Intelligence: Is It In The Brain Or The Heart?

Contrary to what we know now, the “organ of intellect” was not always known to be the brain. In fact, before the matter was settled, there were two competing views regarding where the intellect is in the body: the brain or the heart. The most famous of those on one side was Aristotle who was pushing for a cardiocentric (heart-centered) model, which argued that the heart is in fact the organ of intelligence (Frampton, 1991). In his observations, Aristotle noticed that poking the brain of an injured person did not induce pain. He therefore reasoned that the brain is not engaged in perception of any kind. Had he known about pain receptors, I’m sure he would’ve done a few more tests.

In addition, Aristotle noticed that the body grows cold when the heart stops beating, which led him to assume that the heart produces the body’s heat. To protect the heart from overheating, Aristotle assigned the function of cooling the unremitting heart to the brain. Furthermore, by Aristotle’s time it was known that human voice is supplied by air exhaled from the lungs. Hence, he reasoned that the heart supplies words and they come out together with voice as they roll out of the chest cavity.

The cardiocentric model of Aristotle’s went against the encephalocentric (brain-centered) model of his teacher, Plato, who said that the “eyes, ears, tongue, hands, and feet act in accordance with the discernment of the brain”. Although Aristotle’s cardiocentric model survived well into the Middle Ages, it eventually gave way to the encephalocentric model when Galen (the father of experimental physiology) showed experimentally the vital role of the brain. For example, cutting through the medulla, which is right above the spinal cord in the brain, can stop respiration. Those words coming from the chest as proposed by Aristotle were shown by Galen to require an intact brain to be able to be produced (Wilson, 2003).

This cardiocentric vs. encephalocentric historical narrative is how it is typically presented in the first chapter of a typical college neuroscience textbook. The professor will discuss this matter in class in a way that usually elicits a few laughs and raised eyebrows from the students as they wonder how ridiculous Aristotle was to think that the heart was the organ of intelligence and how silly his reasons for pushing a cardiocentric model were. What’s more surprising is how powerful Aristotle’s influence was, given that medical students were taught until the 16th century that nerves, like all veins and arteries, originate from the heart.

After everyone has their laugh at poor old Aristotle, the lecture will proceed to build upon the encephalocentric model and address different models of brain function and how the brain is studied. The heart will be relegated to the human physiology class and discarded as just a muscle pump that gets the blood everywhere in the body, never to be considered again as having anything to do with the mind.

Surprisingly, Aristotle may not have been completely wrong in his belief that the heart is an organ of intelligence. While it most certainly is true that  the brain is the major relay center for cognitive function, it seems that the heart is not just a muscle pump, as many believe it to be.

Your heart has its own nervous system that is composed of approximately 40,000 neurons. These neurons are connected differently and more elaborately than elsewhere in the body and while they’re capable of detecting circulating chemicals sent from the brain and other organs, they operate independently in their own right. Having it’s own “mini-brain” is the reason why heart transplants work, given the fact that severed nerve connections do not reconnect in a different body. Furthermore, this elaborate nervous centre in the heart has more functions than simply regulating the electrical activities of the heart to keep it pumping.

Dr. J. Andrew Armour is a neurocardiologist that has shown some fascinating facts about the heart’s nervous system. You can review his book “Neurocardiology: Anatomical & Functional Principles” if you’re interested in the technical details. For example, while the heart can be influenced by messages sent from the brain, it doesn’t necessarily obey it all the time. Furthermore, the heart’s “mini-brain” can send its own signals to the brain and exercise its influence on it. To give one illustration: oxytocin, which is typically referred to as the “love hormone”, has been shown to be released not only from the brain, but also from the heart. Oxytocin is not only important for love and bonding, especially for pregnant and lactating mothers, but it also has roles in social behavior, wound healing, learning, memory, and empathy. In short, it’s one hormone that affects a very wide variety of important functions.

Now it’s time to hold on to your seat and try not to fall over, because if you thought these facts about the heart are surprising, the following will probably make your eyebrows fly off your face.

