WEBVTT 00:00:00.017 --> 00:00:07.737 Tony, any other problems before we start? This is the Convergent Science Network podcast. 00:00:09.757 --> 00:00:14.257 Leading researchers in the domain of neuroscience, brain theory and technology 00:00:14.257 --> 00:00:17.977 are interviewed by Paul Vesure and Tony Prescott. 00:00:21.997 --> 00:00:26.297 It's Paul Vesure at Convergent Science Network podcast, together with my colleague 00:00:26.297 --> 00:00:30.697 Tony Prescott, co-chairing the BCBT Summer School. 00:00:31.237 --> 00:00:37.337 And today we're with Dorothy Fregese, who was our speaker, and Dorothy, 00:00:37.437 --> 00:00:42.237 who has a cough, so we will just ignore those sounds. 00:00:43.497 --> 00:00:50.357 So Dorothy, your talk focused on your work on tool use in monkeys, right? 00:00:50.817 --> 00:00:54.897 So why tool use in monkeys? What makes it interesting? 00:00:56.097 --> 00:01:02.297 Well, tool use in primates as a whole is interesting from an anthropocentric 00:01:02.297 --> 00:01:09.537 perspective, because humans are the quintessential tool users. 00:01:09.877 --> 00:01:14.157 We have shown tool use from the dawn of our species. 00:01:15.057 --> 00:01:21.617 It's something that we know is culturally important and is important in the success of our species. 00:01:22.037 --> 00:01:26.177 It's something that children show spontaneously from very early in life. 00:01:26.337 --> 00:01:29.877 It's a very essential component of being human. 00:01:30.077 --> 00:01:35.837 So when we see tool use in another species, we automatically are curious about 00:01:35.837 --> 00:01:41.837 whether they are using tools in the same way we are, if they are organizing 00:01:41.837 --> 00:01:43.537 that activity in the same way. 00:01:44.117 --> 00:01:46.377 So that's the anthropocentric perspective. 00:01:46.797 --> 00:01:49.737 And of course, there are other reasons to be interested in it. 00:01:49.757 --> 00:01:53.217 You might be interested in it solely from the point of view of the biology of 00:01:53.217 --> 00:01:57.937 the animals themselves to understand what this behavior contributes to their way of life. 00:01:58.517 --> 00:02:04.717 And you might also be interested in it from the point of view of understanding the... 00:02:06.475 --> 00:02:10.775 The neural substrates or the anatomical substrates that go along with the forms 00:02:10.775 --> 00:02:12.675 of tool use that are interesting to humans. 00:02:12.855 --> 00:02:17.455 So in non-human primates, that means being interested in the use of the forelimbs 00:02:17.455 --> 00:02:18.715 and especially the hands. 00:02:19.555 --> 00:02:24.615 And we see tool use in that form in non-human primates that they're using tools with their hands. 00:02:24.675 --> 00:02:27.995 So we're interested in how that whole system is coordinated. 00:02:28.355 --> 00:02:34.015 Okay, so then you have tool use. How now do we define tool and how do we define use? 00:02:34.755 --> 00:02:40.835 So what makes a tool? This is a very good question, and there is no clear consensus 00:02:40.835 --> 00:02:43.475 in the animal behavior community about this. 00:02:43.755 --> 00:02:50.455 We recognize a tool after it has been used, and it is a tool because it has been used. 00:02:50.655 --> 00:02:56.115 So almost anything can be a tool for some purpose. It isn't necessarily something. 00:02:56.295 --> 00:02:59.475 It's not an intrinsic quality of the object itself. 00:03:00.035 --> 00:03:04.155 It's imposed upon it by the actor who uses it for something. 00:03:04.155 --> 00:03:08.775 So, for instance, I have a little box here of cardboard, and I can use this, 00:03:08.815 --> 00:03:13.555 if I wanted to, to knock over my cup of tea. I'm not going to do that. 00:03:13.815 --> 00:03:18.995 But then if I did, I would be using this box, cardboard box, as a tool. 00:03:19.135 --> 00:03:22.955 Well, when it's sitting here on the table without my doing anything with it, 00:03:22.995 --> 00:03:26.455 nobody would say that that was a tool to knock over a cup. I could use Tony's 00:03:26.455 --> 00:03:28.595 laptop to wipe away the tea. 00:03:28.755 --> 00:03:31.735 Yes, you could. Right, exactly. He wouldn't like that. But then, 00:03:31.735 --> 00:03:34.475 so the point you made there, which I think was really important, 00:03:34.675 --> 00:03:40.055 is to realize that actually there's not a real theory at this point in time of tool use. 00:03:40.315 --> 00:03:44.935 No, there's not. There's a lot of theories about why individuals should use 00:03:44.935 --> 00:03:49.935 tools and some ideas about what kinds of individuals are able to do this, 00:03:50.015 --> 00:03:53.915 but there's no single theory, there is no theory of tool use. 00:03:55.655 --> 00:04:01.355 Is there a reason to think that tool use is evidence of a certain kind of cognition? 00:04:01.695 --> 00:04:03.695 Is that a particular reason to focus on it? 00:04:05.375 --> 00:04:10.895 In the animal behavior community, I would say no, because we see tool use defined. 00:04:11.155 --> 00:04:14.095 You asked me about the definition, so I'll come back to that now. 00:04:14.655 --> 00:04:20.595 What exactly is tool use? So, as we have no theory of tool use, 00:04:20.695 --> 00:04:29.395 tool use is defined descriptively as the phenomenon wherein an individual uses 00:04:29.395 --> 00:04:33.115 an object to produce a spatial or force relation, 00:04:33.355 --> 00:04:38.175 a manipulatable object, so it has to be an unattached object that the actor 00:04:38.175 --> 00:04:44.535 controls and moves and uses to produce a change in another object or a surface. 00:04:45.275 --> 00:04:48.295 So for instance, I can use a shovel to dig a hole. 00:04:48.495 --> 00:04:53.415 I can use a probe to put into a small opening to push something out. 00:04:53.555 --> 00:04:58.315 All those are examples of tool use. But there are many gray areas if you have 00:04:58.315 --> 00:05:00.135 as broad a definition as that. 00:05:00.315 --> 00:05:06.575 And so this is a point of continuing discussion in the animal behavior community. 00:05:06.575 --> 00:05:10.355 In the linguistic community and in the philosophical community, 00:05:10.595 --> 00:05:14.415 there are other treatments of what constitutes a tool. 00:05:14.635 --> 00:05:19.695 I think Hediger has talked about what constitutes a tool. 00:05:19.775 --> 00:05:26.255 He talks about ready-to-hand and other things that some people have discussed in terms of using tools. 00:05:26.255 --> 00:05:31.875 But the animal behavior community mostly doesn't worry about the philosophical definitions, 00:05:31.975 --> 00:05:37.675 and they're more concerned with the very functional definition of controlling 00:05:37.675 --> 00:05:43.215 an object and moving it in space to achieve an outcome on a distal target, 00:05:43.355 --> 00:05:45.115 or sometimes even on the body itself. 00:05:45.115 --> 00:05:48.935 Well, it's interesting also given Tony's question that actually your definition 00:05:48.935 --> 00:05:51.775 is really emphasizing the pragmatics of tool use, right? 00:05:51.795 --> 00:05:59.315 You gave four criteria of, let's say, a functional extension to act upon an 00:05:59.315 --> 00:06:03.335 object, detainment of goals, and that there's a force relationship. 00:06:04.075 --> 00:06:09.315 So why do you highlight these four properties of tool use? 00:06:09.635 --> 00:06:12.675 Why do I highlight those? Yeah, but why do you emphasize those and why do you 00:06:12.675 --> 00:06:16.655 leave out this reasoning component that also Tony was sort of asking about? 00:06:16.755 --> 00:06:18.135 Because I study behavior. 00:06:18.375 --> 00:06:25.375 I want it to be observable. So those are aspects that I can measure directly or observe directly. 00:06:25.815 --> 00:06:27.755 And I can't observe reasoning directly. 