So one of the ways that people realize that this was really important and have studied this is by looking how children develop the ability to use social cues. So very simple games have been used with children where an adult will gaze of one or two locations, and the child's trying to find a toy. And at about 14 months of age, children begin to be able to use gaze direction or the angle that you're looking to guess where a toy might be hidden. At the same time, they also start to use gestures, like this pointing gesture, for the same purpose. They can understand you are trying to tell them where something is in the environment, and they start to understand that you may have seen something that they hadn't seen before. And using social cues is an indicator that they are doing this very interesting calculation about what others are thinking. The reason this is so important, of course, is because we think that the ability to think about the thoughts of others is what allows for humans to imitate one another. It's what allows humans to intentionally deceive one another, it also allows us to have empathy for one another, to actually feel the feelings of someone else, and it's also crucial for collaboration. And of course, everything that's human follows from these abilities, whether it's culture, language, politics, or institutions. Without imitation, deception, empathy, collaboration, which totally relies on Theory of Mind, you couldn't have all the things that we think of as being human. So people think it's kind of a big deal whether or not Theory of Mind is really unique to our species. We know that it develops, and we know how it develops, but is it really just something about our species or not? So to answer that question, we took a phylogenetic approach. We looked at our close relatives, and we did the same types of games that other researchers have done with children. And we simply hid something in one of two locations, and then we just try to tell the animal, in this case Fifi the chimpanzee, we try to tell Fifi where the grape is. You can see on the middle of the table there, there's a little red object, that's a grape. It's a big deal to Fifi just like the peanuts were to Yoyo, and she wants to find them. We're gonna hide that in one of two locations, and then I'm just gonna tell her where it is. And the question is, can she find it? So I'm hiding it in one of two places. It's in the cup on the left. And now, I'm going to use that block to tell her it's over there, and you see, she, oops, makes the wrong choice. Oh, scratches her head. Not happy. All right, so you might not know that that block the first time you see it is a cue, or a social cue or a gesture, trying to help you find something. But if I did that repeatedly, two or three or ten times, you would very quickly realize that I'm trying to communicate with you. That my intention is to help you, my goal is to help you find the food. But, the amazing thing was, when we played these types of cooperative communicative games with our close relatives, chimpanzees and even bonobos, they do not solve these problems without lots and lots and lots and lots of practice. I spent weeks of my life trying to tell chimpanzees and bonobos where hidden food is, using lots of different gestures and social cues, and it's really hard. Once they finally learn to use one, if you switch to a new gesture, something like this block that they've never seen before, they completely fall back to chance, and they choose 50/50. They're just guessing, they don't know that I'm trying to help them. And so one of the interpretations of this is that really humans and human infants have a unique and special ability that evolved during our species evolution that allows us to solve all sorts of problems. When we directly compared the development of a set of infant chimpanzees and in a set of infant bonobos on a wide range of cognitive games, what we found was that while chimpanzees and bonobos develop in a very similar way when it comes to solving physical problems, using tools, remembering where things were hidden, all three species look really the same. But when you look at social problems like the ones I just showed you where you hide food and try to communicate where it is, that's where human infants really develop extremely quickly relative to other apes in our family. So that's what got people excited about the idea that Theory of Mind really is something different about our species, and it may even be completely unique. So Theory of Mind, to wrap up, Darwin recognized that human cognition was a major challenge for evolutionary theory. The ecological approach suggests that social problems drove the evolution of both primate and human cognition. Theory of Mind allows for flexible prediction of behavior by assessing the perceptions, intentions, and knowledge of others. Humans have early emerging social cognition and understanding of communicative intentions when compared to other apes, and that may be what makes us unique. And so then overall, that's why Theory of Mind has been thought of to be so important. But that's going to lead us to some interesting discoveries about our best friend and open the door to finding out why dogs are so remarkable.
