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Sick girl lying on the hospital bed and her mom kiss to support.

Can People in Comas Have Abstract Thoughts?

Neurosurgeon Michael Egnor discusses how we might test for that ability
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In the recent podcast, “Michael Egnor on Whether People in Comas Can Think,” Robert J. Marks raised an interesting point with neurosurgeon Michael Egnor: Can people in comas think abstractly or do they form thoughts only at a much more basic level, given how physically distressed they are?

The answer might surprise you. A partial transcript follows. This discussion follows on “Can loved ones in a coma hear us? Modern brain imaging studies show that very often they can. And, with help from new technology, they can respond.

08:52 | Detecting abstract thought in coma patients

Robert J. Marks: Let me ask you a question because we’ve talked previously about the difference between perceptual thought and abstract thought. In my mind, doing square roots is something like memorizing multiplication tables and such; it’s something you go to in your memory and it’s not true math. If you give someone a math problem they’ve never seen before, that would be true math. Is it possible to detect abstract thought in these patients or is everything perceptual? Or am I hearing you wrong?

Michael Egnor (left): Well, it’s tricky. First of all, one has to ask, what is the difference between abstract thought and perceptual thought? How would you define them? I think the point of cleavage is between abstract thought and concrete thought. The classic Platonic–Aristotelian distinction between abstract thought and concrete thought is that abstract thought refers to concepts that are completely divorced from any concrete object, whereas concrete thought is about a physical object.

A very good example would be thinking about the hamburger that’s sitting in front of you vs. thinking about nutrition. You can think about the hamburger—it’s a quarter-pounder, it’s got cheese, and it looks pretty good—and you can think about nutrition. It’s got a thousand calories and that would kind of blow your diet. Those are two different ways of thinking.

The problem for neurosciences, of course, is that we tend to think of these things together. That is, that, by and large, when a rational human being thinks about food, there’d be some abstract quality to it, like maybe I shouldn’t have that banana split right now. On the other hand, when you’re thinking about abstract things like nutrition, you’re likely, at the same time, thinking about concrete foods. Maybe at the same time as thinking about nutrition, you’re thinking “Maybe those fries I had last night weren’t the best thing for me.” So, neuroscientifically, it’s difficult to separate out thought about concrete things and thought about abstract things.

Robert J. Marks (right): And it would be very difficult, in the state of a coma, for a neuroscientist to differentiate between them.

Michael Egnor: I think that, for example, asking a question about square roots, there are a lot of abstract concepts there.

Robert J. Marks: Unless the patient is a nerd!

Michael Egnor: If they’ve just memorized the pictures; if they’ve just memorized what it looks like on a printed page, yeah.

Robert J. Marks: Yes, and again, I would refer back to the idea of memorizing multiplication tables and addition tables. And I think that a lot of people that do mathematics for living, like me, would have that at the tip of our fingers, not because of an abstract thought but because that’s what we do for a living and we’ve been there a number of times.

Michael Egnor: … I know, for example, that you personally have written extensively on Fourier transforms. Consider a person in Russia, who speaks no English whatsoever, who can know everything you know about Fourier transforms. And a person in China can know everything you know about Fourier transforms, even though nothing about your languages overlaps And you can imagine somebody who uses different symbols in their mathematics—but knows exactly what you know about Fourier transforms. So the knowledge you would share in common with somebody who does not share your language or symbols would be the abstract thought.

12:29 | Differentiating between abstract and concrete/perceptual thought

Robert J. Marks: Do you think that there might be a clever experiment, of the type that Owen generated, that would actually allow differentiation beteween actual or perceptual and concrete thought?

Michael Egnor: That’s a tough one. There are people who have looked at issues like that. Now, there are all sorts of ways of approaching it. I can think of at least a doorway into solving that problem of abstract vs. concrete thought so that it can be studied rigorously within neuroscience: Use Owen’s rather ingenious approach of scrambling the words in the sentences so as to remove the semantic content from the sentences.