It’s generally assumed that learning and memory are a central nervous system function. Meaning, this is a function for that organ inside our heads. However, due to some bizarre, controversial and anomalous observations, there is a growing push towards a systemic memory mechanism. In other words, not to limit intelligence functions to the brain. This came from observations in organ transplant patients – more specifically, heart-transplant recipients.

In a study from 2002, researchers from the University of Arizona and University of Hawaii collaborated to publish a paper titled “Changes in Heart Transplant Recipients that Parallel the Personalities of their Donors”. Ten recipients who received heart or heart-lung transplants underwent evaluation through a series of open-ended interviews. These interviews involved the transplant recipients, recipient families or friends, and donor families or friends, in hospitals in various parts of the US. Several parallels were being investigated including, changes in food, music, art, sexual, recreational, and career preferences, as well as specific instances of perceptions of names and sensory experiences related to the donors.

The interview transcripts are beyond astounding to read. There was a case of a straight vegetarian health-consious donor that turned a militant gay McDonalds-loving recipient into a straight vegetarian health food seeking person after the transplant. Another case was of a young donor who was a violin musician that made the older classical-music-hating recipient all of a sudden want to listen to hours of it after surgery. A third case was of a young woman who was a “hell-raiser” all of a sudden picking up her donor’s love for music and poetry. She was even able to finish the words to his songs, which she never heard before. A funny one was the 47-year-old man receiving the heart of a 14-year-old girl injured in a gymnastics accident. His wife commented at how he changed after surgery, “Gus is a teenager. No doubt about that. He’s a kid – or at least he thinks he’s a kid. Even when we’re bowling, he yells and jumps around like a fool. He’s got this weird laugh now. It’s a girl’s laugh and we tell him that. He doesn’t care.”

This study is only an example of many others. Overall, the researchers here found that on average, the recipients picked up two to five parallels per case from the ones they investigated. This is a very high transfer of personality traits that immunosuppressant drugs, stress of surgery, and statistical coincidence cannot explain.

All of us at one point or another have experienced situations where we mentally worked it out, and despite the calculations that show it to be a good thing to be involved in, something was off and it just didn’t feel right. Most of the time we realize that our “strange feelings” feeling, or “gut-instinct” was confirmed.

The human body is much more mysterious than reductionist science would like us to believe. While Aristotle’s cardiocentric view lost the battle, it hasn’t necessarily lost the war. Despite the importance of the brain, the heart seems to be serving as an organ of intelligence in its own right. There is an interesting difference in definition that seems appropriate to point out here. Intelligence is defined as the capacity for learning, reasoning, understanding, and having the aptitude in grasping truths and meanings. It comes from the Latin meaning “faculty of understanding, comprehension, and discerning”. Cognition on the other hand is the act or process of knowing and perception, and it comes from the Latin meaning, “a getting to know; acquaintance; and knowledge”. The definition implies that intelligence is a higher faculty than cognition, and the question that poses itself in turn becomes:

Is the heart our organ of intelligence, while the brain is our organ of cognition?

P.S. Although the study quoted above does include biases from the researchers involved, this is the nature of science as a whole. Every study has biases that speak of the researchers’ inclinations, and therefore when it comes to those studies dealing with something as subjective as personality and motivations, etc., the persistence of that element of subjectivity will guide how the objective results are interpreted. This article is not intended to completely negate or even reduce the importance of the brain. It’s just about looking at things from a different perspective. So if you’re a brain lover, breathe easy and remember how relatively young the field of neuroscience really is.

26 thoughts on “Intelligence: Is It In The Brain Or The Heart?

  1. Why so short !! Great article!! Scrolled up and down a few times to make sure I didn’t miss anything ! Love this article ! Amazing !

    Thanks for that!!

