Evidence record

What makes you one person?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

A judgement, not a fact: 12
Source checked: 45
Partly checked: 1
Presented as open: 1

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A scientific question with a philosophical core: whether cutting the corpus callosum divides a person’s consciousness. The page reports a real dispute between research groups and the field’s own statement that the evidence cannot yet settle it.

A split brain leaves either one subject of experience or two
Contested
The 2020 collective review suggests the answer may be neither a simple yes nor no, and philosophers have proposed partial unity or a non-whole number of subjects.
Behaviour in the laboratory can show how many subjects there are
Contested
Schechter and Bayne argue that unified responding speaks to unity of agency, not of experience.
Cutting the corpus callosum stops most direct communication between the hemispheres’ cortex
Established
Established for the cortex; routes below the cortex remain, and their role is one of the open hypotheses.

How the question is labelled

Claim: The single occupant

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own title. It frames the question the page leaves open, in claims 65 and 69, rather than answering it.

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: One person

Kind: Framing. Signposting. It asserts nothing a source could check.

The question

Claim: The brain’s two halves can be separated surgically.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Forty-five years of split-brain research and still going strongp. 653
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Philip Vogel and Joseph Bogen carried out a complete commissurotomy on a former paratrooper who was experiencing severe and life-threatening seizures
Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The term “split-brain” refers to patients in whom the corpus callosum has been cut for the alleviation of medically intractable epilepsy.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: What happens to the person afterwards has been described two opposite ways by careful researchers.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessAbstract; Introduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: This collective review paper aims to summarize the empirical common ground, to delineate the different interpretations, and to identify the remaining questions.
Supports
Split brain: divided perception but undivided consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.
Context
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The idea of split consciousness in a split-brain had its origin in the early split-brain studies (Gazzaniga, 1967; Gazzaniga, 1975; Gazzaniga et al., 1962; Sperry, 1968).

What this does not establish

The two accounts are the classic two-agent reading and the 2017 unified reading; the 2020 review adds that the answer may be neither.

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: Cutting the bundle connecting the hemispheres is done to relieve severe epilepsy,

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the corpus callosum has been surgically cut to alleviate intractable, severe epilepsy
Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The term “split-brain” refers to patients in whom the corpus callosum has been cut for the alleviation of medically intractable epilepsy.

What this does not establish

Says why the operation is done, not how often it succeeds.

Corrected

24 September 2026. Previously: “Cutting the bundle connecting the hemispheres relieves severe epilepsy and leaves the patient recognisably themselves.” The sources give relieving epilepsy as the purpose of the operation; none of them measures how well it does so.

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: and it leaves the patient recognisably themselves.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation
Supports
Split brain: divided perception but undivided consciousnessResults, phenomenal reports
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: they reported that their conscious unity was unchanged since the operation

What this does not establish

Rests on what patients report and how they seem socially; the review notes their everyday behaviour has not been observed systematically.

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Classic experiments suggested the operation produces two separate centres of awareness.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction, fourth and fifth paragraphs
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: This led to the hypothesis that there might be two separate conscious agents, a left hemisphere that is able to talk to us and can explain what it sees and feels, and a mute right hemisphere that cannot communicate in language
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: severing the corpus callosum seems to cause each hemisphere to gain its own consciousness

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: A 2017 study tested that directly in two patients and reported the opposite,

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessAbstract; Patients and methods
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.
Qualifies
Split brain: divided perception but undivided consciousnessPatients and methods, Subjects
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: For Experiment 1 we tested Patients DDC and DDV, for Experiments 2–5 we tested Patient DDC.

What this does not establish

Only the first experiment used both patients; the other four used one. The authors’ conclusion is an interpretation of performance, and is disputed (claims 44 and 46).

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026, split-brain or callosotomy with consciousness: Schechter and Bayne (2021) dispute how the 2017 result should be read (now on the page); no newer study of split-brain patients on this question was found.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: and the field’s own verdict is that neither result settles it.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The main issue concerns the first-person perspective of a split-brain patient. Does a split-brain harbor a split consciousness or is consciousness unified? The current consensus is that the body of evidence is insufficient to answer this question

What this does not establish

The verdict is a 2020 review written by twelve researchers from both sides; it is the field’s most direct statement, not a formal vote.