00:06:28.515 --> 00:06:32.155 So if you would include, let's say, a neurophysiological component that might 00:06:32.155 --> 00:06:35.695 give you a correlate of reasoning, then you would be happy to entertain it. 00:06:36.813 --> 00:06:43.013 I'm not ruling it out, but for me, to see, for example, if I had functional 00:06:43.013 --> 00:06:49.533 fMRIs running the whole time I was watching an individual use an object as a tool, 00:06:49.713 --> 00:06:54.513 I might be able to say something about the neural activation that accompanies 00:06:54.513 --> 00:06:58.893 tool use, but I'm not sure I would be able to say which aspect of that image 00:06:58.893 --> 00:07:01.313 I'm looking at constitutes reasoning. Mm-hmm. 00:07:02.053 --> 00:07:07.953 Okay. But is this where the animal behavior community takes a different perspective than, 00:07:08.033 --> 00:07:14.113 say, the people in human anthropology who are looking at hominid tool use as 00:07:14.113 --> 00:07:18.093 evidence of a progression towards later forms of human cognition? 00:07:18.373 --> 00:07:25.313 Well, there are people in anthropology who are sort of bridging anthropology and neuroscience. 00:07:25.593 --> 00:07:31.993 I'm thinking, for example, of Dietrich Stout, who does neuroimaging of humans 00:07:31.993 --> 00:07:34.813 as they are napping stone, for example. 00:07:37.793 --> 00:07:42.873 So, I'm sorry, what was the question again? Well, is there a difference in perspective 00:07:42.873 --> 00:07:45.993 perhaps between that community and the animal behavior community? 00:07:46.213 --> 00:07:53.333 Oh yes, yeah, there is. Because an archaeologist or an anthropologist is approaching 00:07:53.333 --> 00:07:55.393 it from a specifically anthropocentric perspective, 00:07:55.833 --> 00:07:58.873 their interest is in explaining the origins 00:07:58.873 --> 00:08:04.793 of human behavior and in examining the similarities between behavior of non-human 00:08:04.793 --> 00:08:10.973 primates and human primates in an effort to help understand the fossil record 00:08:10.973 --> 00:08:17.933 or the archaeological record of extinct hominids and early human ancestors. 00:08:18.353 --> 00:08:22.793 So they have a vested interest in trying to understand what features of tool 00:08:22.793 --> 00:08:27.973 use might correspond to what sorts of evidence they find about early forms of 00:08:27.973 --> 00:08:31.853 tool use in our ancestors. 00:08:32.093 --> 00:08:37.333 They look, for example, at transport and selection of materials and things that 00:08:37.333 --> 00:08:40.233 are evident in the archaeological record. 00:08:40.493 --> 00:08:43.633 We can look at those things in behavior of extant primates as well, 00:08:43.713 --> 00:08:47.373 and there's a community of people that are doing that. Susana Carvalho is an 00:08:47.373 --> 00:08:51.533 example of a person who does that, and Michael Haslam, and there are others. 00:08:52.213 --> 00:08:56.333 You are bringing to your study some theoretical frameworks, but you're suggesting 00:08:56.333 --> 00:08:58.453 that those would be different ones. Yes. 00:08:58.753 --> 00:09:00.633 Well, my own work is…. 00:09:02.452 --> 00:09:10.072 I would say, inspired by, not so tightly constrained by, but inspired by a couple 00:09:10.072 --> 00:09:15.412 of different streams of reasoning coming out of psychology and movement science out of psychology. 00:09:16.812 --> 00:09:21.992 I've been inspired by the work of the Gibsons, J.J. 00:09:22.012 --> 00:09:28.612 And Eleanor Gibson, who jointly contributed greatly to the formation of a school 00:09:28.612 --> 00:09:30.832 of psychology known as ecological psychology. 00:09:30.832 --> 00:09:37.572 Psychology, and they were both extremely active in the middle and later part of the 20th century, 00:09:38.252 --> 00:09:44.072 and by the work of Nikolai Bernstein, who was a Russian physiologist, 00:09:44.192 --> 00:09:45.252 movement physiologist, 00:09:45.492 --> 00:09:50.392 whose professional career was actually in the first half of the 20th century, 00:09:50.552 --> 00:09:56.072 but whose work was translated into English in the 1960s and became very influential 00:09:56.072 --> 00:09:59.512 in the English-speaking community after that time. 00:10:00.492 --> 00:10:09.152 And so the Gibsons emphasized the role of the individual in actively seeking information, 00:10:09.472 --> 00:10:16.252 using the senses to gain information and the role of perceptual learning in 00:10:16.252 --> 00:10:17.212 the development of skill. 00:10:17.512 --> 00:10:24.592 And they emphasized that the information that an individual needs to perform 00:10:24.592 --> 00:10:27.492 tasks is in the environment. 00:10:27.652 --> 00:10:33.152 It's the individual's task to discover that information and to learn to make 00:10:33.152 --> 00:10:36.852 use of it, but not to somehow construct the information. 00:10:38.612 --> 00:10:44.072 And Bernstein's interest was in motor skills in particular, and so this is where 00:10:44.072 --> 00:10:48.832 it dovetails for me with an ecological perspective. 00:10:49.212 --> 00:10:57.652 So Bernstein was very interested in how humans with multi-joint limbs and many 00:10:57.652 --> 00:10:59.432 degrees of freedom of movement, 00:10:59.632 --> 00:11:06.032 how a system composed of many degrees of freedom could be a. 00:11:07.503 --> 00:11:12.583 Could be organized to achieve a specific goal and to achieve that goal effectively 00:11:12.583 --> 00:11:18.703 and with minimal effort, even when circumstances vary. 00:11:19.003 --> 00:11:22.963 So, for instance, if you are swinging a baseball bat and someone is pitching 00:11:22.963 --> 00:11:25.183 the ball to you and your goal is to hit the ball, 00:11:25.323 --> 00:11:28.863 sometimes the ball is a little faster, sometimes it's a little slower, 00:11:28.923 --> 00:11:31.863 sometimes you have a bat that weighs a little more or a little less, 00:11:31.863 --> 00:11:34.943 Sometimes the pitch is a little inside or a little outside, 00:11:35.083 --> 00:11:42.463 and a skilled batter can handle all of that, whereas a novice perhaps could handle one speed, 00:11:42.723 --> 00:11:45.723 one bat, one position, but not handle the variability. 00:11:45.723 --> 00:11:50.623 And Bernstein was very interested in how one assembled from all the multiple 00:11:50.623 --> 00:11:52.143 degrees of freedom in the joints 00:11:52.143 --> 00:11:57.043 and all the variation in the physical position of the body and so forth, 00:11:57.103 --> 00:12:03.343 how one could arrive at effective action even in the face of all these variations. 00:12:04.463 --> 00:12:11.423 So then you focus on non-human primates and in particular capuchin monkeys, right? 00:12:12.723 --> 00:12:17.763 So but now you were telling us that right now among the experts who count the 00:12:17.763 --> 00:12:23.323 number of non-human primates that are around, there are about 500 species of 00:12:23.323 --> 00:12:24.343 non-human primates. More than. 00:12:24.583 --> 00:12:28.643 More than? Yeah. Okay, so what? The number changes, but it's somewhere around 560. 00:12:28.783 --> 00:12:32.463 Okay. But it may be a little more by now. New species discovered all the time. 00:12:32.463 --> 00:12:34.923 Okay, but it's of that order, yeah? 00:12:35.903 --> 00:12:42.443 And so now of all these species we know, how many are really known to use tools 00:12:42.443 --> 00:12:44.903 in a way that would be, let's say, accepted? 00:12:46.563 --> 00:12:52.383 So among the old world monkeys, the Burmese macaques, Macaca fascicularis, 00:12:52.483 --> 00:12:56.543 and then there's a subspecies name that indicates the Burmese version. 00:12:56.623 --> 00:13:03.483 I think it's Aurea, but I'm not exactly certain of the subspecies designation. And the orangutan? 00:13:04.433 --> 00:13:11.853 And the common chimpanzee. And the bearded capuchin uses tools routinely and habitually. 