The Secret You

The Secret YouWith the help of a hammer-wielding scientist, Jennifer Aniston and a general anaesthetic, Professor Marcus du Sautoy goes in search of answers to one of science's greatest mysteries: how do we know who we are?

While the thoughts that make us feel as though we know ourselves are easy to experience, they are notoriously difficult to explain. So, in order to find out where they come from, Marcus subjects himself to a series of probing experiments.

He learns at what age our self-awareness emerges and whether other species share this trait. Next, he has his mind scrambled by a cutting-edge experiment in anesthesia.

Having survived that ordeal, Marcus is given an out-of-body experience in a bid to locate his true self. And in Hollywood, he learns how celebrities are helping scientists understand the microscopic activities of our brain.

Finally, he takes part in a mind-reading experiment that both helps explain and radically alters his understanding of who he is.

Watch the full documentary now

Ratings: 7.50/10 from 26 users.

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75 Comments / User Reviews

  1. Ryan

    I'll pass on this because of this

    "And in Hollywood, he learns how celebrities are helping scientists understand the microscopic activities of our brain"

  2. Waldo

    @ Ryan

    Suit yourself, but all it meant was they are measuring the reaction in peoples brains when they veiw a picture of their favorite celebrity, then loooking for the same reaction when veiwing things they may associate to this celebrity. In short they are trying to determine the routing of human thought, what part of the brain accesses what other part and how does this create consciousness. In fact thats what the whole program is about, what is consciousness and where/how does it exist. One of the best docs I have seen in years, thats why I recommended it to Vlatko. Thanks for posting this Vlatko, I am curiouse to see other peoples reaction to it.

  3. Agent Cooper

    This was brilliant, the question of what consciousness is and what makes us who we are is truly fascinating. Very interesting to see in witch way our consciousness differs during sleep, kind of explains why dreams can be so f***ed-up ... This documentary also touches the problem of free will, which I find both fascinating and scary.


    Good doc. if the last tests evidence is true......what an eye opener!

  5. Renate


    Passing on the hollywood mention is a mistake. They only mention that neurons are activated when people think about familiar thigs eg celebrities.

  6. solenoid

    I noes ! Enough Darwin, Galapagos and apes already. I WANT Cosmos documentaries! :)

  7. siddartha guatama

    This is an incredibly fascinating documentary - so much so that I could only watch just over half of it (I stopped at the point where Marcus travelled to Sweden to see Henrik Erikson) - because my brain could not take any more information in!
    I really need to think very carefully about what I have seen so far. I was 'hooked' from the moment Marcus explained about the time when (on a train between Paddington and Oxford) he suddenly had a 'FLASH' of realisation - and the subsequest solution to a problem that he had been pondering for ages.
    How I 'connected' with his words! reminded me of the first time I meditated (I mentioned this before) - as I got the 'flash' it buzzed me out of my meditative state! - it was (I think) the realisation of conciousness (as Marcus said)
    Again, I agree with so much of this documentary - he says that there is no equation to explain conciousness, but the 'mirror' test proved that between 18-24 months is the time when humans become aware of the 'self'
    and 'death awareness' is the price we pay for 'self awareness' - gosh this is mind boggling to me, and yet it all fits into place in my mind.
    100 billion nerve cells in the brain!- 100000000000 - thats an incredible amount, and this man put himself through 'sedation' by way of anasthesia to contribute to trials on the constant activation of the cortex - conciousness. they said that there is 'no magic conciousness meter'!!) and that 'interaction is the only way'
    yes, the 1st half ended with references to Descartes - the French philosopher who made ground breaking claims of 'dualism' - ie that the 'body and soul' are seperate entities - that the soul can exist - and yet remain seperate to the body.
    Im not sure about THAT! - I am not even sure if I have a soul....but I know I have a body because I can see it.
    I thououghly enjoyed the first half - its made me think so hard Ive got a headache now - but I will think things through ( I made notes to help me) and I will watch the 2nd half tomorrow
    BRAVO - thank you Waldo and Vlatko (for some HEAVY stuff man!)