Later work looked for

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: The two halves of the brain communicate mainly through a bundle of fibres, the corpus callosum.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Forty-five years of split-brain research and still going strongpp. 653 and 655
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Severing the entire callosum blocks the interhemispheric transfer of perceptual, sensory, motor, gnostic ... In humans, a severed callosum precludes all such visual communication, even though the anterior commissure remains intact
Supports
Split brain: divided perception but undivided consciousnessIntroduction, first sentence
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: The corpus callosum is the main route for communication between both cerebral hemispheres

What this does not establish

Other routes exist below the cortex; claim 56 comes back to them.

Later work looked for

How the anatomy and the operation are described in the field’s reviews; not a finding later work revises.

Corrected

24 September 2026. Previously: “The two halves of the brain communicate through a thick bundle of fibres.” No source describes the bundle as thick; the sources call it the main route, not the only one, and the page later turns on the other routes.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: In the 1940s, and again from the 1960s, surgeons cut it to treat otherwise untreatable epilepsy.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Forty-five years of split-brain research and still going strongp. 653 and Timeline
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Van Wagenen and Herren introduced the concept of split-brain surgery in an effort to control the seizures of patients with intractable epilepsy ... Thirty years later, Philip Vogel and Joseph Bogen carried out a complete commissurotomy on a former paratrooper who was experiencing severe and life-threatening seizures
Supports
Forty-five years of split-brain research and still going strongp. 653
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Van Wagenen and Herren’s original patients were studied by A. J. Akelaitis at the University of Rochester in the 1940s
Supports
Forty-five years of split-brain research and still going strongTimeline
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: 1962–1967: Gazzaniga, Bogen and Sperry adapted the split-brain testing techniques developed in animals for use with the new series of split-brain human patients
Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Since the earliest reports by van Wagenen and Herren (1940) and Akelaitis (1941, 1943) on the repercussions of a split-brain, two narratives have emerged.

What this does not establish

The 1940s operations were partial and were abandoned because seizures did not improve, Gazzaniga writes; the complete operation dates from the early 1960s.

Corrected

24 September 2026. Previously: “For a period in the twentieth century, cutting it was a treatment for otherwise untreatable epilepsy.” Dated from the sources, and the implication that the operation ended with the century replaced by what the 2020 review says: complete split-brain surgery is rare now.

Claim 11 · checked 24 September 2026 · AI-assisted audit

Claim: The complete operation is rare now.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessWhat do We Need to Know?, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Full split-brain surgery is rare these days
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the number of split-brain patients is now rapidly decreasing, and it will soon be impossible to study this phenomenon

What this does not establish

Neither source gives a count; this is the researchers’ statement that few such patients remain.

Later work looked for

Europe PMC, 2021 to 2026, split-brain or callosotomy with consciousness: case reports show callosotomy still used for some seizures; no count of complete operations found, nothing that changes the claim.

Claim 12 · checked 24 September 2026 · AI-assisted audit

Claim: The patients went home and, by their own account and that of the people close to them, remained one person.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Yet, everyday experiences of the patient and their close ones suggests that only one person exists in a split-brain.
Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation

What this does not establish

Reports and impressions, not systematic observation (claim 27).

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Corrected

24 September 2026. Previously: “The patients went home, went back to work, and by every ordinary measure remained one person.” No source says the patients went back to work, and "every ordinary measure" claimed more than anyone has measured: the review says their everyday behaviour has not been systematically observed.

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: In the laboratory, something stranger appeared.

Kind: Framing. Signposting. It asserts nothing a source could check.

What the operation does

Claim: What the operation does

Kind: Framing. Signposting. It asserts nothing a source could check.