  2. Mashallah!Nice article. is there anything from the three Abrahamic religions that discuss this matter Akhi Mohammed?

    • Thanks. I can’t speak about the other 2 with any authority. But from an Islamic perspective, the centre of intelligence is in the heart, not the brain. In fact, and I’ll be writing about this soon, the language used in the Quran is in line with the difference between intelligence and cognition and it differentiates between the two organs as I’ve indicated towards the end of the article. Stay tuned ;)

      • Assalamu alaikum. Bro. Mohamed.I loved the article.Tabarakallah.I am waiting for your article elaborating the perspective from the Qur’an.Have you had a chance to write it yet?

      • Wa’alykoum As’salam Bro. Rafeeq,
        Alhamdulillah. I hope you found it as beneficial as you found it enjoyable. I’m still quite busy with a lot of projects on the go right now. I hope to write the paper on the Quran at some point during this summer insha’Allah. Please pray that Allah facilitates things for me.

  3. If people started to view intelligence as coming from the heart and cognition from the brain would that lead to ppl seeing mental illness differently? So many things to ponder.

  4. Masha’Allah, basically I am just a small time reader. Have read about cognitive then in my Uni. years and have also associates cognitive and intelligence as one. Hence the brain is the source of intelligence. Ever since I read the ayat that stating the heart is used for understand I begin to look for brain in the Quran. But I couldnt find any which points out to the organ rather points out the faculty of thinking, as an when “Ulul Albab” is mentioned. You are indeed a specialist on this subject if you do have the time could you be kind enough to extend this article and relate it to the ayat 7:179. JazakaAllah.

  5. Such an interesting article! Too short!
    Actually I am a medical student and I am studying right now about the heart. Professors told us that there were only 2 kinds of cell in the heart: cardiomyocytes (for contraction) and pacemaker cells (for the electrical activity). So I was quite surprised to read that there were neurons too! Can I please have the references for the studies on people who had heart transplantation? Thank you!

    • Hi Sharmila,

      You’d be surprised what else you’re not being taught by your professors!

      The titles of the study and book I’ve provided are actually linked direct to them. Just click on them and it will take you straight there. Let me know if it doesn’t work.

      • Thank you! And what you are saying is quite disturbing… it’s incredible that even in biology, students are not taught everything in an objective way…

      • You’re welcome!
        And yes… Sadly, not everything is presented objectively. What’s more disturbing is that students aren’t even aware of that and so they go out with a particular worldview that’s not representative of reality.
        My advice to you is after you finish studying, read and then read some more outside your assigned readings. Don’t limit yourself to what you’re being taught.

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  7. I wonder if there would be studies that will shed light to the difference in percentage of influence heart has on human intelligence between men and women! For some reason it occurs to me that women are more emotionally sophisticated than men, and this might suggest that their hearts play bigger roles in their worldviews. It would be interesting to come up with a way to test that!

  8. I believe this article is full of confirmation bias.
    Please review following rebuttal

    1)Not just heart, every organ is innervated by neurons; specifically, our GUT; it has complex integration of neurons; and operates independently on its own: therefore GUT is given its own name: The Enteric Nervous System. Can we say GUT has its own mini brain?

    2)You said heart neurons operates independently on its own; this is the reason heart transplant works; but we also do transplant for intestines; kidney; lungs; liver; and pancreas; they all work fine; in fact; kidney transplant works the best. Most organs can be transplanted; their transplantable attribute is not sufficient to give them title of mini brain.
    BTW, severed nerve connection do connect in different body; please research hand transplantation.

    3)You wrote “while the heart can be influenced by messages sent from the brain, it doesn’t necessarily obey it all the time. Furthermore, the heart’s “mini-brain” can send its own signals to the brain and exercise its influence on it.” This is not specific to heart; all organs follow this. All organs receive signal from brain; all organ send signal back to brain; all organs influence brain function through various hormones and negative feedbacks (example: adrenal gland) All organs control their own mini affairs on their own. These are foundation principle of medicine.

    4)Regarding your point on oxytocin; oxytocin is commonly synthesize and release by many organs: just to name few: testes, retina, adrenal medulla, placenta, thymus, and pancreas.