  8. Waldo

    @ Sid

    The reference to Descartes was indeed pertaining to his work on the soul, and whether it exists. That was my main facination with this doc., the question of do we indeed have a soul, not so much in the religiouse sense but a seperate entity that is us devoid of physical form. If so how does it experience the physical world, obviousely through our five senses for one. Marcus demonstrates at one point in the doc that if your sense of sight tells you that "you" are here then that is where "you" are- so to speak, no matter where in physical reality your body is. Its facinating to see how we can trick our sense of self into thinking it exists here or there when in reality it is somewhere totally different. But that is not all of what constitutes the "I" in us all, our physical or sensed location is only a small part of a bigger whole. Our brains are constantly responding to simuli that we hardly notice and through the interpretation of this stimulus building what we call reality around ourselves.

    This is truly a facinating documentary, I hope you all enjoy it as much as i did. If nothing else it will make you ask questions that may lead you to a whole new perspective on what reality really is and how the "I" in us all experiences that reality.

  9. Racheal

    Really interesting!!

  10. Immortal

    Really enjoyed this doc, thank you very much for posting.

  11. Eric

    Really interesting doc.
    I practice out of body experience since i have 12 and i really like to know whats happen in my brain during these experiments :)
    The last part of this doc is really surprising, but i think the 6 seconds are relative to what we are doing. Probably, sometimes its 2 seconds, or another time the unconscious and conscious mind are totally balanced and respond at the same time. But i firmly believe our unconscious mind have the total control of our action.

    Very profound subject, but so interesting and so us :)

  12. Wyatt

    Legalize the herb!!!!!!!

  13. Slah

    "The only compelling evidence for self-awareness is in humans and the great apes."

    The experiments with dolphins, elephants and magpies in mirror tests showing they have self-awareness seem pretty 'compelling' to me. Did this show do its research?

  14. manoulo

    Fascinating vid. I would love to see experiments with the artificially induced out-of-body experience taken even further. Plenty of possibilities.

  15. Toast And Marmalade

    Well that was ever so slightly epic. This documentary is fascinating and stays true to the brilliance of Horizon. However, although he makes perfect sense talking to the camera, the way in which he interacts with those on screen (even when not under the effects of drugs or optical illusions) is a little bizarre. It’s easy to tell that he comes across, to say the least, peculiar. The look bell gives him in 3/4 is awesome, she keeps smiling with a "WTF" look in her eyes XD
    It’s always so enjoyable to watch someone so excited about what they are exploring and explaining to the viewer that they don’t quite have the time to let anyone else in on the secret at the time they’re shooting the documentary.
    I do wonder how long it will be before we as a species really understand the complexities of human interaction, with both the external and internal worlds we experience with one mind.

  16. Achems Razor

    That is the true mystery, what is consciousness? is everything but electrical impulses to the brain, everything we see, hear, and touch, are nothing but electrical impulses, and in our brain they are converted into our reality, but what converts what? does our reality make us? or do we make our reality?

    @Toast And Marmalade: mentioned "both the external and internal worlds" I personally think everything is internal, Via our invisible movie screen in our mind.

    Another excellent doc. on this subject is..."Primacy Of Consciousness" on TDF

  17. capricious


  18. afly_on_the_wall

    I'd like to see these consciousness tests done on a Buddhist monk. now that would be interesting :-)

  19. amar

    there were some studies done already on the monks, they show a large area of prefrontal cortex compared to a a normal guy. In fact they have scanned some monks for a period of time and observed the effects of meditation. the results show that there are changes in the physiology of the brain, especially the enlargement of prefrontal cortex. preforntal cortex is where the high level stuff happens like thoughts etc. perception leads to consciousness in all of us but these cognitive stuff seem to make us even aware of what we cant perceive.

    P.S. FYI,I am a research student in neuroscience :-).

  20. Steve Baker

    Did I just watch this or was it only a figment of my imagination?

  21. Abrahams Son

    Sometimes a cigar is just a cigar.......

  22. Waldo

    @ Abrahams Son

    You said: "Sometimes a cigar is just a cigar……."

    Which implies that at other times it is not a cigar. Are you insinuating that it is infact you that has the definitive final say on its existance or lack thereof? Is it not possible that to you it is a cigar, but to me it is the center post of a Centrifugal Bumble-Puppy apparatus?

  23. yoserian

    would somebody be kind anough to post a link or reference to the last experiment?