What the classic experiments found

Claim: What the classic experiments found

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: Flash a word to the left visual field, which reaches only the right hemisphere, and the patient says they saw nothing, because speech is usually a left-hemisphere function.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: when an object is presented in the left visual field the patient verbally states that he/she saw nothing, and identifies the object accurately with the ... left hand only
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the right hemisphere receives visual input from the left visual field and controls the left hand, and vice versa ... the left hemisphere is generally the site of language processing
Supports
Forty-five years of split-brain research and still going strongp. 654
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: In the vast majority of the population, the left hemisphere is dominant for language, and speech is generated only from the left hemisphere
Qualifies
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: when patients in earlier studies said that they saw “nothing” when a stimulus was presented in the left visual half-field, they may have meant that they could see it but that they could not identify or retrieve the name of the object

What this does not establish

The classic report. Later testing found the same patients can detect and locate a left-field stimulus; the review suggests "nothing" may have meant they could not name it.

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no newer data found; the 2020 collective review already records that patients can detect left-field stimuli they cannot name (in limits).

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: Ask the left hand, controlled by the right hemisphere, to point at what was shown, and it points correctly.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction, fifth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Now the patient, or at least the verbal left hemisphere, appeared oblivious to the fact that there had been a stimulus at all but was nevertheless able to select the correct object from an array of alternatives presented to the left hand
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: when an object is presented in the left visual field the patient verbally states that he/she saw nothing, and identifies the object accurately with the ... left hand only

What this does not establish

In the classic tests the hand usually chose from an array of objects rather than pointing freely.

Later work looked for

Claim 18 · checked 24 September 2026 · AI-assisted audit

Claim: Findings like this, accumulated over decades, produced the standard account: the operation leaves two systems that perceive, decide and act separately, and only one of them talks.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: This led to the hypothesis that there might be two separate conscious agents, a left hemisphere that is able to talk to us and can explain what it sees and feels, and a mute right hemisphere that cannot communicate in language
Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: decades of extensive research with a relatively small group of patients
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: severing the corpus callosum seems to cause each hemisphere to gain its own consciousness

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: The account is in the textbooks.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: although this clinical observation features in many textbooks ... the reported data are never quantitative
Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: these findings challenge the previously mentioned classic split-brain description, which is still found in reviews and text books

Claim 20 · checked 24 September 2026 · AI-assisted audit

Claim: The data behind it, the team that tested it again in 2017 pointed out, were never reported as numbers.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction, second paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: although this clinical observation features in many textbooks ... the reported data are never quantitative

What this does not establish

This is the 2017 team’s statement about the classic literature; the audit did not survey that literature itself.

Corrected

24 September 2026. Previously: “The account is in the textbooks. The data behind it were never published as numbers.” A sweeping statement about decades of papers rests on one team’s introduction, so it is attributed to them.

Claim 21 · checked 24 September 2026 · AI-assisted audit

The person is still one person

Claim: The person is still one person

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from what patients report and how they seem socially (claims 23 to 26); the next paragraph says what that rests on.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: Outside the laboratory these patients do not behave like two people sharing a body.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation
Context
Forty-five years of split-brain research and still going strongp. 657
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: of the dozens of instances recorded over the years, none allowed for a clear-cut claim that each hemisphere has a full sense of self

What this does not establish

Not systematically observed (claim 27).

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: They report feeling unchanged since the operation,

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation
Supports
Split brain: divided perception but undivided consciousnessResults, phenomenal reports
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: they reported that their conscious unity was unchanged since the operation

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: and they say they see the whole visual field and control the whole body.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessResults, phenomenal reports
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Both patients indicated that they saw their entire visual field ... they indicated that they felt, and were in control of their entire body. Finally, they reported that their conscious unity was unchanged since the operation (i.e. no other conscious agent seemed to be present in their brain

What this does not establish

The reports of two patients, the ones tested in 2017.

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: The exceptions reported are anecdotes from the first period after surgery, when a hand may act outside the speaking person’s control.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation
Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations, last paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: in the subacute phase following split-brain surgery the hemispheres are ineffective in communicating with each other. During this initial phase, phenomena such as an “alien hand” - that is a hand moving outside conscious control of the (verbal) person - may be present.