    5)As for transplant patient study; the subject participant were 10. Any study which such low participants is considered weak and statistically insignificant. Since it was a open-ended interviews; it open doors to so many biases. The hawthorne bias, pygmalion effect, and recall bias to name the few. Pygmalion effect occurs when a researcher’s belief in the efficacy of a study so much that he/she unknowingly affects the outcome of that study. The researcher of this study stated: He (Persall) became open to the possibility of cellular memory in transplant recipients partly because of his own bone marrow transplant in 1987, and also because of his Hawaiian heritage that has always valued the heart as being a “thinking, feeling, communicating, and spiritual organ”

    We have had million transplants; if 99% transplant patients didn’t feel changes in their personality, memory and behavior; but 1% did; we can’t say the 1% represent the general population. In my career; I have not met a single patient who reported changes in personality.

    In conclusion, numerous research shows brain as the center of intelligence and heart as a pumping organ with high sophistication.

    NN
    Cardiologist

    • Why call it a rebuttal and not a discussion. No need to be aggressive right off the bat :)

      1) You’re right. The heart is not the only organ innervated by neurons. I just chose it for this article. The gut is also a major neural neural centre and there is nothing wrong with calling it a mini brain for the gut. In fact, there is a whole field called “neurogastroenterology” that you might want to look into. Also, you might want to check out this article on the Scientific American titled “Think Twice: How the Gut’s ‘Second Brain’ Influences Mood and Well-Being” at http://www.scientificamerican.com/article.cfm?id=gut-second-brain

      2) Transplantation success is not the sole reason for calling it a “mini brain” of that organ. What interests me about the heart is its unique developmental time course in relation to the brain’s, and the specific neural activity it displays in comparison to other organs

      3) This is true. But it doesn’t negate what I said. If anything, it makes the brain less special.

      4) Again, correct, and also makes the brain less special.

      5) This is not the only study on this subject. I just happened to cite this one, but there are others that bring forth results that if we’re really being objective about it we would at least have a “well that’s interesting” type of reaction. Regarding your contention with statistics, I’m not sure how much basic research you’re involved in, but if you go to any lab meeting where they’re putting a paper together for publication you’ll find that one of the major issues discussed is which type of statistics to use. Some results are obviously significant, but others only become significant when one statistical measure is utilized as opposed to another. So in many occasions it really becomes a matter of who can argue their case better for which statistics method to use. Furthermore, the number of participants is not the only measure that is taken into consideration. If that is the case, then we would have to reject most research that uses animal models, which would basically be most medically related research. There are other measures that are taken into account such as the interactions between test condition and response, medical condition and response, age and response, etc. What they looked at in this study was the interaction between the personality of the donor and the recipient and the assessment of their relatives. Using the statistics method the authors of this paper employed, coincidence was ruled out. Lastly, you’re utilizing a genetic fallacy in order to discredit the findings reported by the author. It doesn’t mean you’re wrong, but it certainly makes your criticism weaker.

      Finally, appealing to your single career experience not having come across a single patient who reported changes in personality is not a measure to judge what others have reported. When I propose a theory in my field of research, I provide lines of evidence that others have found and use them as support. But if I can’t confirm other findings, which multiple labs have shown from multiple locations, it means either something is wrong in my experiments, everyone else is lying, or as I’m going to assume in your case haven’t actually done the experiment.

      Before I end this, you accused the article of being “full of conformation bias”. Is it possible that in your reading of it you were guilty of this very accusation? Because I could turn around and say that your whole comment was set up in order to confirm your own bias, which you stated in your conclusion.

      Mohamed Ghilan
      Neuroscience PhD Candidate

      • I called it rebuttal because it means to refute by evidence.
        Yes, I stated that the article is full of confirmation bias and your response has confirmed it. Also, it would be incorrect for you to say my reading of it is also guilty of confirmation bias.
        I’ll explain you why.
        Confirmation bias is when a person favors information that confirms his/her beliefs; so they gather information selectively and interpret it in bias way. In short, they select the information that supports their belief and leave out the information that refute their belief. I’ll give you an example of how you did it.