  24. John

    Awesome documentary!
    I'm glad my neurons decided to press

  25. Toast And Marmalade

    @Achems Razor
    you say that you think everything is internal. From the veiw point of the self, I do beleive it is. However, when outside causes effect our life, for example the enviroment, would you not say that is experiencing an external world to the relms of our consiousness?
    eventhough each individual may react to it differently and percieve it on an individual peronal level, it would be the same external force they are experiencing.

  26. Achems Razor

    @Toast And Marmalade:

    Don't know the answers, all I can give are conjectures.

    Maybe everything is gestalts of consciousness. For one thing, matter is illusion, an atom is 99.999% empty, an atom can also be in more than one place at a time, (many worlds theory)

    According to QM even time and space are illusions.

    Do we form the reality, make matter where non exists? according to many top physicists, that is to the affirmative.

    Google..."youtube-a conscious universe-the observer effect"

    By our observation do we collapse the wave form? Google..."Copenhagen Interpretation"

  27. Abrahams Son

    Waldo, yes I am and no it is not.

  28. Waldo

    @ abraham's son

    Well, as long as we got that cleared up. Good luck with that then.

  29. Bryan

    I think, therefore I think I am

    Why does a dog lick its' balls?

  30. plato

    bryan, because they are

  31. plato

    What caught my attention-mainly-was the fact that the brain knew the switch he was to press, 6 seconds Before he actually did…mindboggling!

  32. Sal D

    it was well done, and very similar to a Special Edition of The Discover magazine titled "The Brain" almost identical.

  33. Epicurean_Logic

    This is a cool documentary that hopefully clears up a lot of the pseudo-scientific mumbo-jumbo that is invariably associated with any discussion involving the word consciousness!

    A lot of interesting experiments, not-the-least in moving Marcus' awareness out of his body and into the body of the someone else. Cool stuff!

    Marcus is a bit arrogant though; his monologues are littered with 'I did this' and 'I did that', maybe that’s the curse of the maths nerd. I prefer to see Marcus sticking to his field of Prime number research and not dabbling with the applied world of experiments. But hey, we all have our hobbies.

    A salty dogs ball licking 8/10 from me.

  34. ReligionIsntAllBad

    I love the guy who not only passed up watching the docu based on one phrase in the summary (which it turns out he misinterpreted)... but then admitted how ignorant he was in the comments! Thumbs up, Ryan!

    I was absolutely impressed by the first 2 parts of this documentary. Marcus seems to have a completely unbiased viewpoint on consciousness so far. He is just questioning its nature in a very straight up easy to access manner. He has not espoused any religious beliefs about consciousness, but simply is seeking to understand the nature of the self through modern, Western terms. In addition he just seems like a really nice guy, for whom I would buy a pint should we ever meet.

    Cant wait to finish this docu when I have a bit less work.

  35. ReligionIsntAllBad

    Ah OK ... Marcus is himself an atheist, which he does not attempt to conceal ... it just doesnt happen to come out till the very end of pt 2

    What I think is most important, is that Marcus and many of the scientists featured in the docu, are making clear distinctions between the subjective and objective worlds: the subjective (or inner) world of ’I’, and the objective (or outer) world of ’it’.

    Personally, I would like to see science attempt more and more to tackle the subjective world of inner consciousness to the best of its ability. Testing Marcus is interesting, but how about testing the consciousness of tibetan buddhists in various meditative states. Perhaps we should be putting spiritual adepts to the test and challenging their and our own ideas of the self.

    Great docu!

  36. Fin

    How do you determine the qualitys of mind?

  37. billy ryder

    Why are you, you, instead of some dude from 1765? Why are you, you now and not at some other time in the future? This documentary answered the Who is I? Now for the why are you "I"?

  38. Just Erica

    I really don't understand athiesm - It is clear that there is a higher power at work. God has given us free will but at the same time has a perfect plan for our lives. 6 seconds... if the doctor can see it before we consciously make a decision then God definately can trump 6 seconds.

  39. DM-trip-tamine?

    I dont think any discussion of consciousness is complete without a discussion of DMT. I would like to have seen what his brain patterns did in the machines after a big hit of the tryptamine...

  40. Jimmyh2o

    The brain doesn't produce consciousness, it's receiving it. A better question is how are we able to be conscious of thoughts and thinking of consciousness simultaneously? Awareness is key. It all occurs in the field of awareness. Not awareness as in "to be aware", but awareness as a noun. Like gravity is a noun, but awareness is immeasurable and intangible. It is ultimately the only thing that is aware of everything and of itself. This is how we have to capacity to hear thoughts and be conscious of the "I" who heard it. We are, and everything is, simply expressions of awareness itself.