What this does not establish

The review calls these incidents anecdotal, and gives no count or duration.

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Corrected

24 September 2026. Previously: “In the weeks just after surgery a hand can act outside the speaking person’s control, and then that settles.” The review speaks of anecdotal incidents in the subacute phase, not "weeks", and offers the later settling as one conceivable account rather than a finding.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: What nobody has done is watch their ordinary lives systematically,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: although their extra-experiment behavior has not been systematically observed in great detail

What this does not establish

The review says "not systematically observed in great detail"; the page’s "nobody" follows it.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: so this rests on what they say and on how they seem in company.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 24 to 27.

Context
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Apart from a number of anecdotal incidents in the subacute phase following the surgery, these patients seem to behave in a socially ordinary manner and they report feeling unchanged after the operation

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: Any account has to explain both the laboratory results and the ordinary life,

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The review calls the gap between laboratory and everyday life a paradox that arose from the start.

Context
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The controlled lab tests suggested that consciousness is split in split-brain patients. Yet, everyday experiences of the patient and their close ones suggests that only one person exists in a split-brain.

Claim 29 · checked 24 September 2026 · AI-assisted audit

Claim: and the popular version of this story only explains the first.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The review says the two-agent picture is the one that captured the press, popular books and textbooks.

Context
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: It is especially this perspective that has captured the attention of the general press, popular science books and basic textbooks. ... Dominant in this description is the idea that in a split-brain each hemisphere houses an independent conscious agent.

Claim 30 · checked 24 September 2026 · AI-assisted audit

What it leaves

Claim: What it leaves

Kind: Framing. Signposting. It asserts nothing a source could check.

Whether awareness is divided

Claim: Whether awareness is divided

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: In 2017 a group tested two split-brain patients systematically, varying which visual field a stimulus appeared in and which hand or voice answered.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessPatients and methods
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: For Experiment 1 we tested Patients DDC and DDV, for Experiments 2–5 we tested Patient DDC.
Supports
Split brain: divided perception but undivided consciousnessPatients and methods
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: In all experiments the patient(s) responded with three response types (response conditions were blocked), verbal, right hand or left hand

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: If each hemisphere were a separate conscious agent, responses should have been accurate only when the responding side matched the side that saw.

Kind: What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction, last paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: can split-brain patients only respond to stimuli in the left visual field with the left hand, and to stimuli in the right visual field with the right hand or verbally?
Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the right hemisphere receives visual input from the left visual field and controls the left hand, and vice versa ... the left hemisphere is generally the site of language processing

What this does not establish

This is the prediction as the 2017 team framed it. Defenders of two agents reply that agents who cue each other would also answer from either side (claim 44).

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: They were not.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: split-brain patients with a complete and radiologically confirmed transection of the corpus callosum showed full awareness of presence, and well above chance-level recognition of location, orientation and identity of stimuli throughout the entire visual field, irrespective of response type (left hand, right hand, or verbally)

What this does not establish

Two patients in the first experiment, one in the rest (claim 40).

Later work looked for

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: Both patients detected and located stimuli anywhere in the visual field, with either hand and by speaking.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessResults, Experiment 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Both patients responded (nearly) perfectly in indicating presence of the stimulus ... and were highly accurate in indicating location of the stimulus
Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: split-brain patients can accurately report the presence and location of stimuli for any position in the whole visual field, with either hand, and even verbally

What this does not establish

Detection and location only; this is the one result from both patients.

Later work looked for

Corrected

24 September 2026. Previously: “Both patients responded accurately about stimuli anywhere in the visual field, with either hand and by speaking, while still showing the classic inability to compare across the midline.” Only detection and location were tested in both patients. Identification and the comparison across the midline were tested in Patient DDC alone.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: The patient tested further also identified stimuli that way,

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: split-brain patients with a complete and radiologically confirmed transection of the corpus callosum showed full awareness of presence, and well above chance-level recognition of location, orientation and identity of stimuli throughout the entire visual field, irrespective of response type (left hand, right hand, or verbally)

What this does not establish

One patient. Identification was well above chance rather than perfect, and better in one visual field or the other depending on the task.