00:13:12.033 --> 00:13:16.913 And there are some other capuchins in the same genus as the bearded capuchins, 00:13:16.993 --> 00:13:22.213 which is now recognized as belonging to the genus Sapajou, which is a sister genus to Cebus. 00:13:22.413 --> 00:13:26.893 It has historically, for a long time, been in the genus Cebus, 00:13:26.993 --> 00:13:30.173 and in 2012 split into Sapajou. 00:13:30.253 --> 00:13:35.513 So this is very recent. And there are two other species of Sipaju that have 00:13:35.513 --> 00:13:41.913 been observed to use tools in nature, and they are both in adjacent areas to 00:13:41.913 --> 00:13:44.833 where the libidinosis is, the bearded capuchin. 00:13:45.933 --> 00:13:49.533 Okay, so there's two things then. That means of these 500 plus, 00:13:49.833 --> 00:13:51.613 or let's say 600 if you round it up, 00:13:51.973 --> 00:13:57.273 species of non-human primates, there's a handful, let's say 1%, 00:13:57.273 --> 00:14:01.693 that are known to routinely use tools? In the wild. 00:14:01.973 --> 00:14:07.453 In the wild. Yeah. And of those, those six, they appear to be rather strongly, 00:14:07.533 --> 00:14:12.893 more genetically related to each other than to the rest of these species or not? 00:14:12.993 --> 00:14:18.813 Or there's no… Well, the New World monkeys, the capuchins, are very remotely 00:14:18.813 --> 00:14:21.053 related to the Old World primates. 00:14:21.093 --> 00:14:27.633 The split was somewhere around 35 million years ago. ago, and then so the split 00:14:27.633 --> 00:14:31.793 between the New World and the Old World simian primates was about at that time. 00:14:32.353 --> 00:14:37.233 And the split among the other apes, the chimpanzees, the orangutans, 00:14:37.313 --> 00:14:40.733 and the humans is much more recent than that, perhaps 10 million years or less. 00:14:40.993 --> 00:14:47.913 So there's a big temporal gap in the most recent shared ancestor between the 00:14:47.913 --> 00:14:51.173 New World monkeys and the Old World monkeys. So the important conclusion being 00:14:51.173 --> 00:14:55.413 that- This is probably independently- Exactly, right. Evolved, yeah. 00:14:57.853 --> 00:15:02.473 Okay, so independently evolved, but also independent of, let's say, 00:15:02.673 --> 00:15:07.653 or it's less likely to strongly depend on a genetic program, 00:15:07.933 --> 00:15:10.253 on genetic pre-specification, right? 00:15:10.333 --> 00:15:16.573 Well, it would be impossible for me to specify what sort of genetic program 00:15:16.573 --> 00:15:22.133 could result in the suite of attributes that I think support tool use. Yeah. 00:15:22.213 --> 00:15:25.613 They're very diffuse and they're related more to foraging style. 00:15:26.013 --> 00:15:31.953 It's not a specific action or a specific problem that they use tools to solve. 00:15:31.973 --> 00:15:36.973 It's something about these species' approach to what they can do with objects. 00:15:37.373 --> 00:15:39.453 So if it's convergent…, 00:15:40.866 --> 00:15:44.506 Are we looking at a set of features that are converging? 00:15:44.926 --> 00:15:51.506 So, for instance, are there anatomical features that appear to be convergent? I would say no. 00:15:54.366 --> 00:15:59.726 The forms of tool use that non-human primates perform involve using their hands 00:15:59.726 --> 00:16:05.426 to hold an object, but it's usually holding the object in a relatively common 00:16:05.426 --> 00:16:08.726 way, in what we would call a power grip. 00:16:08.726 --> 00:16:15.526 Grip, they're not necessarily using very fine precision to manipulate very small objects. 00:16:15.706 --> 00:16:17.506 They're not sewing, for example. 00:16:17.846 --> 00:16:21.906 So a power grip would be using all your fingers? Yeah, in a convergent grip. 00:16:22.006 --> 00:16:23.326 Right. And that's sufficient. 00:16:23.606 --> 00:16:27.366 That's all you need. If what you want to use is a stick to probe into a hole, 00:16:27.486 --> 00:16:30.146 you don't need a precision grip. You can use a power grip, and they do. 00:16:30.346 --> 00:16:37.366 Mm-hmm. So it isn't a point of differential dexterity. 00:16:38.066 --> 00:16:44.126 Right. But it is, if you look what is common across these species, 00:16:44.406 --> 00:16:50.506 it's not unique to them, but it is common to them that they are extractive foragers. 00:16:50.826 --> 00:16:58.466 And so from an ecological perspective, an individual that is finding food in 00:16:58.466 --> 00:17:04.506 hidden locations and has to work to open up a substrate and get at what's inside, 00:17:04.506 --> 00:17:10.926 That individual is oriented towards the possibilities of objects that it can't see. 00:17:11.146 --> 00:17:14.766 You have to find something behind an exterior. 00:17:15.106 --> 00:17:19.786 So you are interested in destroying objects and getting at things. 00:17:19.786 --> 00:17:26.846 And this way of life promotes an interest in, I would say, acting roughly with 00:17:26.846 --> 00:17:31.726 objects, with breaking them, with banging them, with moving them around, 00:17:31.926 --> 00:17:34.206 with being proactive towards objects. 00:17:34.506 --> 00:17:38.966 There's a lot of handling involved. And these species all do that. 00:17:39.830 --> 00:17:43.930 So, but we have a precision grip where we can use our opposable thumb. 00:17:44.070 --> 00:17:45.350 Humans do, yes. Precisely gripped. 00:17:45.650 --> 00:17:52.130 Now, how common is that in the rest of the non-human primates? 00:17:52.150 --> 00:17:57.950 So the precision grip in the human form where the thumb rotates to face the 00:17:57.950 --> 00:18:03.190 other digits and you have a perfect opposition possible between the tip of the 00:18:03.190 --> 00:18:05.050 index finger and the thumb, 00:18:05.050 --> 00:18:08.550 old-world primates can do that. 00:18:09.450 --> 00:18:12.710 So that includes old-world monkeys and it includes apes and humans. 00:18:14.210 --> 00:18:19.650 Humans, the morphology of the human hand is a little bit different. 00:18:19.690 --> 00:18:22.630 Each species' hand is a little bit different from the next species. 00:18:23.010 --> 00:18:27.590 So we achieve this grip in a human way and other species accomplish it in a 00:18:27.590 --> 00:18:28.750 slightly different way. 00:18:28.810 --> 00:18:33.730 For example, the thumb of apes is much smaller than the thumb of humans, 00:18:33.850 --> 00:18:38.030 so they have to bend the index finger farther to touch the thumb, for example. 00:18:38.210 --> 00:18:42.490 But they still achieve a perfectly useful precision grip, despite the fact that 00:18:42.490 --> 00:18:44.350 their thumb is much shorter than ours. 00:18:45.070 --> 00:18:49.690 All old world monkeys have the joint morphology to achieve that kind of movement 00:18:49.690 --> 00:18:52.230 of the thumb and opposition of the of the fingers. 00:18:53.230 --> 00:18:59.110 New world monkeys, as far as we know, only one group of new world monkeys can 00:18:59.110 --> 00:19:01.270 achieve that kind of a precision and grip, 00:19:01.530 --> 00:19:05.790 but we actually haven't explored very much among all the species, 00:19:05.910 --> 00:19:09.450 so I don't want to claim that no other New World monkey does this, 00:19:09.550 --> 00:19:13.590 but I can say that so far we know that capuchins can do it, and that's both 00:19:13.590 --> 00:19:15.150 genera, cebus and sapaju, 00:19:15.350 --> 00:19:18.390 and we don't know very well about other species. 00:19:18.630 --> 00:19:24.150 But capuchins, in any case, can achieve a functional opposition, 00:19:24.290 --> 00:19:30.330 and they place the side of the thumb against the side or the pulp of the index finger. 00:19:30.850 --> 00:19:35.990 And it works functionally. It's not as strong a precision grip as humans achieve, but it works. 