  41. LMFAO

    Amazing doc, this marcus dude is a science documentary hero! Everything he touches turns into proof LOL. His philosophical state really tickles my mind

    Anyone knows more documentaries done by this dude? I have seen the math docu, the one with the comedian learning math and the one were the comedian tries to measure a string

  42. Soeren

    very interesting documentary, it is far the most mind tricking one i have ever watched, and like many other here, it twists and bends your mind, and its hard to perceive all this information and understand it.

    HOWEVER, i dont think this documentary disproves the whole soul thing, far from. especially if you watch documentaries, that take on the soul question from a scientific view, like this one does (but with another outcome), and i think these shows are just as convincing as this one, which just makes my head hurt even more, cause what am i going to think, when both sides have great arguments.

    also like the guy/girl 2 post above me mentions DMT, i think it is very relevant to this matter, and i will definetely one day try DMT, for the sole purpose of exploring my mind/possible soul, and i think that if you like this video, you should definetely watch DMT - The Spirit Molecule, it is just as interesting, if not more, cause who doesnt like the idea of 'you' floating around out there in another dimension and then start a new life. also im not religious, which i bet most of you agree on, that you dont have to be, to believe in souls

    Just Erica: no it is not clear at all that there is a god, bible quotes, other ancient texts, the sensation of a godly pressence, pressence of ghosts can actually be explained, i dont remember which docu i saw it in, but it was about ghosts. it is too naive to jump to the conclusion that there must be a god, when you (nor do i) dont understand how complex the mind is, nobody to this date understands the human mind, so dont jump to conclusions.

  43. jackie

    im a 19year old girl who has questions!!

    how would you know which senses are stronger. What if you were trapped in a giant freezer and you wore that head set that made your eyes believe you're in a room filled with snow.

    But then in reality the room starts to get hotter and hotter, would your mind believe that the room is still cold or would your other senses kick in telling you that the room is hot? could you trick your mind to close off all the other senses and just believe what your eyes show you? then would that be a type of outer body experience?

    and if you did believe what your eyes show you, do we just make an illusion of what we see? how would we be able to tell what is reality or not reality?

    If the Tibetan monks had such large prefrontal cortex because of meditation, would they be smarter than a person like Albert Einstein?

    what is knowledge? is knowledge wisdom or does knowledge deal with memorization?

  44. whatisknowledge

    @jackie: knowledge is not merely the passive memorization of information as it changes our memory framework in the same way that water erodes limestone, and determines the classes of detail that will be most easily absorbed and understood in the future. this knowledge of knowledge is wisdom.

  45. jackie

    @whatisknowledge and @ReligionIsntAllBad

    Thank you for the help! It brought me greater understanding of who "I" am. I feel happy! thanks!

  46. Karen

    Psychology is very interesting that is why I have a degree in it. For those of you who found the topic of consciousness interesting you will be happy to hear that this documentary comprises about a 1 hour lecture in the consciousness course of whole. So if this blew your mind 'you ain't seen nothing yet'! There have been hundreds of experiments that have wielded a bunch of these factoids that make you go hmmmm.

    The time delay and the lighted up parts of the brain that was being observed to coincide with it, are the areas that are involved with memory and the memories associated to that particular stimulus. The more associations the longer or shorter duration it would take to make a reaction [decision] depending on if the experiences were negative or positive or equal in strength, a threshold has to be surmounted. Or in other words brains cells were being activated, turned on and some were purposely off. Our brain is binary but also encompasses systems and processes. To answer the girl with the questions, sometimes you could be deceived [tricked] but sometimes you would definitely be able to tell the difference. Perception is realized in the brain not the eyes or ears or nose or by touch, those are the things that enrich our experiences. By definition to be really alive you would have to be aware, other wise you would be in a mental state.

