How did ancient people realize that the brain is the thinking organ?

With most other organs in the body, the function is fairly obvious: The eyes see, the mouth tastes and eats, the lungs breathe, the digestive system handles food, etc. But with the brain, how did ancient people realize that the organ inside the skull is used for thinking?) And when?

A lot of the time, they didn’t. IIRC, Aristotle thought that the brain’s purpose was only in cooling the blood.

But what evidence they could have used: The brain is close to most of the sense organs, in particular the eyes. And it’s easy to think of a person’s essence as being behind the eyes.

The head clearly houses something important, because serious trauma to the head is often fatal. Further, when it’s fatal, it’s very quickly fatal: A soldier who’s had his liver sliced open is probably going to die, but he’ll have a chance to tell you how much it hurts before he does. A soldier with his head smashed in (or even cut off) won’t do anything.

Head trauma, when not fatal, still often results in an impairment of cognitive abilities, or a drastic change of personality. This can especially be seen in deliberate lobotomies.

From Wikipedia: History of neuroscience.

However Alcmaeon’s views were apparently not widely accepted, and 150 years later Aristotle asserted that the heart was the seat of intelligence and the brain’s function was to cool the blood.

We have Egyptian texts dated to 1700-ish BC that study the effects of head trauma on the body’s neurological functions. They recognized that damage to the brain produced seizures, aphasia, and a lateral brain injury produced lateral symptoms. It’s not much of a leap to grasp that damage to the brain disrupts a person’s cognitive ability… Especially in an age when disputes were settled with blunt force trauma. This manuscript is thought to be a reproduction of an even earlier writing by Imhotep himself, which might date to 2800-ish BC.

Weirdly, this idea did not catch on all over Egypt. Other Egyptians wrote that the brain distributed blood and the heart was the seat of thinking and emotion. Oops.

Anyway… Alcmaeon of Croton (500-ish BC) is another good candidate. Imhotep wrote about the effects of head trauma, but Alcmaeon is widely considered to be the first to claim that thought and cognition reside in the brain.

See here:

It feels very obvious to me that my consciousness is located in my head. When I hear my inner voice, it seems to be coming from my head. My inner monologue coming from my heart doesn’t even seem to make sense.

Do other people feel this way naturally, or do I only feel this way because I grew up knowing that the brain is the seat of intelligence?

Pretty sure that’s learned. Even the concept of framing ones thoughts as an inner voice is probably cultural.

The brain being used to “cool the blood” isn’t that crazy an idea. There’s a lot of blood flow to your brain, and when you have a fever, your head gets hotter than (most) other places on your body.

And while severe head trauma will kill you very quickly, so will, say, a spear to the heart. So the heart as the center of consciousness also kind of makes sense. And your heart noticeably changes its activity when you experience strong emotion, so linking emotion to your heart makes sense. I’m not sure how the ancients considered thought vs emotion, but there’s not necessarily an obvious duality there, so it could be reasonable to consider them to both reside in the same place.

I agree with JB99 the clearest evidence that really isolates the brain as the seat of consciousness is that sometimes head trauma results in someone acting like a different person.

The fact that ancient scholarship didn’t catch on to the head being the seat of intelligence is fairly strong proof that people don’t automatically feel this way. And it’s rather difficult to set up an experiment giving any stronger proof than that.

How could they not? Well sure the eyes and ears are there, but our other senses are, at least to me, felt where they happen. So I see with my eyes, I hear with my ears and I itch with, right now, skin receptors over my right shoulder blade. Only having grown up knowing that it’s the brain that’s doing all the processing makes me think that’s where things are “really” happening, and even then it still doesn’t change that it feels like it’s my back that’s itchy, not like my brain is creating a sensation from nerve input from the periphery.

My point is that my brain could be elsewhere, with a broadband connection to the sensors in my head, and it would most likely “feel” the same, based on how I experience input from all the senses that aren’t sight and hearing.

Which is interesting, since the brain produces a disproportionate amount of heat. I’ve read from 20 to 25 percent of our calories are burnt there. But I’m not sure the ancients had any way to know that.

To be fair, Aristotle wasn’t the be-all and end-all of ancient neurological thought. In fact, his brain-as-radiator theory was pretty kooky even for his time. Many of his predecessors and contemporaries agreed that the brain was indeed the central organ of sensation and intellect.