00:19:36.210 --> 00:19:39.110 You can pick up small objects in that way. 00:19:40.209 --> 00:19:43.949 But that would be then the only species known to do that. New world monkeys. 00:19:44.109 --> 00:19:45.309 Exactly. Yeah. All right. 00:19:46.389 --> 00:19:53.029 But in terms of the kinds of tool use that you see among non-human primates, 00:19:53.109 --> 00:19:56.549 it's not that you have so many variations on that, right? 00:19:56.609 --> 00:19:59.009 So you talked about percussive tool use. 00:19:59.249 --> 00:20:03.529 And probing. And then there's probing and sponging, I think you mentioned. 00:20:03.529 --> 00:20:09.309 Yeah, sometimes sponging and a few other things. scraping and using a tool as 00:20:09.309 --> 00:20:12.609 an extension of the arm to pull something in as in. 00:20:12.709 --> 00:20:16.789 But are there common features among these forms of tool use? 00:20:16.949 --> 00:20:20.429 Well they are structurally simple forms of tool use. 00:20:20.949 --> 00:20:27.289 So an object held in the hand is used to create a force relationship, 00:20:27.469 --> 00:20:31.709 a spatial force relationship with something out in front but it's a single order 00:20:31.709 --> 00:20:35.609 kind of relationship. It's the tool to one other thing. 00:20:35.949 --> 00:20:42.689 So it's not the tool to something else with joints and then another thing. And it's not bimanual. 00:20:43.889 --> 00:20:50.109 It's a relatively simple form of tool use in terms of the number of spatial 00:20:50.109 --> 00:20:56.689 relations that have to be produced and have to be monitored and have to be produced 00:20:56.689 --> 00:20:59.089 concurrently. So they're generally producing one. 00:20:59.349 --> 00:21:04.949 Right. But then in terms of their, if you'd characterize tool use in these animals 00:21:04.949 --> 00:21:09.089 in terms of their complexity, are there any patterns that emerge in that? 00:21:10.649 --> 00:21:15.949 Well, there are different metrics for complexity. Because we have no single 00:21:15.949 --> 00:21:20.569 theory guiding our investigation of tool use, people arrive at different metrics 00:21:20.569 --> 00:21:22.969 that make sense for their particular purpose. 00:21:23.309 --> 00:21:27.669 So sometimes people are interested in the sequences of actions. 00:21:28.009 --> 00:21:32.069 Sometimes they're interested in the hierarchical organization of actions, 00:21:32.169 --> 00:21:35.729 that the sequence has to be done in a certain order for things to work. 00:21:36.069 --> 00:21:41.529 Sometimes people are interested in the number of tools used to achieve a single 00:21:41.529 --> 00:21:43.669 goal. So they talk about a toolkit. 00:21:44.649 --> 00:21:48.129 There are probably a few others that I listed in my talk that are not coming 00:21:48.129 --> 00:21:51.149 to my mind at this moment. Well, sequence, number of actions, 00:21:51.509 --> 00:21:54.529 hierarchical organization, selection and transport of materials. 00:21:54.909 --> 00:21:56.649 Yeah, which we already talked about a little bit. And the number and nature 00:21:56.649 --> 00:21:58.849 of spatial relations. And the number and nature of spatial relations. 00:21:59.129 --> 00:22:05.589 Yeah. So if you think about those characteristics, we know that at least…. 00:22:07.288 --> 00:22:11.668 Well, we know best for capuchins and for chimpanzees that they will transport 00:22:11.668 --> 00:22:13.488 materials, both the objects, 00:22:13.748 --> 00:22:18.808 in this case, it's percussive tool use, and chimpanzees also for probic tool 00:22:18.808 --> 00:22:22.488 use, that they will transport the tool to the site of use. 00:22:22.968 --> 00:22:27.828 And they also, in the case of nut cracking, they will transport the nut to the 00:22:27.828 --> 00:22:30.828 site of the anvil. So there is transport happening. 00:22:31.588 --> 00:22:38.328 The details of how far they transport and how selective they are about what 00:22:38.328 --> 00:22:44.428 they transport are being investigated empirically, and I can't give you a lot of detail. 00:22:44.588 --> 00:22:49.608 We know that chimpanzees will transport hammerstones up to 100 meters or so, 00:22:49.728 --> 00:22:54.228 and we know that the same is true for capuchins, although we haven't done the 00:22:54.228 --> 00:22:58.648 careful examination of that that It has been recently carried out by Giulia 00:22:58.648 --> 00:23:01.528 Sirianni for the chimpanzees. 00:23:01.868 --> 00:23:05.908 So that's something we need to work on with the capuchins, I can't tell you. 00:23:05.948 --> 00:23:09.808 But I've seen them carry tools at least 80 meters. 00:23:10.028 --> 00:23:13.228 So, I mean, I don't think there's a big difference between the chimps and the 00:23:13.228 --> 00:23:15.428 capuchins in that domain. 00:23:16.708 --> 00:23:21.408 They are selective in the tools they pick up and bring. 00:23:22.208 --> 00:23:25.868 And this is when they are far enough away from an anvil that they can't have 00:23:25.868 --> 00:23:27.748 the anvil in view when they're doing it. 00:23:27.808 --> 00:23:30.888 So there is some prospective selection of materials. 00:23:31.348 --> 00:23:36.468 And that's true in capuchins and chimpanzees. Probably also true in Burmese 00:23:36.468 --> 00:23:40.368 macaques, although that's been discovered much more recently. 00:23:40.408 --> 00:23:44.328 And so we don't know as much about that group. Right. 00:23:44.588 --> 00:23:51.928 But so then in the actual data you were discussing was very much derived from Capuchin monkeys. 00:23:52.348 --> 00:23:57.268 Exactly. My own knowledge is about Capuchin monkeys. Which seem a rather extraordinary 00:23:57.268 --> 00:23:59.988 type of monkey, I have to say. 00:24:00.108 --> 00:24:01.928 I mean, so you were telling us they were getting fairly old, 00:24:02.148 --> 00:24:07.108 have large brains, also have a fairly long period of, let's say, 00:24:07.208 --> 00:24:14.668 juvenescence and long periods also of, let's say, instruction and training, right? 00:24:14.788 --> 00:24:20.928 So what are sort of for you the properties of tool use in these capuchin monkeys 00:24:20.928 --> 00:24:24.228 that stand out and how have you assessed those properties? 00:24:25.168 --> 00:24:30.588 Well, when we first discovered this, first of all, we couldn't believe our good fortune. 00:24:30.688 --> 00:24:37.148 We could hardly believe our eyes, because it's truly impressive to watch, really. 00:24:39.534 --> 00:24:45.214 And what I was struck by immediately is that it's very skillful. 00:24:45.274 --> 00:24:50.114 It is extremely skillful. For one thing, it is physically very strenuous. 00:24:50.314 --> 00:24:54.614 So these are relatively small monkeys weighing two or three or four kilos in 00:24:54.614 --> 00:24:56.814 adulthood. And of course, the juveniles are smaller. 00:24:57.114 --> 00:25:04.814 And they're picking up stones to crack very resistant palm nuts that they place on an anvil. 00:25:04.874 --> 00:25:08.274 So there's a nut on the anvil. And then the monkey, this little monkey, 00:25:08.414 --> 00:25:13.154 is picking up a stone that on average weighs at least half its body weight. 00:25:13.254 --> 00:25:17.694 It's about a kilo. It's the normal weight of an average weight of a hammerstone in our area. 00:25:18.514 --> 00:25:23.554 And they are lifting it shoulder or head height or sometimes even over the head 00:25:23.554 --> 00:25:28.714 and bringing it down with great force in a directed way, 00:25:28.874 --> 00:25:32.054 in a controlled way, on this nut, which is relatively large, 00:25:32.114 --> 00:25:33.674 but it's still a fairly small target. 00:25:34.194 --> 00:25:38.594 So they're bringing down this very heavy stone on top of the nut, 00:25:38.634 --> 00:25:41.934 and they don't want to have the nut roll away, and they don't want to have the 00:25:41.934 --> 00:25:44.774 stone fall off the anvil, and they don't want to hit their toes, 00:25:44.974 --> 00:25:47.034 and they don't want to harm their hands. 