    I am not buying into the theory that other animals are unaware of their own presence. Maybe this is just not the right test. And I am sure another experiment of a different type could easily put this theory into question. Anyone who has lived with a cat would agree with that, they don't freak out when they see an image in a mirror, they recognize what it is! And I would also argue that animals are conscious of time. There is also the other factor of frequency in how an animals eyes perceive light in general, and that all are not equal or similar. All that this experiment suggests is that the brains of humans, apes, and chimpanzees have a developmental period in which self perception is something we grow into. The 'I' is a composite of memories and experiences influenced by heredity and environment, that is why we are all unique, but the free will part is debatable.

    Hasn't it been said that knowledge is knowing information and wisdom is the application of knowledge. By the way, our brains constantly recirculate information. It is a motor that constantly runs and being busy is a requirement. So...garbage in garbage out. Drugs only stimulate or depress the brain.

    I do not think the brain is receiving consciousness, but like it was stated it is enmeshed with the mind. It seems to be more of a by product or an entity of it's own.

    There have been many people who have tried to explain consciousness but to date it is an unsolved mystery, we can only speculate because there is no definitive proof either way and if you can solve this conundrum of the 'ghost in the machine' you will be very rich. No body knows the secret to life. I hope that consciousness will not equate into a math mathematical formula, that would be as depressing as finding out our genome wasn't very large.

    And you thought Psychology was just about Freudian analysis, LOLOLO

  47. Achems Razor


    Good blog, have read with interest, and agree with what you have said,
    Especially "self perception is something we grow into" as is proven with babies. But, I think comes from the collective consciousness being instilled to the baby. (parents etc:)

  48. Epicurean_Logic

    @Karen. Fascinating stuff. When you have the time could you please expand on and develop some of the ideas that you stated. In particular,

    'All that this experiment suggests is that the brains of humans, apes, and chimpanzees have a developmental period in which self perception is something we grow into. The ‘I’ is a composite of memories and experiences influenced by heredity and environment, that is why we are all unique, but the free will part is debatable.'

    I like how Phycology/neuro-science comes back full circle and touches on philosophical questions - 'the free will part is debatable' - it is refreshing to see that the modern sciences cycle back to questions asked by related and preceding disciplines.

  49. Dildo The Elder

    The white haired one is the Hill! Its hilarious whence in the catscan trippin ballsacks yallsaks.

    Only pensilvanians would ever agree with stuff like thort. Even hungry men shouldnt eat apples.

  50. Hugs

    If my "I" was really separate from my body, drinking alcohol could not change the way "I" function, i.e. the soul cannot be separate from the body.

  51. smugg

    wow, scientific approach to ayahuasca !!!

  52. Damon Rolnick

    the soul is the awareness that "i am"

    not the body that is

  53. wpsmithjr

    @Karen, I agree with you on the question of whether or not animals have a sense of self... they do. It's rather arrogant to think that we're the only living creatures on earth intelligent enough to realize we exist. That idea is ludicrous in my humble opinion. Does an animal not know when it is hungry? Does it not feel pain? Does it not have all the same senses that we have that give us information about our environment? Even animals who can't tell they are looking at themselves in a mirror will try to play with or attack the image as if they think it is another animal. So, they not only realize that they exist... but they realize other animals exist too.

    My question is, how do you define "free will"? If our choices are made as a result of the unconscious mind and the conscious mind both, and they are affected by our experiences in the past (which gives us information with which to make our decision), then who is to say that we had a free, conscious choice and we made that choice based on our experience... or if our choice was inevitable due to a building of a neural network in our brain which was simply a result of our biological life on earth. AND WHAT IS THE DIFFERENCE, REALLY? I can't see much of a difference between fate and freedom. It's all the result of a choice. What's a "choice" anyway if everything is already pre-determined? If we're drones simply running through a systematic, scientific, pre-determined life, then how do we have the concept of "choice" to begin with?

    Am I making any sense?

  54. Guest

    these are in a backward order, from last to first.

  55. All WorldEarth

    @wpsmithjr- conclusions from facts are not arrogant, humans are the only creatures we know that has a sense of self. Reacting to its own image proves that it does not recognize itself but is guided by animal instincts, the same as its hunger or fight/flight mode. Animals do not posses free will, only humans do.
    I have made the conscious choice to write this comment, it was not fate or predetermined. I set my dinner aside to do it which goes against my hunger instincts. An animal will not set aside its food when it is hungry and convey thoughts in order to point out fallacies in another animals logic because they dont use logical thinking.