        Example: you wrote a persuasive not narrative article that heart encompasses intelligence. You operationally defined intelligence: the capacity for learning, reasoning, understanding, and having the aptitude in grasping truths and meanings.
        You support this claim by giving oxytocin (love hormone) example. “Oxytocin has been shown to be released not only from the brain, but also from the heart… it has roles in social behavior, wound healing, learning, memory, and empathy.” You try to show oxytocin is specific to heart and brain; thus; there’s similarity in their function. Although you know oxytocin is a common hormone released by most organs; you selectively chose to leave out that information to support your heart bias; this is called confirmation bias.

        In my responses; I never strategically selected information to support my bias; I just gave other side to our intelligent readers from whom you withheld information. For example: I informed them heart is not the only organ that release oxytocin; heart transplant is not the only transplant that works; severed nerve connection do connect in different body contrary to what you stated;

        Heart doesn’t have unique nerve innervation. It has sympathetic and parasympathetic innervation which is similar to other organs; adrenal gland has unique innervation; it is the only organ with preganglionic innervation. For your information heart unique developmental time course in relation to the brain has nothing to do with your argument; heart is not unique in its developmental time course; other organs also develop along with brain; you referenced a very weak study; when confronted you state that’s not the only study; well; then you should have referenced the strongest study. Yes number of participants is not the only measure taken into consideration but it is the MOST important measure. Out of 72 participant; 10 were selected; the researcher strongly believed in heart being the center of intelligence due to his Hawaiian background; researcher selected minimum two attributes to show there’s connection; it all adds to a very weak study.

        For your information; I have extensive research experience; I don’t think you know much about medical research; anytime medical or non-medical discipline studying a population; they randomly select participant from that population in large numbers; once the P value is less than .05 and standard deviation within limits; the study is repeated to establish its validity. As far as animal research goes; scientist aren’t studying population but particular physiology. In medical sciences; we can’t lesion the human frontal lobe to study its effect on rest of the organ; therefore, we can lesion a mouse frontal lobe; trust me; we study many mouse repeatedly.
        Also, most research are crap; thats why all medical schools spend a semester in training doctors how to filter between weak research study and strong one. Additionally, most physician have gone through publication process.

        Right now you’re neuroscience student; you don’t know the whole body; I studied the human body in depth as a whole not in section. When you study all the organs; you will learn that there is nothing special about heart to call it as the center of intelligence. When you read an article or research; you naively think it is specific to that section; if you understand the body as a whole you will be better equipped to filter bad information from good information. I understand you like to teach people what you learn; I admire it; but first you have to make sure you thoroughly understand the information yourself; additionally; when someone who knows the discipline in depth try to teach you; take the criticism constructively and learn from it.
        You other articles are good but this article was very misleading to your readers. if you knew the whole body; you wouldn’t have written this article.

        One request: you stated: from an Islamic perspective, the centre of intelligence is in the heart, not the brain. [I need a reference for this claim. Either reference Qur’an or Hadith]

        Thanks NN
        Cardiologist

      • First, your request for a reference is the Qur’an. There are many verses where it states the centre for intellect in man is the heart. In order to confirm that it’s not metaphorical, there is a very direct verse in Surah Al Hajj that says:

        “Have they not travelled in the land so that they should have hearts with which to understand, or ears with which to hear? For surely it is not the eyes that are blind, but blind are the hearts which are in the breasts” [Qur’an 22:46]

        Imam Ar’Razi in his magnum commentary on the Qur’an specifically addresses the issue of where intelligence lies, and he points out that many people consider the brain to be where it is, but that God clarifies that such is not the case. He also explains that this specific verse puts it in Arabic in such away in order for it to confirm that it’s not a metaphor. Imam Al Baiddawi also says the same thing in his commentary, as well as Ash’Shawokani, and As’Samarqandi. Interestingly, Ibn Attiya points out in his commentary that the physiological connection between the heart and the brain manifests itself in such a way that would make damage to the brain have a damaging effect on the heart. The only one that I’ve come across to try and divert the intellect back to the brain is Ibn Ashoor in his commentary, where he says the majority of commentaries are solely relying on language construction, but based on current scientific knowledge, one can say that the phrase “hearts with which to understand” could in fact mean that the hearts are a tool the the brain uses to receive nutrients in order to understand. However, Ibn Ashoor doesn’t reconcile that with how the verse explicitly ends by mentioning in a direct way that it’s the heart located in the chest where intellect lies.