00:25:47.254 --> 00:25:50.814 And I can tell you that when humans try to do this, we're much bigger. 00:25:51.014 --> 00:25:54.914 We can generate a lot of force with a stone. We are actually, 00:25:55.134 --> 00:25:59.534 when we are novices, which most of the research team is novice at cracking nuts, 00:25:59.674 --> 00:26:02.914 we are are not good at it at all and after three 00:26:02.914 --> 00:26:05.934 strikes our hands hurt because we're hanging 00:26:05.934 --> 00:26:09.074 on to the stone tightly when it 00:26:09.074 --> 00:26:15.314 strikes the nut and the rebound force hurts so after a few strikes people say 00:26:15.314 --> 00:26:19.874 well i think i'm done now and they haven't cracked the nut so but the monkeys 00:26:19.874 --> 00:26:25.894 have have worked out a strategy to cope with this they do it repeatedly they're 00:26:25.894 --> 00:26:27.614 they're they're not bruising their hands, 00:26:27.694 --> 00:26:32.194 they don't leave the anvil, you know, shaking their hands as if they hurt or something. 00:26:32.294 --> 00:26:39.114 So they are obviously managing the production of force in a precise trajectory 00:26:39.114 --> 00:26:42.174 and monitoring in some way, 00:26:42.254 --> 00:26:48.354 monitoring the position of the stone and the force that should be applied to the nut. 00:26:48.879 --> 00:26:53.039 And doing this all in a way that is not evident when you first see it, 00:26:53.079 --> 00:26:56.279 but you know that there's something like that going on because the whole system 00:26:56.279 --> 00:26:58.959 is so smooth and so beautiful to watch. Right. 00:26:59.659 --> 00:27:03.679 But then in some sense, what you also showed us is these monkeys are real experts 00:27:03.679 --> 00:27:06.299 in this because they trained for quite a while. Yes, they have. 00:27:06.519 --> 00:27:10.059 So how does this training process exactly work? 00:27:10.819 --> 00:27:17.079 Well, it's self-initiated and self-supported in the sense that there is an intrinsic 00:27:17.079 --> 00:27:21.239 motivation to manipulate objects and especially to percuss objects. 00:27:21.539 --> 00:27:23.859 Which even very young monkeys will do. 00:27:23.959 --> 00:27:29.879 And it's part of their normal foraging, so they do it all throughout their lives as part of normal life. 00:27:30.119 --> 00:27:35.919 But when it becomes focused on nuts and on stones, initially the young monkeys, 00:27:36.119 --> 00:27:39.199 the very young monkeys, are working directly with the nuts. 00:27:39.199 --> 00:27:44.939 They're not big enough to pick up stones, and they don't really have the skill 00:27:44.939 --> 00:27:48.399 to put the nut down and pick up the stone and strike the nut. 00:27:48.479 --> 00:27:49.979 So they're initially focusing on the 00:27:49.979 --> 00:27:54.519 nut itself, and there's just a lot of exploration of the nut in the hands. 00:27:54.579 --> 00:27:57.439 They're rolling it, they're knocking it, they're sweeping it around on the top 00:27:57.439 --> 00:28:01.179 of the surface, and doing many things with the nuts. We've seen monkeys juggle 00:28:01.179 --> 00:28:03.439 with nuts a little bit, just kind of holding them up. 00:28:03.579 --> 00:28:07.899 I mean, we've seen monkeys take the nut and stick it in a little knot in a tree, 00:28:07.999 --> 00:28:09.299 in and out, in and out, in and out. 00:28:09.339 --> 00:28:12.399 I mean, anything you can do with a nut in a sort of playful, 00:28:12.499 --> 00:28:14.379 generative way, they will do that. 00:28:14.519 --> 00:28:17.779 Sooner or later, a monkey will do that. They don't all do all these things, 00:28:17.919 --> 00:28:22.139 but if you sit there and watch them long enough, you see amazing combinations 00:28:22.139 --> 00:28:25.579 of things that make no sense initially, but they're all part of play. 00:28:25.579 --> 00:28:31.379 And then the young monkeys, when they are between one and two years old and 00:28:31.379 --> 00:28:34.439 they're spending quite a bit of time on the ground, about a third of their time 00:28:34.439 --> 00:28:37.399 on the ground, as do the older individuals, all the adults, 00:28:37.599 --> 00:28:43.039 they are attracted to places where adults are cracking. 00:28:43.892 --> 00:28:49.452 And from the cracking activity of others, there is an accumulation of artifacts, 00:28:49.652 --> 00:28:54.232 of debris, nutshells, and the stones that were used because the stones are typically 00:28:54.232 --> 00:28:56.132 left on the anvil. They're not carted away. 00:28:56.292 --> 00:29:01.352 So the anvil and the stone are relatively constant features and the nutshells 00:29:01.352 --> 00:29:05.372 are there and the nutshells don't degrade. So they're there for a long time. 00:29:05.672 --> 00:29:11.212 So a young monkey in the vicinity of others that are cracking can see and can hear. 00:29:11.272 --> 00:29:14.812 And it's a very dramatic activity. It's attention grabbing. 00:29:14.912 --> 00:29:17.712 You can't just not know that your neighbor is cracking a nut. 00:29:17.852 --> 00:29:20.692 You hear it and you see it. It's a whole body motion. 00:29:21.292 --> 00:29:26.072 It's dramatic. So the young monkeys see and hear this activity. 00:29:26.392 --> 00:29:30.792 They see the adults eating. They can also smell what is going on. 00:29:30.792 --> 00:29:36.792 And they also themselves sample the bits of nuts that are still in the shells 00:29:36.792 --> 00:29:37.892 because there are shells around. 00:29:38.032 --> 00:29:42.152 And the adults are quite tolerant of the very young monkeys near them at the 00:29:42.152 --> 00:29:45.632 anvil site. They allow them to be very close and watch. 00:29:45.832 --> 00:29:49.472 And even when they're done cracking to come up and collect bits, 00:29:49.652 --> 00:29:53.312 we call that scrounging. So there is a certain amount of scrounging. 00:29:53.572 --> 00:30:00.772 So the young ones are, I would say, inducted. They're into the cult of nutcracking, 00:30:00.812 --> 00:30:04.952 and they're interested in all these materials and in this place. 00:30:05.052 --> 00:30:08.712 So they are drawn to the place that has the appropriate materials, 00:30:08.832 --> 00:30:12.112 and they are intrinsically motivated to interact with these materials, 00:30:12.292 --> 00:30:15.332 and it proceeds from there. Okay. 00:30:16.048 --> 00:30:20.628 So the learning you're describing is very much sort of the infants exploring 00:30:20.628 --> 00:30:26.448 in a context in which nutcracking is going on. It's a socially supported context. 00:30:27.008 --> 00:30:31.948 And one of your theoretical frameworks is the Gibsonian ecological psychology 00:30:31.948 --> 00:30:40.108 in which the notion of the affordances that an object might have for behavior is very important. 00:30:40.108 --> 00:30:47.028 And the famous example is that a doorknob affords turning, so that rather than 00:30:47.028 --> 00:30:50.608 necessarily focusing on the properties of the doorknob, what you learn about 00:30:50.608 --> 00:30:52.988 it is that if you turn it, the door opens. 00:30:53.548 --> 00:30:57.948 So is that framework useful for you in thinking about what the monkeys are learning? 00:30:58.228 --> 00:31:02.568 It is. I don't think that they think very much about what the stone is useful 00:31:02.568 --> 00:31:07.988 for outside of nutcracking, although they sit on them. But, you know, they're not. 00:31:09.268 --> 00:31:15.508 Anyway, it seems to me that when they are interacting with stones initially and with nuts, 00:31:15.788 --> 00:31:21.168 they are, certainly when they're handling nuts, they are learning about the 00:31:21.168 --> 00:31:25.748 affordances of the nut for direct percussion, but also how it moves in their 00:31:25.748 --> 00:31:27.308 hand and how it moves on a surface. 