 Every time I eat Italian food, I can't help but wonder if it's why humans evolved brains in the first place. I mean, penning for your thoughts? If all the previous videos concerning human thought haven't been enough to convince you, reason is kind of a big deal for me. I regularly think about stuff like the Apollo missions or the Principia, towering achievements wrought by human brains, science, the glorious future of humankind! So believe me that this wasn't an easy script for me to write. It's possible that the higher-level human reasoning that's responsible for mathematics and rocket engines might be a mistake. No, no, no, no! I don't mean that it's a bad thing. Not that crazy. But maybe it's more of a happy accident than a deliberate development. At least according to a relatively new theory. A quick definition. The sort of reason that I'm talking about is the high-level, rules-based, logical processing that we use for things like solving crossword puzzles or figuring out our gas mileage. It's a relatively recent evolutionary development and humans sort of pride ourselves on it. I mean, homo sapiens sapiens, am I right? Reason allows us to predict and shape the future, which is a pretty awesome evolutionary advantage. So you might expect that we evolved it for that purpose. But there's a bit of a problem with this idea. We actually kind of suck at reasoning. Wikipedia has a list of over 100 cognitive biases. Those are built-in problems with human thought that prevent us from believing rational things, ranging from consistent overestimation of certainty, to drawing different conclusions from the same data arranged in different ways. Perhaps chief among these problems, there's a huge constellation of biased thought processes collectively called confirmation bias. Basically, once people have an idea in their heads, it's very difficult to dislodge it, even with convincing evidence to the contrary. Humans have an irresistible and universal intuition to rate new information which supports our pre-existing ideas as being more important than information which might refute them. If we were thinking rationally, we'd weigh all information equally, but our brains simply don't work that way. So if humans evolved reason to guide individuals toward truth, we got a somewhat broken and crappy version of it. Given we've managed to discover a lot of really amazing stuff with what we got, but we did so in spite of these weird anomalies. But what if that's not why we evolved it? In 2011, Hugo Mercier and Dan Sperber published a paper entitled, Why Do Humans Reason? Arguments for an Argumentative Theory, where they suggested that maybe the reason that reason first developed was to convince other people that were right. In other words, to argue. Now, if you've had experiences with crappy evolutionary psychology, your first response is probably, okay, so what? It's really easy to come up with untestable cockamamie ideas about why people think the way that they do. But this argumentative theory has some very interesting implications that square with a whole bunch of observations about human psychology. The main premise is that communication is a great tool for survival, so long as you can be sure that what you're being told is true. If there's a discrepancy between what you're telling somebody and what they already believe, you need some sort of way to verify that the informational content of your message is worth changing their mind for. A good way to do that is to present that information in a way that shows that it's largely in line with how they already view the world, so that it's probably less effort for them to change their mind about this one little thing than it is to ignore your message. In other words, to form a convincing argument. In that context, a lot of these supposed anomalies that conflict with rational decision-making start to make some sense. For example, there's some compelling evidence that shows that people are generally pretty lazy when it comes to justifying their own ideas when left to their own devices. Why are you voting for this guy? I don't know, he seems nice. However, if you tell somebody that they have to convince some other jerk who believes something different, suddenly their brains kick into high gear and turn out very logical and well-thought-out justification for their beliefs. That's called motivated thinking, and it's puzzling that it only really happens when somebody feels like they have to argue, unless that's what reason developed for in the first place. Confirmation bias also makes a whole lot of sense in an argumentative context, because if you're just trying to convince somebody that you're right, you'd probably show a cognitive preference for evidence that supports your idea and ignore or even refute evidence that might undermine it. That's a little bit depressing. You might wonder how we even got to this point of developing rationality as a mechanism for truth instead of just sitting around and convincing each other of whatever. But there is a bright side to this more social hypothesized origin for reason. The truth tends to win in groups. Individuals tend to be terrible at figuring out the truth on their own because of all of these cognitive biases, but put those same individuals into a group where they can discuss things in this fashion, where multiple parties are proposing new ideas, generating rational support to argue for them, critiquing opposing ideas and evaluating who sounds like they're making the most sense. Research shows that collectively, they are way better at figuring out the answers to some very hard questions. Like, there's this logic puzzle called the Waste and Selection Task, which even the brightest individuals only get right around 10 to 20% of the time. But put those individuals into a group and let them argue, that jumps to 80%. That's crazy! Individually, we have this whole laundry list of problems that we have to either avoid or compensate for so that we don't trip ourselves up. But given a difficult problem to discuss together, at least in some cases, we actually do pretty well. Anyways, we really don't have any way to directly test the evolutionary conditions that led to us developing rationality, so all of this could be nonsense. Reason remains a very useful tool with some very severe issues. As such, regardless of your opinion about where reason came from, it makes sense to learn about those issues and compensate for them wherever possible. After all, we don't just want to win arguments, we also want to be right. And win arguments. Do you think that the argumentative theory of human reason is plausible? Please leave a comment below and let me know what you think. Thank you very much for watching. Don't forget to blah blah subscribe, blah share, and don't stop thunking.