Later work looked for

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: while still showing the classic inability to compare two of them across the midline.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessResults, Experiment 2
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: we found that he cannot compare stimuli across both visual half-fields (average performance 55.4% correct, which is not statistically better than chance performance

What this does not establish

One patient.

Later work looked for

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: The authors described it as divided perception with undivided consciousness.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessTitle; Abstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Split brain: divided perception but undivided consciousness ... These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: The detection task used both patients. The four experiments after it, on comparison, identity, orientation and location, used one of them.

Kind: Historical claim. A statement about the past that historical evidence can test.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessPatients and methods, Subjects
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: For Experiment 1 we tested Patients DDC and DDV, for Experiments 2–5 we tested Patient DDC.
Supports
Split brain: divided perception but undivided consciousnessResults, Experiment 2; Patients and methods, Procedure
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Patient DDC indicated whether two stimuli ... had the same orientation, shape or identity. ... Patient DDC indicated whether both rectangles had the same orientation ... Experiment 5 was similar to Experiment 1, except after each trial Patient DDC indicated confidence in his presence and location judgement

Corrected

24 September 2026. Previously: “The detection task used both patients. The four experiments after it, on orientation, identity and location, used one of them.” Experiment 2, the comparison across the midline, was one of the four and was left out of the list.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: That is a direct test of the standard account rather than a reinterpretation of old data,

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The 2017 study set out to test the textbook prediction quantitatively (claims 21 and 34).

Context
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: can split-brain patients only respond to stimuli in the left visual field with the left hand, and to stimuli in the right visual field with the right hand or verbally?

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: and it is two patients out of a population that is small and shrinking.

Kind: Present-day figure. A count, survey or report finding, as the named source gives it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: the number of split-brain patients is now rapidly decreasing, and it will soon be impossible to study this phenomenon
Supports
Split brain: divided perception but undivided consciousnessDiscussion, last paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: in a group of patients of which very few remain today
Supports
Split-brain: what we know now and why this is important for understanding consciousnessWhat do We Need to Know?
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Full split-brain surgery is rare these days

Later work looked for

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: The reading is contested.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Disagreement exists about the responsible mechanisms for this remaining unity.
Context
Consciousness after split-brain surgery: The recent challenge to the classical pictureAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: it is an open question whether the data presented by Pinto and colleagues is best understood in terms of the unity of agency

What this does not establish

Carried by the review; the Schechter and Bayne paper, cited beside it, was read only as its abstract.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: Volz and Gazzaniga argue that hemispheres separated for many years have had time to learn to cue each other, through small movements of the eyes or face, so answers that arrive unified need not come from a unified subject.

Kind: Hypothesis. A proposed explanation, not an established one.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: they may inform one another via strategic cross-cueing processes (Volz & Gazzaniga, 2017; Volz et al., 2018). The split-brain patients underwent surgery many years prior to testing, and the separated perceptual systems have had ample time to learn how to compensate
Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations, fourth paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: subtle cues may be given by minimal movements of the eyes or facial muscles
Supports
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground, last paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: One explanation could be that the split-brain houses two agents, each having their own experiences, who synchronize their behavioral output through various means.
Context
Split brain: divided perception but undivided consciousnessDiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Patient DDC and Patient DDV were operated on at ages 19 and 22 years, and were tested 10–16 and 17–23 years after the operation, respectively

What this does not establish

A proposed mechanism, not an observed one. It is reported here as the 2020 collective review, which Volz co-wrote, states it; the Volz papers were not read.

Claim: The 2017 team had tried to rule that out.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessDiscussion
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Another possible explanation to consider is that the current findings were caused by cross-cueing ... We deem this explanation implausible for four reasons. ... we explicitly set up the experiments to prevent cross-cueing

What this does not establish

The team argue against cross-cueing on four grounds; the review still lists it among the live hypotheses.

Corrected

24 September 2026. Previously: “” The page gave the objection without the 2017 team’s reply to it; both sides are now reported.