  56. Stephen W.

    Humans are not the only animals that possess a sense of self. The great Ape as well as Cetaceans all have a sense of self. As for free-will, you're also off there too. We have just as much free will as any other animal - which is to say none at all. Our free will is an illusion and if you look into neuroscience/ quantum physics/ cause and effect you will understand how this is so. Logically thinking? animals do that too - though they don't call it logic. We are not any different from animals (we are animals) at least we are no different in any of the way you've listed.

  57. onlinereikidojo

    It's interesting how 6 seconds occur before an act implying it was predetermined on the brain level. The implications are tremendous. Think about how often, though, a person changes their mind. The experiment doesn't elaborate. An interesting thing occurred to me while watching the video, I had the forethought that atheism biased the subject matter. The experiments are limited to the tools being used, yet imply something else is happening outside of the me, in union with the I. They have yet to discover a way to measure what isn't seen in that process.

  58. onlinereikidojo

    They came to the conclusion that the baby boy didn't have the sense of self in the mirror because he didn't demonstrate the proper actions, which I felt was possible, but considered he was able to separate the sense of me and was fully experiencing the sense of I (or oneness.)

  59. Jamie Megarity

    have the strange urge to munch on that brain lol

  60. Jamie Megarity

    Bang on there mate.
    was also thinking as well that perhaps domesticated dogs have a sense of self too. not all of them but some breeds. Border Collies for example. mine literally understands everything im saying to her. tell her to kiss my brother and she will go find him and give him a lick. plays the piano (hits it lol), plays dead when you shoot a finger gun at her. she even fetches the puppy when you tell her too.
    that is all training i suppose but she looks at herself in the mirror. if she notices a fluffed up bit of fur she will nibble at it.

    in short i think dogs are like us too inside

  61. jbriggs_87

    being human is weird

  62. Brian Swanson

    alcohol effects your brain. Your body is an instrument of your soul.

  63. mretchin

    I think that he (the filmmaker) made an error. The neuroscientist who shocked brains never said that the connectivity of neurons was directly the cause of consciousness. He only said that the two are related. To jump to a conclusion about consciousness from what he said is erroneous.

  64. Reyn Wing- Plaza

    gave only few contextual thought in
    the documentary

  65. Todd Morrow

    FYI - Jennifer Aniston does not appear in the film; only her picture.

  66. bumpercrop

    Exactly. Jennifer Anderson and self awareness? Aware of what?
    How she looks with or without plastic surgery? Perhaps the producer assumed that celebrity name recognition would attract
    a larger audience? Perhaps choosing a profession of people who rely on physical appearance for identity is the point? My prejudice turned me off, although premise is interesting.

  67. bumpercrop

    A person can be highly intelligent and unwise. A person can be wise and unintelligent. I recommend the 30 minute video on this site reviewing the philosopher, Montaigne. Our five senses supersede
    artificial stimuli, although false psychological stimulation does affect our mind. Advertising is a good example, via Pavlov's dog.

  68. bumpercrop

    you mean familiar things, like, disgust?

  69. bumpercrop

    Between the hammer of space and the anvil of mass, humans exist.
    -Thaddeus Golas

  70. JC

    OMG this answer is easy... It was once said "There is no such thing as finding oneselve only creating oneself." Bernard Shaw... Great Doc though... very informative regarding the biological... great questions...

  71. lulee

    Consciousness cannot be 'discovered', it can only be experienced. Humans are body AND spirit. Consciousness has to do with the spirit, which is why science will never have proof that it exists. He said he figured out a difficult problem when he was staring out the window, thinking of nothing. That's how it works- he let go of earthly, human thought and opened himself up to the source that is there for all of us.
    We all have the answers, but opening up and listening is the lesson we are all here to learn. Being restricted by what we can see and touch is like only reading the content page of a book.

  72. jaberwokky

    Very interesting doc. I'm not sure if I missed something in the 6 second delay experiment as I just kept thinking of video game reaction times and how divergent that is from what's presented here. Perhaps the nature of this particular test is, as stated somewhere in the comments below, dependant more on processing memories and hence the longer delay.

    I also wonder if those consciousness tests should be expanded to accommodate different levels. Surely all complex life requires some level of consciousness but to varying degrees and thus the tests should be adjusted accordingly?

  73. dier56

    Humans are not the only ones to have a sense of self. Study the great apes,elephants,

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