00:31:27.548 --> 00:31:33.628 Right, yeah. It rolls and they eventually have to manage that feature of nuts 00:31:33.628 --> 00:31:37.328 because when you put it on an anvil and strike it, it's going to roll or fly 00:31:37.328 --> 00:31:40.548 off the anvil unless it's in a relatively stable position, 00:31:40.728 --> 00:31:45.048 which they achieve by putting the nut into a pit and by placing it specifically 00:31:45.048 --> 00:31:47.448 in a certain orientation in the pit. 00:31:47.448 --> 00:31:53.668 So I was wondering if the young animals play with stones, and if there's some 00:31:53.668 --> 00:31:59.148 qualitatively qualitative differences between their play behavior with stones as compared to nuts. 00:31:59.348 --> 00:32:01.608 We don't have great data on that. 00:32:02.488 --> 00:32:06.748 So we have seen them. They do also strike stones directly. 00:32:07.008 --> 00:32:11.008 They strike nuts directly far more often. This makes sense to me because the 00:32:11.008 --> 00:32:14.808 nut is actually their goal object, so to speak. The stone is... 00:32:15.463 --> 00:32:19.023 Secondary thing. So they're more interested in the nuts than in the stones, 00:32:19.103 --> 00:32:22.943 but they do also strike stones directly. 00:32:23.383 --> 00:32:30.563 So the combination of the nut and the stone, I think they are assisted in learning 00:32:30.563 --> 00:32:32.923 that from hanging around the adults. 00:32:33.403 --> 00:32:37.063 Also, the stones that the adults use as hammer stones, 00:32:37.363 --> 00:32:40.883 especially rather soon after they've used them, 00:32:40.963 --> 00:32:47.263 they still have a sort of oily residue from the nut shell and if they've cracked 00:32:47.263 --> 00:32:51.923 a nut sometimes some of the residue of the kernel of the nut is also on the 00:32:51.923 --> 00:32:54.263 stone so they smell good they smell like nuts. 00:32:54.783 --> 00:33:00.543 So the so the young ones both see the adults using the stone on the nut and 00:33:00.543 --> 00:33:05.103 the stones smell like nuts and they're on the anvil or near the anvil and they're 00:33:05.103 --> 00:33:08.403 right there with all the nut shells so there's a lot of association 00:33:08.603 --> 00:33:12.583 of the stone with the nut cracking area and activity, 00:33:12.843 --> 00:33:16.883 even if the young ones are not themselves able to pick up the stone and move it. 00:33:16.943 --> 00:33:22.963 They will often, though, take the nut and strike it on the stone. This is rather common. 00:33:23.183 --> 00:33:27.083 The little ones do quite a lot of that. They do more direct percussion of nut 00:33:27.083 --> 00:33:31.543 onto the anvil, but they will also just simply take the nut and strike it on 00:33:31.543 --> 00:33:35.083 the stone, which is the closest they can get to picking up the stone and striking 00:33:35.083 --> 00:33:36.743 the nut, because they can't pick the stone up. 00:33:36.903 --> 00:33:41.663 And then does the combination of anvil, nut, and stone come later? 00:33:41.963 --> 00:33:47.363 It does appear later developmentally. And what you see is a young one on the 00:33:47.363 --> 00:33:50.343 anvil with a nut, and it puts the nut down, and it strikes the nut up and down. 00:33:50.463 --> 00:33:53.163 But one thing that's actually, I didn't have time to talk about this in my talk 00:33:53.163 --> 00:34:00.803 today, is that in previous work by Briseida Hacende in Sao Paulo. 00:34:01.564 --> 00:34:08.724 And she did a longitudinal study of the onset of nut cracking in a semi-free 00:34:08.724 --> 00:34:14.084 population of monkeys, provisioned monkeys in a regenerating forest in a park 00:34:14.084 --> 00:34:15.424 outside of Sao Paulo City. 00:34:15.764 --> 00:34:22.244 And in that population, they crack small palm nuts, Cyagris palm nuts that are 00:34:22.244 --> 00:34:23.684 sort of the size of an acorn. 00:34:23.804 --> 00:34:28.684 So they can do that with a much smaller stone, and they use much less force. 00:34:28.684 --> 00:34:32.964 So in that situation, the young monkeys that she was following, 00:34:33.264 --> 00:34:39.744 the parallels with the monkeys that we watch in Boa Vista are perfect. 00:34:40.004 --> 00:34:42.944 I mean, they're doing the same things. Although the smaller size of the nuts 00:34:42.944 --> 00:34:47.224 and the smaller size of the stones gives those monkeys an advantage. 00:34:47.404 --> 00:34:49.784 They can manage these things when they're smaller. 00:34:50.044 --> 00:34:55.284 So they have a bit of a temporal advantage in terms of the the physical strength 00:34:55.284 --> 00:34:56.664 they need to manage the stones. 00:34:56.884 --> 00:35:02.464 But in that population, what she found was that the young monkeys. 00:35:05.464 --> 00:35:10.924 The last thing to appear in the whole sequence of cracking is to put the nut 00:35:10.924 --> 00:35:12.364 on the anvil and then release it. 00:35:13.224 --> 00:35:16.704 So think about it. If you're an arboreal monkey and you've got something you 00:35:16.704 --> 00:35:21.684 want, the last thing you want to do is let go of it. It's just going to fall to the ground. 00:35:22.684 --> 00:35:27.064 So on the ground, if you release something, it stays there. It might move a 00:35:27.064 --> 00:35:28.104 little, but it just stays there. 00:35:28.184 --> 00:35:33.484 And they have to learn to allow the thing they're interested in to be released 00:35:33.484 --> 00:35:36.564 and then take the stone and hit it. 00:35:36.804 --> 00:35:41.324 And at that point, they have to switch attention from one object to another. 00:35:41.624 --> 00:35:46.464 So you're still interested in the nut, but you have to let go of it and leave contact with it. 00:35:46.504 --> 00:35:50.444 And then you have to pick up a stone and then hit it. So it's an integrative 00:35:50.444 --> 00:35:54.624 attentional problem that you have to bring the stone into the, 00:35:55.317 --> 00:35:59.837 zone of attention, if you will, while you've still got the nut there. 00:36:00.437 --> 00:36:04.797 And this is the hardest part for the capuchins. So it's interesting that for 00:36:04.797 --> 00:36:06.597 chimpanzees, I think it's different. 00:36:07.857 --> 00:36:13.477 Chimpanzees don't do a lot of percussion. They do far less percussion in just 00:36:13.477 --> 00:36:15.557 an exploratory way than capuchins do. 00:36:16.157 --> 00:36:21.237 And for the young chimp who's learning to crack stones, for them, 00:36:21.297 --> 00:36:25.217 the difficult The difficult part is cracking with a stone. 00:36:25.457 --> 00:36:29.777 It's the percussion act that they're not really likely to perform. 00:36:29.957 --> 00:36:33.937 That's the least likely part of their sequence is to pick up the stone and whack something. 00:36:34.337 --> 00:36:37.877 For the capuchins, the least likely part of the sequence is to leave the nut 00:36:37.877 --> 00:36:39.957 down on the anvil and take your hand off it. 00:36:40.397 --> 00:36:46.537 So I think they have different developmental challenges in learning this sequence. 00:36:46.537 --> 00:36:51.217 And it means that also these elements will appear later in the developmental process Right. 00:36:52.777 --> 00:36:55.217 Differentially for the capuchin and the chimpanzees. Right. So the last thing 00:36:55.217 --> 00:36:59.557 to appear is that you put the nut down and you let it go and you pick up the stone and hit it. 00:36:59.677 --> 00:37:04.857 And we often see, for example, young ones will have two pieces of shell or two 00:37:04.857 --> 00:37:08.157 nuts or something and they'll be on the anvil and they'll be hitting one and 00:37:08.157 --> 00:37:11.077 then they pick that one up. 00:37:11.137 --> 00:37:14.157 But then they have to hit this one and they're going back and forth like they 00:37:14.157 --> 00:37:18.557 can't figure out which one to hit because they can't figure out which one to let go of. 00:37:19.257 --> 00:37:25.657 But now if we focus on this learning phase, right? So what are the minimal ingredients 00:37:25.657 --> 00:37:30.457 with which this monkey must be thrown in the world to actually start to learn this? 00:37:30.797 --> 00:37:35.477 And the point is that if you talk about an intrinsic motivation, 00:37:35.737 --> 00:37:38.157 okay, that's fine, but an intrinsic motivation for what? 00:37:38.577 --> 00:37:41.957 Yeah. Right? So what are these minimal ingredients that are required? 