Claim 45 · checked 24 September 2026 · AI-assisted audit

Claim: Schechter and Bayne argue that even unified answers would show at most one agent, not one stream of experience.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Partly checked. Only part of the source could be read. What was not read is listed.

Supports
Consciousness after split-brain surgery: The recent challenge to the classical pictureAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: we argue that even if the behavioral data indicated that D.D.C has a unified consciousness in the agency-based sense of the term, it is difficult to reconcile them with the claim that his consciousness is fully unified in the experience-based sense
Supports
Consciousness after split-brain surgery: The recent challenge to the classical pictureAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: two conceptions of the unity of consciousness need to be distinguished: an agency-based conception and an experience-based conception

What this does not establish

Read as an abstract only. They also argue it is an open question whether the data even show a single agent.

Corrected

24 September 2026. Previously: “” The currency search found a published critique of the 2017 reading from the philosophical side; the page now names it.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: The same operation, two accounts

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: A word shown to the left visual field is denied in speech and pointed to by the left hand.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: when an object is presented in the left visual field the patient verbally states that he/she saw nothing, and identifies the object accurately with the ... left hand only
Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: Now the patient, or at least the verbal left hemisphere, appeared oblivious to the fact that there had been a stimulus at all but was nevertheless able to select the correct object from an array of alternatives presented to the left hand

What this does not establish

The classic finding, as in claims 17 and 18.

Later work looked for

Claim 48 · checked 24 September 2026 · AI-assisted audit

Claim: Classic reading: two awarenesses, one of them mute.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: This led to the hypothesis that there might be two separate conscious agents, a left hemisphere that is able to talk to us and can explain what it sees and feels, and a mute right hemisphere that cannot communicate in language

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: Both patients detect and locate stimuli in either field accurately, with either hand and in speech.

Kind: Experimental result. What an experiment or trial found, under its own conditions. A result in animals, cells or a simulation is not a result in people.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessResults, Experiment 1
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: we explored to what extent Patients DDV and DDC can detect stimuli across the entire visual field using three response conditions: left hand, right hand, and verbally. ... Both patients responded (nearly) perfectly in indicating presence of the stimulus ... and were highly accurate in indicating location of the stimulus

What this does not establish

Two patients.

Later work looked for

Corrected

24 September 2026. Previously: “Both patients report stimuli from either field accurately, with either hand and in speech.” Only detection and location were tested in both patients.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: 2017 reading: one awareness, with a gap in what can be compared across the midline.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: These findings suggest that severing the cortical connections between hemispheres splits visual perception, but does not create two independent conscious perceivers within one brain.
Context
Split-brain: what we know now and why this is important for understanding consciousnessCommon Ground
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Perception appears to be more split, while responding remains largely unified.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: Neither patient reports a second conscious agent in their brain or body.

Kind: Observation. Something measured or seen, as the named source reports it.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split brain: divided perception but undivided consciousnessResults, phenomenal reports
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Experiment
The source reads: Both patients indicated that they saw their entire visual field ... they indicated that they felt, and were in control of their entire body. Finally, they reported that their conscious unity was unchanged since the operation (i.e. no other conscious agent seemed to be present in their brain

What this does not establish

Two patients’ own reports.

Later work looked for

Crossref, 2020 on, "split-brain consciousness unity", and Europe PMC, 2021 to 2026: no systematic study of these patients’ everyday behaviour found.

Corrected

24 September 2026. Previously: “Neither patient describes or displays a divided life outside the laboratory.” What the 2017 paper records is the patients’ reports; nobody systematically observed what they display outside the laboratory.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: Whatever is split, it does not show in how the person describes themselves.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the patients’ own reports (claim 52) and says no more than they do.

Corrected

24 September 2026. Previously: “Whatever is split, it is not the person.” Stated as settled what the page itself calls open; narrowed to what the reports show.

