Speaker 1: Hi, this is David Eagleman. I've done a couple dozen
Speaker 1: of these podcast episodes so far, and I have been
Speaker 1: so gratified to see all the emails I get at
Speaker 1: podcasts at Eagleman dot com where people have comments or questions,
Speaker 1: and so what I want to do in this short
Speaker 1: episode today was just address a bunch of questions. Okay,
Speaker 1: Laura from Miami asks, is it true that we only
Speaker 1: use ten percent of our brain? Thank you for that question.
Speaker 1: It turns out that is not true. It turns out
Speaker 1: your brain is screaming with activity around the clock all
Speaker 1: the time. All the neurons in your brain are active.
Speaker 1: They're all popping off, even when you're asleep, even when
Speaker 1: you're in a deep sleep, they're popping off. So it
Speaker 1: turns out you do not use just ten percent of
Speaker 1: your brain. You use one hundred percent of your brain
Speaker 1: essentially all the time. Now, the question that's been interesting
Speaker 1: to me is why is it such a sticky myth
Speaker 1: even though it has no basis in the science. Why
Speaker 1: does it stick around? I think it's because it must
Speaker 1: be sort of aspirational or hopeful, which is, if we
Speaker 1: think we're all using ten percent of our brains and
Speaker 1: we think, wow, I could be much smarter than I
Speaker 1: am and do much more than I can do right now,
Speaker 1: But in fact it's a myth. Thank you for the question.
Speaker 1: I did an episode a little while ago about in
Speaker 1: groups and outgroups and the difference that we can measure
Speaker 1: in the brain, and Haroun from Berkeley wrote and asked,
Speaker 1: what if your brain shows a big difference between in
Speaker 1: and out groups, but you don't want that to be true,
Speaker 1: like with your behavior. So that's a great question, Harun.
Speaker 1: Just as a reminder, what we did in the study
Speaker 1: is we had people watch, let's say a hand get
Speaker 1: stabbed with a syringe needle. They see this piece of
Speaker 1: footage and it activates this pain network in the brain,
Speaker 1: and that is essentially a measure of empathy. But what
Speaker 1: we then did is we added a single word to
Speaker 1: each of the six hands. So we had Christian, Jewish, Muslim, Scientologist, Hindu, atheist.
Speaker 1: And now you see a hand get stabbed, and the
Speaker 1: question is which group do you belong to and do
Speaker 1: you have as much of an empathic response when you
Speaker 1: see any member of your outgroup gets stabbed? And generally,
Speaker 1: what we found is that you have a lower empathic
Speaker 1: response when the label is different when it's not your
Speaker 1: in group. So I think this is the heart of
Speaker 1: Harun's question is if you have that big difference in
Speaker 1: your empathic response, does it mean you're a bad person?
Speaker 1: Does it mean it has some reflection on how you're
Speaker 1: going to act? So let me say two things about this. First,
Speaker 1: it turns out that there is some amount of individual
Speaker 1: differences in this group outgroup difference. Everyone seems to have
Speaker 1: this reaction of caring more about their in group, but
Speaker 1: some show a bigger effect than others. But as far
Speaker 1: as we can tell, this does not map onto people's behavior.
Speaker 1: In other words, we can't help what our low level
Speaker 1: reactions are, what our first response is to something when
Speaker 1: we see something and there's a label. For example, whenever
Speaker 1: I see crunchy tortilla chips, my brain fires on all
Speaker 1: cylinders and tells me to grab those and stick them
Speaker 1: in my mouth so I can enjoy the crunch. But
Speaker 1: it doesn't mean that I actually do that. It doesn't
Speaker 1: mean I actually grab the chips. I have goals at
Speaker 1: different levels, like I've cut carbs out of my diet
Speaker 1: because I think that makes me healthier. And this is
Speaker 1: related to an even longer term issue that for reasons
Speaker 1: of vanity, I want to be an excellent shape and
Speaker 1: the chips would sabotage that. So despite this giant low
Speaker 1: level reaction from my brain when I see the chips,
Speaker 1: I have the capacity to override that decision with different
Speaker 1: layers of decision making. I am not slave to my
Speaker 1: first low level responses. And it's the same thing with
Speaker 1: these in group and outgroup responses. The effect that people show.
Speaker 1: That's the first low level thing that exposed how parts
Speaker 1: of their brain think. And it's massively important because it's
Speaker 1: different if there's no part of your brain that thinks
Speaker 1: that way at all. But when you have this first reaction,
Speaker 1: it has to be either implemented or overridden. In other words,
Speaker 1: if I didn't like chips at all, it would be
Speaker 1: a lot less effort to override that, and we wouldn't
Speaker 1: even be talking about this. So when it comes to
Speaker 1: a low level response of preferring your in group, no problem,
Speaker 1: that's just the first offer that your brain is making.