Yeah, but sadly and despite getting all of his hypothesis about anatomy and biology out of his own read end (well, not just about that really), he was considered the scientific reference through Europe’s Middle Ages and beyond.

For science in general, maybe, but physicians had better and more specialized sources to rely on—Galen, for example, who was smart enough to dismiss Aristotle’s neurological notions as hogwash.

I always wanted to ask this question. When I want to “think harder” or at least mime it for the benefit of others, I grasp or massage my head.

Okay, that’s completely culturally learned. However, it seems to me, when I’m under strain, that strain is in my head. Ok, maybe my eyes go squinty and that’s the source of the strain.

What did ancient people do when they want to mime “thinking”? Very possibly they cover their heart, like we still do to make an oath. But has it been recorded that anyone, say in an Ancient Greek drama, clasped the part of his torso where his liver is found?

I once read an essay by Richard Feynman where he stated that in his opinion the feeling that the seat of consciousness was in the head was purely cultural. He further stated that he had trained himself to transfer the feeling of “centerness” to other parts of his body. Eventually he mastered the ability to redirect this feeling to outside of his body, which he believed was what was happening when people claimed they had experienced “astral projections”.

To quibble, I think it was more his philosophy rather than his hard sciences that the people of the Middle Ages looked to.

Another example from antiquity: In the Bible, Paul (or whoever it was who wrote the epistles) regards Jesus as being the head of the Church, as the head is the most important part of the body, and rules the other parts. That doesn’t explicitly say that the head does the thinking, but the implication seems clear.

You would think they would have figured it out rather quickly after having sustained any type of blow to the head? You don’t see stars when getting punched in the chest, stomach, or back. Give your head a smack and it does all sorts of crazy stuff to your thinking.
Headaches hindering thought processes would seem like a big clue also. Can’t think properly because your HEAD hurts.

And it didn’t just start with Paul: There are all the extended senses of caput in Latin; in Hebrew, ro’sh means both the head (in the anatomical sense), or the literal “top” of something, but also the chief or most important or the leader ("…for Hazor beforetime was the head of all those kingdoms"). And granted that if you stick a spear through someone’s heart, he’ll die pretty quick, it has nonetheless been known for a very long time that cutting off someone’s head–capital punishment–is a very swift and certain way of killing them. (It might take up to 15 seconds for a warrior to stop fighting–or at least thrashing around–after taking a weapon to the heart; sever the neck, and the rest of him will drop like a rock.)

I’m not totally convinced that the sensation of living behind one’s eyes is entirely cultural and learned, either. Our eyes are in many respects our primary sensory organs, which I think makes it pretty natural to feel like we live “inside our own heads” even if we know nothing of internal anatomy. And next in importance are the ears, which also reinforces the feeling. (I suppose a bloodhound might feel like it lived behind its nose.) Now, in one sense that’s just a coincidence: If our brains were in our armored thorax, and our “heads” were just a sort of sensory stalk, we might nonetheless naively feel like our consciousness was localized up there due to that cluster of sensory inputs, even if scientific anatomy told us otherwise. In a longer view, though, it isn’t just a coincidence that the primary nerve ganglion and the major sensory organs are all clustered together at the anterior end, and have been ever since the great-great-great…great-grand-mama bilaterian. If you imagine something like a flatworm, you naturally want your primary sense organs up front, so you can sense where you’re going, rather than in back, where you can only sense where you’ve already been; and that being the case, you’ll also want your “brain” (such as it is) close to those sensory organs so the inputs can be more quickly processed.

Do headaches actually hinder thinking more than other aches? It’s hard to think when you’re in pain, but I bet you’d have trouble thinking if you slammed your thumb in a door too.

And seeing stars could be explained by the fact that your eyes are in your head. Sure, your vision gets disrupted when you get hit in the head, because your eyes got bumped, and that’s how you see.

And you do see stars if you’re in enough acute pain because the shock response makes you faint, so even then the connection isn’t quite as clear.

A (vaguely) related question: Did people think that sleepiness/wakefulness resided in the eyes? Rubbing ones eyes when sleepy isn’t cultural; even newborns do it.

Slight tangent: I remember once seeing a TV documentary where they asked a number of people where in their body they felt it when they were nauseated. To me, nausea is absolutely unequivocally in my abdomen. But quite a few people said it was in their head. That was fairly shocking to me.

Huh, for me, nausea is mostly in the throat (more specifically, about where the throat joins the torso).