Claim 53 · checked 24 September 2026 · AI-assisted audit

What holds a mind together

Claim: What holds a mind together

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: If unity does not depend on that cable, something else supplies it.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A conditional that introduces the review’s hypotheses.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Claim: Three candidates are argued over: information crossing below the cortex, one hemisphere driving the hand on its own side, and two separated halves that have learned to signal to each other.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations, first paragraph
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The first notion is that information is transferred subcortically. The second idea is that ipsilateral motor control underlies unity in action control. The third idea claims that information transfer is based on varies forms of inter-hemispheric collaboration, including subtle behavioral cues.

What this does not establish

The review calls the three not mutually exclusive.

Claim 56 · checked 24 September 2026 · AI-assisted audit

Claim: None of them is settled.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Disagreement exists about the responsible mechanisms for this remaining unity.
Supports
Split-brain: what we know now and why this is important for understanding consciousnessInterpretations
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Thus, the role of ipsilateral arm-hand control in explaining split-brain findings is currently not settled.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: Gazzaniga’s answer is that the self was always constructed rather than located.

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
Forty-five years of split-brain research and still going strongp. 658, end of Self-recognition
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Overall, the data indicate that a sense of self arises out of distributed networks in both hemispheres ... that sense of self is constructed by the left hemisphere interpreter on the basis of the input from these distributed networks.

What this does not establish

His argument from his own laboratory’s findings, not a result that settles the question.

Corrected

24 September 2026. Previously: “A fourth possibility is that the self was always constructed rather than located.” An unattributed "fourth possibility" set beside the review’s three mechanisms; it is Gazzaniga’s view and is attributed to him.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: That is not a dodge.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s judgement, which the next sentence gives reasons for.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: In his account a left-hemisphere interpreter builds a story about events that goes beyond the information it has,

Kind: An argument. An argument a named thinker makes. That it is made is checked; whether it succeeds is argued.
Review: Source checked. The cited passage was read, and it says this.

Supports
Forty-five years of split-brain research and still going strongTimeline
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Gazzaniga and LeDoux introduced the concept of a left brain ‘interpreter’, which creates a schema or ‘story’ about events that goes beyond the actual available information.

What this does not establish

A concept Gazzaniga and LeDoux introduced; the essay describes it rather than testing it.

Corrected

24 September 2026. Previously: “The left hemisphere invents explanations for actions the right hemisphere initiated, and asked why they did something, people in general produce a plausible theory rather than a report of the process.” Stated as fact what the cited essay presents as Gazzaniga’s concept, in words it does not use; and "people in general" went further than Nisbett and Wilson, who say reports are sometimes accurate. Both are now attributed.

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: and Nisbett and Wilson argued in 1977 that people asked why they did something often offer a plausible theory rather than a report of the process.

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Telling more than we can know: Verbal reports on mental processesAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: It is proposed that when people attempt to report on their cognitive processes, that is, on the processes mediating the effects of a stimulus on a response, they do not do so on the basis of any true introspection. Instead, their reports are based on a priori, implicit causal theories
Qualifies
Telling more than we can know: Verbal reports on mental processesAbstract
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in people · Review of the field
The source reads: they will sometimes be able to report accurately about them

What this does not establish

A 1977 review of experiments, arguing a position; the authors say reports are sometimes accurate when the real cause is also the plausible one.

Claim 61 · checked 24 September 2026 · AI-assisted audit

The uncounted

Claim: The uncounted

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: The half that speaks is also the half that explains, which is not an accident of anatomy but a problem for evidence.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Speech is left-hemisphere (claim 17) and so, in Gazzaniga’s account, is the interpreter (claim 60); the page’s point is that reports come through that one side.

Context
Forty-five years of split-brain research and still going strongp. 654; Timeline
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: In the vast majority of the population, the left hemisphere is dominant for language, and speech is generated only from the left hemisphere

Claim 63 · checked 24 September 2026 · AI-assisted audit

How many are in there

Claim: How many are in there

Kind: Framing. Signposting. It asserts nothing a source could check.

Claim: There is no agreed method for counting subjects of experience in a brain, intact or divided.

Kind: Open question. Something the page says is not known.
Review: Presented as open. The page says this is unresolved, and the review found that it is.