00:37:43.362 --> 00:37:47.862 Well, it's conjecture here. Of course. I'm designing a monkey. 00:37:48.062 --> 00:37:56.642 So I think that what they bring to this task is an intrinsic interest in interacting 00:37:56.642 --> 00:38:02.102 with objects and especially in percussion, which is part of their normal foraging activity. 00:38:02.902 --> 00:38:07.502 And it's part of exploring their world to know even what to eat and how to do 00:38:07.502 --> 00:38:11.782 it. So you mean the infant cappuccino monkey would basically grab any object 00:38:11.782 --> 00:38:15.322 of a certain size and just cross it on? Yeah, they do. 00:38:15.622 --> 00:38:20.302 Anything that can be banged, they try that. Leaves, twigs, anything. 00:38:21.922 --> 00:38:28.622 So they are interested from a very young age, actually from the age at which 00:38:28.622 --> 00:38:34.122 they have enough postural stability to take one arm and swing it forcefully. 00:38:34.202 --> 00:38:37.422 That's when they begin to bang. as soon as they can, basically. 00:38:38.402 --> 00:38:46.462 So that's a key ingredient, because if you don't have that initial action to 00:38:46.462 --> 00:38:50.882 work on, you're never going to get nutcracking without at least some of that. 00:38:51.182 --> 00:38:53.522 And capuchins have a lot of that one. 00:38:54.482 --> 00:39:03.742 So then secondly, you have to have enough motivation to do Once you have an 00:39:03.742 --> 00:39:08.162 instrumental goal, you have to have enough interest in, 00:39:08.874 --> 00:39:13.094 working towards that goal for a very long time, because for them, 00:39:13.094 --> 00:39:19.434 the learning period where they're doing this activity in various forms is years. 00:39:19.614 --> 00:39:21.474 It's literally something like 00:39:21.474 --> 00:39:26.314 three or four years before they can actually crack a nut very effectively. 00:39:26.614 --> 00:39:32.434 So in this long period of time, they must generate a lot of percussion, 00:39:32.634 --> 00:39:35.594 and they must enjoy it enough to They keep doing it. 00:39:35.834 --> 00:39:38.774 They have to get their 10,000 hours or so. 00:39:39.094 --> 00:39:43.794 But then combined with that, now to get back to the notion of affordance, 00:39:43.954 --> 00:39:50.414 you also indicated that the traces of nutcracking are around them, right? 00:39:50.494 --> 00:39:53.134 So they will see the shells, they 00:39:53.134 --> 00:39:56.914 might see the anvil, they might see the pits and the stones and so on. 00:39:57.574 --> 00:40:03.734 How much is that residue or these traces of nutcracking also affording the learning 00:40:03.734 --> 00:40:05.374 process? So it's really a trigger. 00:40:05.614 --> 00:40:11.994 Yeah. I think they're a strong support. Our data show that being around an anvil 00:40:11.994 --> 00:40:17.454 is associated with a very large increase in manipulation of nuts. 00:40:17.574 --> 00:40:20.594 And it doesn't have to be that way because the nuts are very portable, 00:40:20.714 --> 00:40:24.674 especially the shells. By nut, I mean nut or nutshell in this case. 00:40:24.994 --> 00:40:29.554 And that's very portable. So if the infants wanted to, if the juveniles wanted 00:40:29.554 --> 00:40:32.834 to, they can pick up a piece of nutshell and they can go somewhere else with 00:40:32.834 --> 00:40:36.914 it. They don't have to stay right by the anvil and manipulate the thing near an anvil. 00:40:36.994 --> 00:40:41.874 And in our data, the kids are manipulating nut materials, nut shells, 00:40:42.094 --> 00:40:47.694 nuts, at especially high rates around the anvils. 00:40:47.794 --> 00:40:51.914 So the anvil is a place where you go when you feel like manipulating nuts, you go there. 00:40:51.994 --> 00:40:55.054 Or if you happen to go to an anvil, then you begin to manipulate nuts. 00:40:55.134 --> 00:40:57.374 So it's kind of a trigger for the activity. 00:40:57.814 --> 00:41:00.354 And so the fact that these are enduring artifacts... 00:41:01.376 --> 00:41:06.716 It certainly supports it. And this is actually not so unlike a human situation 00:41:06.716 --> 00:41:14.296 where we have artifacts of our cultures everywhere in our homes and in our towns. 00:41:14.396 --> 00:41:21.556 And kids encounter chairs everywhere and they encounter common tools, cups, glasses. 00:41:21.996 --> 00:41:25.976 But in the environment in which such a population of monkeys lives, 00:41:26.196 --> 00:41:30.336 they would then have a few anvils to which they transport the nuts. 00:41:31.376 --> 00:41:35.456 Or they just find a nut and then find an appropriate spot where they can crack it? 00:41:35.856 --> 00:41:41.256 Both. See, if you find a nut somewhere, you would go to the nearest anvil, 00:41:41.336 --> 00:41:43.476 because you have to go somewhere that has a hammerstone. 00:41:43.656 --> 00:41:47.356 So the hammerstone is the limiting resource here, not the anvil per se, 00:41:47.396 --> 00:41:51.596 because there are many possible anvil sites. 00:41:51.756 --> 00:41:57.196 You need a relatively flat, hard surface. You can use virtually any boulder, 00:41:57.316 --> 00:42:03.136 or sometimes a fallen log will also serve if it has a broad surface. 00:42:03.856 --> 00:42:10.196 But the hammerstones are rare because the predominant stone in that area is 00:42:10.196 --> 00:42:14.296 a relatively soft sandstone, and that's unsuitable for cracking nuts. 00:42:14.376 --> 00:42:17.756 It just breaks in your hand. If you take a big chunk of sandstone and whack 00:42:17.756 --> 00:42:25.396 it, it just falls apart. part. So they are mainly using siltstone and ironstone and quartzite cobbles. 00:42:25.676 --> 00:42:31.436 Quartzite cobbles are washed in from some ancient flood who knows how many eons 00:42:31.436 --> 00:42:33.416 ago, and probably more than one. 00:42:33.576 --> 00:42:36.936 And they're in layers in the sandstone. 00:42:37.136 --> 00:42:43.796 And as the ridges erode, the cobbles are exposed, and they either are just exposed 00:42:43.796 --> 00:42:46.096 in situ or eventually they fall down. 00:42:46.296 --> 00:42:49.196 So in the transition zone between the 00:42:49.196 --> 00:42:52.296 cliff and in the talus area where the where the 00:42:52.296 --> 00:42:56.416 um the the boulder fields 00:42:56.416 --> 00:42:59.936 are for where the sandstone has eroded and fallen and 00:42:59.936 --> 00:43:03.816 where there are ephemeral streams in the rainy season there there it can rain 00:43:03.816 --> 00:43:08.896 hard and then there are these uh channels where water comes down off the off 00:43:08.896 --> 00:43:15.716 the cliffs and the plateaus down into the valley and um there are um uh quartzite 00:43:15.716 --> 00:43:17.356 cobbles pebbles that accumulate there. 00:43:17.476 --> 00:43:21.916 They're mainly small little pebbles, but there are also occasionally larger 00:43:21.916 --> 00:43:25.216 stones, and the monkeys use the larger stones to crack the nuts. 00:43:25.256 --> 00:43:31.156 But then do you see that in their migration patterns these monkeys would sort of consolidate. 00:43:32.262 --> 00:43:36.562 The locations where they find these stones or they are migration patterns are 00:43:36.562 --> 00:43:40.442 not dependent on the possibility to find such hammer stones. 