied in the same volume (Zaidel, 1983a), and the Zaidel-Gazzaniga dispute over the cognitive capabilities and linguistic potential of the right hemisphere did not abate. The stakes were not only linguistic: Nobel Laureate John Eccles, who tied the unity of consciousness to language, “kept revising his definition of consciousness not to include [what] the right hemisphere can do” (Zaidel, 2007).

Two Complete Cognitive Systems

Zaidel treated each hemisphere as “a separate independent computer” that “works to some extent independently and sometimes interacts” (Zaidel, 2007). Experimentally, this became the contrast between “direct access,” in which each hemisphere processes its own input, and “callosal relay,” in which one merely forwards input to the other, a framework he carried from split-brain patients to the intact brain (Zaidel, 1983b; Iacoboni & Zaidel, 1996). Testing split-brain patients reveals “two different people in the same brain” (Zaidel, 2007). Unity, on this view, is a contingent achievement of interhemispheric interaction, not a given.

Qualia as Metacognition

Zaidel came to consciousness reluctantly, having once judged it “a pseudo-problem” (Zaidel, 2007). Testing criteria for a Martian organism, he argued that adaptive problem-solving, emotional prioritization, and a self-model can all in principle be programmed, leaving out qualia: “I feel pain now, I see red now.” This residue, he proposed, “is just a meta-cognitive level of representation where we don’t process information about the environment, or about decisions, but about the decision,” “as if we observe it from above. Not quite the theatre view of Dennett, but something like that” (Zaidel, 2007). Consciousness is therefore “continuous,” graded across species, and dissociable: its disorders “should involve some dissociation between what you do, and what you know about what you do.”

Do both hemispheres have qualia? “The evidence we have is that they do... and they sometimes have different qualia.” Shown an embarrassing image in the right hemisphere, a patient blushes and says “I feel embarrassed” but, asked why, “I have no idea”: an experience generated on the right and felt, without its content, on the left. Could the two have different qualia at once? “The answer must be yes... I see different colors in my two eyes. Why couldn’t I see different colors in my two hemispheres?” Because “qualia depends on prior experience and processing the information in the context of their whole organism’s history,” two hemispheres that prefer different dresses for the same dinner “must have different qualia” (Zaidel, 2007).

Consciousness Without Language

“I am convinced now that consciousness doesn’t require language.” Why? Because, he said, the right hemisphere has consciousness, and it doesn’t have language (Zaidel, 2007). A novice wine taster who can say “I like this one better” but has no word for why is conscious of the difference without verbal access. Conversely, processing need not be conscious. A neglect patient judges two drawings of a house identical yet prefers to live in the one not in flames; a split-brain patient’s right hemisphere failed a lexical decision task while its scalp EEG discriminated words from nonwords, in the gamma band, “often believed to be the consciousness frequency. And here it is associated with complete lack of consciousness” (Zaidel, 2007).

Materialism, Machines, Free Will

Zaidel affirmed that he believed in nothing “other than materialism” (“Absolutely”), conceding that being “completely comfortable is an exaggeration, but it is the best I can do” (Zaidel, 2007). By explicitly accepting a materialist account, he regards consciousness as graded rather than an all-or-nothing possession. He also accepts artificial phenomenal consciousness and that a computer could have qualia: “it’s just a matter of programming it appropriately,” since evolution programmed us: “What’s the difference?” The relevant organization includes adaptive problem-solving, affective priorities, self-representation, and the ability to represent one’s own cognitive states. Evolution’s construction of human capacities does not, for him, confer an exclusive ontological privilege over artificial implementation (Zaidel, 2007).

Free will is the biologically determined capacity to “modulate certain range of behaviors”; there is “a me in charge of [these] processes. But it’s all part of the same apparatus.” What happens if, as Zaidel argues, dual consciousness implies dual intention and dual responsibilities? Would we face the strange puzzle of how to punish one hemisphere? (Zaidel, 2007).

Assessment

Zaidel grounds claims about phenomenal consciousness in the experimental dissection of a speechless but self-aware hemisphere and treats unity as an achievement of interhemispheric interaction. His metacognitive account of qualia places him near higher-order theories, while his evidence for consciousness without speech challenges language-based accounts. An open question is how a speechless hemisphere’s metacognition is demonstrated rather than inferred from forced-choice responses, which Zaidel addressed by tying every attribution of consciousness to its mode of probing.

In summary, Zaidel’s distinctive contribution is the conjunction of metacognitive explanation and hemispheric pluralism: phenomenal consciousness need not be linguistic, indivisible, or biologically exclusive. The remaining challenge is to establish why the specified representational organization constitutes felt experience, and how independently conscious systems are individuated within an interconnected brain.

References

Gazzaniga, M. S. (1983). Right hemisphere language following brain bisection. American Psychologist, 38, 525–537.

Iacoboni, M., & Zaidel, E. (1996). Hemispheric independence in word recognition: Evidence from unilateral and bilateral presentations. Brain and Language, 53, 121–140.

Myers, J. J. (1984). Right hemisphere language: Science or fiction? American Psychologist, 39(3), 315–320. https://doi.org/10.1037/0003-066X.39.3.315

Sperry, R. W., Zaidel, E., & Zaidel, D. (1979). Self recognition and social awareness in the deconnected minor hemisphere. Neuropsychologia, 17, 153–166.

Uddin, L. Q., Rayman, J., & Zaidel, E. (2005). Split-brain reveals separate but equal self-recognition in the two cerebral hemispheres. Consciousness and Cognition, 14(3), 633–640.

Zaidel, E. (1973). Linguistic competence and related functions in the right cerebral hemisphere of man following commissurotomy and hemispherectomy [Doctoral dissertation, California Institute of Technology].

Zaidel, E. (1975). A technique for presenting lateralized visual input with prolonged exposure. Vision Research, 15, 283–289.

Zaidel, E. (1976). Auditory vocabulary of the right hemisphere following brain bisection or hemidecortication. Cortex, 12, 191–211.

Zaidel, E. (1978). The elusive right hemisphere of the brain. Engineering and Science, 42, 10–19, 29–32.

Zaidel, E. (1983a). A response to Gazzaniga. American Psychologist, 38, 542–546.

Zaidel, E. (1983b). Disconnection syndrome as a model for laterality effects in the normal brain. In J. B. Hellige (Ed.), Cerebral Hemisphere Asymmetry: Method, Theory, and Application (pp. 95–151). Praeger.

Zaidel, E. (2007). Interview by R. L. Kuhn, Closer To Truth, University of California, Los Angeles, April 2007 [transcript, Closer To Truth,]. https://closertotruth.com/contributor/eran-zaidel/; https://www.youtube.com/watch?v=Yef5gH45Dg4