For example, one could record the brain waves of a person looking at a word on a card. And let’s say that the word was “mercy.” And when you see the word “mercy,” it evokes thoughts about the abstract concept of mercy. You could take exactly the same letters and scramble them, so they don’t mean anything, and show the person the same card. So, for all intents and purposes, the person is still looking at a card that contains five letters in black ink on a white card. And the difference between the brain waves of the card that says “mercy” and the card that shows the scrambled letters would be the brain waves that correlated with the abstract thought. And if abstract thought is immaterial, then there should be a difference.

14:21 | Ways of assessing brain function

Robert J. Marks: Well you’ve kind of answered my next question. I think that most of Owen’s stuff was done in a functional MRI machine. Do you think that’s all required? The fMRI is going to be pretty expensive isn’t it?

Michael Egnor: Yes. The other way one could do it is with an electroencephalogram, with brain waves, where you put electrodes on the scalp. Or you could even do it during brain surgery with awake patients if the surgery is for some other reason and the patient consents to being part of a research project on mind states.

(A sundae might invoke both concrete thoughts [YUM!!] and abstract thoughts (“…but the calories”))

Robert J. Marks: While they’re comatose?

Michael Egnor: Looking at people who are comatose is just one way of getting at the issue but you could also look at people who are awake. The implication of this finding, I think, in comatose patients is that there is a disconnect between a mind state and a brain state that suggests that the mind state is not completely explainable by the brain state. But you can also look at that in awake patients.

15:37 | Implications on the treatment of humans in comas

Robert J. Marks: Do we conclude then that humanitarian treatment of those in deep coma should be to keep them alive, keep them going, keep them nourished , even though they have very little capability, possibility of being recovered?

Michael Egnor: Yes. It supports the basic notion that all human beings, regardless of their physical condition, warrant respect, warrant compassion, and have a basic right to certain fundamental things like food and water, hygiene, shelter, clothing. Just the basic ways you would treat any human being. I don’t think that people in comas should be considered less than human.

I wouldn’t treat a person who was in a coma with any less respect than I would treat a person who was sitting in a chair in front of me. I think, for example, that what was done to Terri Schiavo was a brutal, cruel thing. I should point out that, when she was deprived of food and water and it took her more than a week to die—they gave her morphine, which, you would think, if you really thought she had no awareness, why would you give her morphine? I think that even the people who were starving her to death were concerned that at one level she was aware. It was a pretty horrible thing.

Robert J. Marks: That’s an interesting observation. That their conclusion was actually self-contradictory to their treatment.

Michael Egnor: She was on a morphine drip during this. They gave her continuous morphine. I was at a medical conference during the time that she was being deprived of food [2005] and there was a discussion at the medical conference of the ethics of depriving her of food. Most people at the conference thought it was appropriate to deprive her of food. At least, most people who spoke up. It turns out afterwards, I found, a number of people didn’t think it was apprpriate but they didn’t really want to speak up.

Further reading on some of the unexpected (immaterial) ways our minds work:

Yes, split brains are weird, but not the way you think. Scientists who dismiss consciousness and free will ignore the fact that the higher faculties of the mind cannot be split even by splitting the brain in half. (Michael Egnor)

If your brain were cut in half, would you still be one person? Yes, with minor disabilities. Roger Sperry’s split-brain research convinced him that the mind and free will are real .


Four researchers whose work sheds light on the reality of the mind The brain can be cut in half, but the intellect and will cannot, says Michael Egnor. The intellect and will are metaphysically simple.

Show Notes

00:29 | Introducing Dr. Michael Egnor , Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook
00:58 | Can you still think in a coma?
01:14 | Definition of a coma
03:00 | The research of Adrian Owen on comas
08:52 | Detecting abstract thought in coma patients
12:29 | Differentiating between abstract and concrete/perceptual thought
14:21 | Ways of assessing brain function
15:37 | Implications on the treatment of humans in comas

Additional Resources

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Can People in Comas Have Abstract Thoughts?