The review proposes new paradigms and asks what the crucial measures would be, which is to say none is agreed.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessConclusions
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: What are the crucial measures for unity of consciousness?
Supports
Split-brain: what we know now and why this is important for understanding consciousnessWhat do We Need to Know?
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: Clearly, the central question, whether each hemisphere supports an independent conscious agent, is not settled yet. Novel paradigms in this respect could lead to progress.

Corrected

24 September 2026. Previously: “Nobody has a method for counting subjects of experience in a brain, intact or divided.” Several methods have been proposed; what is missing, on the review’s account, is agreement on one.

Claim 65 · checked 24 September 2026 · AI-assisted audit

Claim: The dispute above is between careful researchers looking at the same kind of patient,

Kind: What scholars argue. A report of what specialists argue, or where they disagree.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessIntroduction
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: decades of extensive research with a relatively small group of patients
Context
Split brain: divided perception but undivided consciousnessPatients and methods
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026
The source reads: For Experiment 1 we tested Patients DDC and DDV, for Experiments 2–5 we tested Patient DDC.

Corrected

24 September 2026. Previously: “The dispute above is between careful researchers looking at the same patients,” The classic experiments and the 2017 study tested different patients, the 2017 ones in Italy.

Claim 66 · checked 24 September 2026 · AI-assisted audit

Claim: which is what it looks like when a question has no agreed measurement rather than no data.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s reading of the review’s consensus.

Claim 67 · checked 24 September 2026 · AI-assisted audit

Claim: Researchers from both sides of it wrote a joint review in 2020 and agreed that the evidence is not yet enough to answer it.

Kind: What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review: Source checked. The cited passage was read, and it says this.

Supports
Split-brain: what we know now and why this is important for understanding consciousnessAbstract; author list
Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Review of the field
The source reads: The main issue concerns the first-person perspective of a split-brain patient. Does a split-brain harbor a split consciousness or is consciousness unified? The current consensus is that the body of evidence is insufficient to answer this question

What this does not establish

Written in 2020; nothing found since changes it.

Later work looked for

Claim 68 · checked 24 September 2026 · AI-assisted audit

Claim: Until there is such a method, the number of minds in a split brain is a question about evidence for behaviour and a question about experience, and the two are not the same question.

Kind: This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review: A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Schechter and Bayne make the same distinction, between unity of agency and unity of experience.

Context
Consciousness after split-brain surgery: The recent challenge to the classical pictureAbstract
Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026
The source reads: two conceptions of the unity of consciousness need to be distinguished: an agency-based conception and an experience-based conception

Claim 69 · checked 24 September 2026 · AI-assisted audit

What was read

Forty-five years of split-brain research and still going strongGazzaniga, Nature Reviews Neuroscience · Publisher PDF posted on the author’s UCSB page (people.psych.ucsb.edu/gazzaniga/PDF/)Read in full, 24 September 2026 · Copyright; quoted briefly
Split brain: divided perception but undivided consciousnessPinto and others, Brain · Published version, UvA-DARE repository (pure.uva.nl/ws/files/21255810/Split_brain.pdf); Brain 140(5):1231-1237Read in full, 24 September 2026 · Copyright; quoted brieflyThe Supplementary material was not read.
Split-brain: what we know now and why this is important for understanding consciousnessde Haan and others, Neuropsychology Review · Europe PMC full text, PMC7305066Read in full, 24 September 2026 · CC BY 4.0
Telling more than we can know: Verbal reports on mental processesNisbett and Wilson, Psychological Review · Publisher scan posted for an MIT course (web.mit.edu/curhan/www/docs/Articles/15341_Readings/Social_Cognition/Nisbett_Wilson_1977_Telling_more_than_we_can_know.pdf)Read in full, 24 September 2026 · Copyright; quoted brieflyAbstract and statement of conclusions read for this page.
Consciousness after split-brain surgery: The recent challenge to the classical pictureSchechter and Bayne, Neuropsychologia · Europe PMC abstract, PMID 34371067Abstract only, 24 September 2026 · Copyright; quoted brieflyThe article is not open; only the abstract was read.