        With this out of the way, I’d like to breakdown your “rebuttal” if I may:

        Confirmation bias is not restricted to how you defined it. Selectively choosing specific information while ignoring others is only one way to have confirmation bias. Another way, which is a bit more subtle, is to explain the available information in a biased way in order to confirm one’s beliefs. If we use the language of philosophy of science here, we call that “theory laden data”, which was explained by Thomas Kuhn in his book “The Structure of Scientific Revolutions”. In this particular circumstance, I worked with what we currently have for information. Namely, oxytocin has only relatively been recently discovered in other organs outside the brain and the heart, and in fact, whenever oxytocin is discussed, the overwhelming majority of the time if not almost all the time in fact, it is talked about as a neurotransmitter and discussed within the realm of neurobiology. In your response on the other hand, while you may not have strategically selected information, you’re still guilty of confirmation bias because you’re already coming at this topic with the bias that the brain is the centre of it all.

        Before I finish my response to you here, I’d like to pre-apologize if I’ll seem a bit aggressive. I don’t mean to be, but you’re very dismissive, patronizing, and offensive in how you respond, which is a trait I don’t have much patience for.

        Your understanding of statistics is quite primitive and reminds me of my second year undergraduate statistics course. This is confirmed in your fallacious notion that scientists don’t study populations but only particular physiology. Upper level statistics and design of the study is what makes our research relevant for populations. It seems like we have a bit of a misunderstanding or a miscommunication of some type, because you’re reading this article without understanding which angle I’ve taken with it. I could be wrong, and please don’t take this personally, but I find myself wondering if English is not your mother tongue. The reason I ask this is because of your poorly written responses and poor choice of words and overall sentence structure.

        For your information, my studies before embarking onto the PhD route were pre-medical, which include studying the whole body anatomically and physiologically starting from cell organelles and up to whole tissues and systems. Given that you sign off as a cardiologist, it would make your overall level of knowledge about the human body as a whole not that far off from mine. Let’s face it, you did a survey of anatomy and physiology and did your different blocks during your medical education but then went off into the specialization realm of cardiology. So you can’t speak as an all encompassing authority in medicine and patronize others in the way you do.

        I hate to do this, but you remind me of a statement I read in Robert Sapolsky’s book “Why Zebras Don’t Get Ulcers” where he says something interesting about medical practitioners, and it goes something like: “A physician can tell you that disease X is what you have wrong. But they can’t tell you why you have disease X”. The elaboration to this quote that really explains it is something one of my professors mentioned a few years ago: “Doctors are receptacles for scientists. Scientists figure out what’s wrong and why it’s wrong and how to fix it, and doctors identify that type of wrong a patient has before turning to the scientists to ask them for the cause and the fix”. Your job is restricted at looking at connections between various parts of the body and simple physiology. But higher level breakdown of the function of various aspects of the body is information you get from people like me who are in the background at the lab bench doing actual science.

        Your comment was not constructive criticism at all and therefore I do not accept it as anything valid to consider. You read the article with the expectation of a scientific review article where I would reference multiple studies and build a case that would contend with other theories in the scientific field. For that you can refer to http://www.pubmed.com . This article on other hand was addressed to the educated lay person who doesn’t get into all the technical details and study design analysis that you made the miserably failing attempt at.

        Sadly, you think most research is “crap”, because of a semester-long introduction to meta-analysis and statistics that couldn’t possibly be of any real significance to the development of a scientist or a critical thinker. All it did was make you arrogant, patronizing, and dismissive.

        Thanks for stopping by!

        p.s. my apologies to all doctors out there including my friends who are either doctors or in the process of becoming doctors. Obviously I don’t think of all doctors as I have described above. But this individual definitely fits the bill.

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