Speaker 1: But for most of us, we care about societal structure
Speaker 1: and fairness and equality, and so we override that. And
Speaker 1: in fact, I have a suspicion with no data to
Speaker 1: prove this. It's just a suspicion. But I think that
Speaker 1: perhaps some of the most socially conscious people, the people
Speaker 1: who fight against religionism or racism or whatever, that at
Speaker 1: least some of those people are battling some of their
Speaker 1: own quite powerful internal demons. And that's fine because in
Speaker 1: the final analysis, actions speak louder than words. Your behavior
Speaker 1: in the world is the only thing that counts. And
Speaker 1: I'll just mention one more thing. This is sort of
Speaker 1: a long answer, but something that's been discussed among the
Speaker 1: news outlets in the last several years is something called
Speaker 1: the implicit association's test, and there's a whole flurry of
Speaker 1: papers about this, and that is, you see things on
Speaker 1: the screen and you have to react by hitting a button,
Speaker 1: whether it's a good or a bad thing. So maybe
Speaker 1: it's a particular religion or a particular race, or a
Speaker 1: particular sexual orientation or whatever. And the question is, is
Speaker 1: your reaction time a little bit slowed down when you're
Speaker 1: seeing some other group and could that mean that you
Speaker 1: implicitly have some sort of negative association with that group. Now,
Speaker 1: the question in the media has been could this someday
Speaker 1: be used in a courtroom. If let's say an employer
Speaker 1: fires somebody, could you use the implicit associations test to demonstrate, Hey,
Speaker 1: we think this guy is a racist and that's why
Speaker 1: he did the firing. From a neuroscience point of view,
Speaker 1: I think it would be ridiculous to allow that into
Speaker 1: a courtroom because someone might have a racist or sexist
Speaker 1: or religious response at an unconscious low level in their brain,
Speaker 1: and that tells you nothing about how they're going to
Speaker 1: act in the world, or whether the firing of that
Speaker 1: employee had anything to do with that low level brain response.
Speaker 1: As I said, many people actually act better in the
Speaker 1: world because they're embarrassed by their internal first reaction. It
Speaker 1: would be like taking me to court and concluding I
Speaker 1: must be the one who stole the bag of chips
Speaker 1: because I have the biggest neural response to the site
Speaker 1: of chips. It doesn't tell you anything about my final behavior,
Speaker 1: my final decision in a situation. The only thing that
Speaker 1: can give you a good indication of someone's behavior is
Speaker 1: their prior behavior, not their brain's knee jerk response. Thanks
Speaker 1: for that question, okay. Jordan from LA asked a question
Speaker 1: from my episode about dreams. One of the things I
Speaker 1: was talking about there is when somebody goes blind, their
Speaker 1: visual cortex gets taken over by other neighboring territories. And
Speaker 1: so my hypothesis is that the reason we dream, it's
Speaker 1: like a screen saver that protects the visual cortex from
Speaker 1: takeover during the nighttime. So Jordan's question is, what about
Speaker 1: people who go blind later in life. Well, there's actually
Speaker 1: a lot of data on this sort of thing. People
Speaker 1: who become blind after the age of seven have more
Speaker 1: visual content in their dreams than those who become blind earlier,
Speaker 1: and that is consistent with the fact that the occipital
Speaker 1: lobe this part back here your visual cortex. In people
Speaker 1: who become blind later, that gets less fully taken over
Speaker 1: by the other senses, and so the activity that you
Speaker 1: have is experienced more visually. In other words, if you
Speaker 1: go blind later, your visual cortex is more intact and
Speaker 1: less likely to get taken over, and so you have
Speaker 1: more visual dreams. Okay, this next question is from Sampridi
Speaker 1: in Boston. Why are we so bad at remembering what
Speaker 1: happened during a dream? Okay, Well, this is because during
Speaker 1: dreaming you've got these other brain areas like the hippocampus
Speaker 1: and the prefrontal cortex that are essentially shut down. They
Speaker 1: are less active during dream sleep than they are during
Speaker 1: the waking state, and presumably this is what accounts for
Speaker 1: our difficulty remembering our dreams. Now, why does your brain
Speaker 1: shut down these areas so that dreams don't get remembered.
Speaker 1: One possibility is that there's no need to write down
Speaker 1: memory if the central purpose of dream sleep is just
Speaker 1: to keep the visual cortex actively fighting off its neighbors.
Speaker 1: And this is why when you wake up, you say,
Speaker 1: oh my gosh, I just experienced this wild dream, and
Speaker 1: you tell it somebody. You try to do it, but
Speaker 1: it's like gossamer, it just goes away and you can't
Speaker 1: remember what the dream was after just fifteen minutes. And
Speaker 1: by the way, I think this is similar to what
Speaker 1: it is like to have Alzheimer's disease, where you say, okay,
Speaker 1: i'll be there in five minutes, I'll meet you downstairs,
Speaker 1: and then it just sort of goes away and you
Speaker 1: can't remember it. I think, in a sense, we all
Speaker 1: know what it is like to be a person with
Speaker 1: Alzheimer's because we have that every morning when we wake
Speaker 1: up and one possibility about why memory does not get
Speaker 1: written down during dream sleep is just because there's actually
Speaker 1: no need to write down memory. It's not supposed to
Speaker 1: be cataloged for the future. If really the purpose of
Speaker 1: dream sleep is just to keep the visual cortex defended
Speaker 1: against takeover at nighttime, keep sending in your questions to
Speaker 1: podcasts at eagleman dot com and listen to the full
Speaker 1: episodes of Inner Cosmos wherever you listen to your podcasts,
Speaker 1: and also on YouTube, where you can leave questions or comments.
Speaker 1: Until next time. I'm David Eagleman, and this is the
Speaker 1: Inner Cosmos inbox.