00:43:40.482 --> 00:43:44.002 Their home range is not dependent on where the anvils are, but there are many 00:43:44.002 --> 00:43:46.062 anvils scattered around in their home range. 00:43:46.482 --> 00:43:52.762 But the stones, the hammer stones. The hammer stones are transported to an anvil site. 00:43:52.942 --> 00:43:58.342 Okay. So they may be transported a very short distance if there is a suitable 00:43:58.342 --> 00:44:01.922 boulder right next to this stream and you find a hammerstone in the stream, 00:44:02.002 --> 00:44:04.382 then you just go two or three meters and you're at the anvil. 00:44:04.902 --> 00:44:11.062 But we also find hammerstones in very unlikely places like the top of the ridge 00:44:11.062 --> 00:44:16.442 and somewhere off in the, you know, distant from any water source. 00:44:16.582 --> 00:44:19.802 So they transport these stones around as well. That's what I was wondering about, 00:44:19.882 --> 00:44:25.762 because you could imagine that in this Capuchin culture, the scarce resource is the hammerstone. 00:44:25.942 --> 00:44:29.602 So you can imagine when they migrate that they would actually carry hammerstones along. 00:44:29.782 --> 00:44:31.882 Well, they don't migrate. They don't migrate. Let me correct that. 00:44:31.962 --> 00:44:36.402 They have a home range that they move around during the day, 00:44:36.582 --> 00:44:38.042 and they cover the home range. 00:44:38.202 --> 00:44:41.382 They travel into different parts of their home range periodically. 00:44:41.382 --> 00:44:49.062 So, they travel a few kilometers a day, perhaps, overall, linear distance. 00:44:49.922 --> 00:44:55.202 And they sometimes take a hammerstone with them when they leave an anvil. 00:44:55.302 --> 00:44:58.482 But they do that, especially if there is some competition. 00:44:58.482 --> 00:45:05.182 So if a juvenile or a subordinate adult is on an anvil with a hammerstone and 00:45:05.182 --> 00:45:08.262 is about to be displaced by a more dominant individual, 00:45:08.582 --> 00:45:14.982 if the individual that's got to leave is able to do so, it will take that hammerstone. 00:45:14.982 --> 00:45:19.602 If the hammerstone is too heavy, you're just stuck, you just have to leave and 00:45:19.602 --> 00:45:20.842 you leave your hammerstone behind. 00:45:21.602 --> 00:45:27.682 In any case, sometimes we see individuals transporting hammerstones from one anvil to another. 00:45:27.982 --> 00:45:33.142 And sometimes we understand a competitive reason for it and sometimes we don't know why they do it. 00:45:33.847 --> 00:45:39.327 So we're using the word Capuchin culture here to describe what's happening. 00:45:39.567 --> 00:45:44.807 And when we think of that in human terms, we also think of things like cultural transmission. 00:45:45.047 --> 00:45:51.627 So something might be invented in one place, but it rapidly spreads as other 00:45:51.627 --> 00:45:55.087 tribes copy that initial invention. 00:45:55.587 --> 00:46:00.187 I mean, do you think that there is cultural transmission between Capuchin? 00:46:00.187 --> 00:46:06.327 Or is it much more something that they will discover for themselves? 00:46:06.627 --> 00:46:10.727 Or do they have to see it? Let me back up to the word culture for a moment. 00:46:10.867 --> 00:46:12.487 Because that's a loaded word. 00:46:12.747 --> 00:46:17.007 That's what I was thinking. I brought it up as well, right? So I'm fully responsible for some words. 00:46:17.127 --> 00:46:22.227 I use the word tradition because it avoids some of the extra meaning that's 00:46:22.227 --> 00:46:25.547 associated with that word from an anthropocentric perspective. 00:46:25.547 --> 00:46:28.627 Perspective because of course there are many components that people 00:46:28.627 --> 00:46:32.047 think are critical to culture that 00:46:32.047 --> 00:46:35.927 in humans that are not evident in capuchins 00:46:35.927 --> 00:46:39.727 okay could you elaborate well for example religion symbolic 00:46:39.727 --> 00:46:45.607 systems of i don't know there are many others that that are i'm not an anthropologist 00:46:45.607 --> 00:46:49.987 so you have to forgive me if i don't have their list but but and and anthropologists 00:46:49.987 --> 00:46:54.087 also have a tough time agreeing on exactly what is in culture but in any case 00:46:54.087 --> 00:46:58.347 it's a longer list than what we can say is present in the capuchins, 00:46:58.387 --> 00:47:02.447 or chimpanzees, or any ape, except humans. 00:47:02.607 --> 00:47:06.607 Okay. So in any case, let's talk about traditions. But the question still stands. 00:47:07.447 --> 00:47:15.027 If this is a socially aided learning system, is it likely that this particular 00:47:15.027 --> 00:47:19.847 behavior would be evident in a group without these social supports for learning? 00:47:20.434 --> 00:47:24.874 That's your question? Yeah. And is it possible that this is socially transmitted? 00:47:25.134 --> 00:47:27.654 It's absolutely possible. And I think it's absolutely the case. 00:47:27.754 --> 00:47:29.554 And that's exactly what our data show. 00:47:29.814 --> 00:47:35.374 That is, they don't show what happens if an individual does not have social 00:47:35.374 --> 00:47:39.894 support, because we don't take monkeys out of their social group and watch them 00:47:39.894 --> 00:47:41.414 grow up without partners. 00:47:41.594 --> 00:47:46.194 But in this natural setting where we have our observational data, 00:47:46.294 --> 00:47:47.974 so we can't assign cause and effect. 00:47:47.974 --> 00:47:52.614 But the pattern seems to be that the young monkeys are growing up in this socially 00:47:52.614 --> 00:47:54.034 supportive setting with all 00:47:54.034 --> 00:47:57.874 the right materials and all the right social prompts to do these things. 00:47:57.874 --> 00:48:03.354 And they have the time to practice over a lengthy, over years, 00:48:03.594 --> 00:48:08.254 and this supports the development of this skill that I think is, 00:48:08.354 --> 00:48:16.454 in the way that they perform it, has to be seen as a kind of extreme skill in 00:48:16.454 --> 00:48:19.494 terms of the difficulty of mastering all these components. 00:48:19.494 --> 00:48:22.334 Components there are other groups of capuchins in other 00:48:22.334 --> 00:48:25.834 places that also display nut cracking and 00:48:25.834 --> 00:48:28.694 i imagine they have their own components of skill 00:48:28.694 --> 00:48:31.494 in what they're doing i i just don't happen to know them as 00:48:31.494 --> 00:48:35.734 well okay but it would suggest the possibility of maybe a lab-based experiment 00:48:35.734 --> 00:48:40.634 where you take a new world monkey species not known to use tools in the wild 00:48:40.634 --> 00:48:44.474 but but you expose them to a tool 00:48:44.474 --> 00:48:50.474 use culture and you could see maybe from observing humans cracking nuts. 00:48:51.274 --> 00:48:55.854 Would a non-tool using new old monkey perhaps pick up that skill? 00:48:56.074 --> 00:48:59.694 No, I can tell you they don't. We've tried that. 00:49:01.154 --> 00:49:06.174 It's not something that monkeys learn by just observing humans. 00:49:06.886 --> 00:49:12.026 Without deep familiarity with the materials involved and deep interest in the 00:49:12.026 --> 00:49:13.806 outcome of the activity. 00:49:14.826 --> 00:49:18.426 And, you know, it would have to be a sort of live-in experience. 00:49:19.086 --> 00:49:22.166 Well, I was thinking of, you know, a sort of a Kansi-like sort of immersion 00:49:22.166 --> 00:49:25.826 in a tool-using environment. 00:49:26.166 --> 00:49:29.626 You know, you're surrounded by them and people are showing you all the time 00:49:29.626 --> 00:49:34.266 and playing with you. You know, in the way that we intensely expose our children 00:49:34.266 --> 00:49:39.506 to the kinds of objects and things that we want them to engage with as they grow older. 00:49:40.266 --> 00:49:46.766 I don't think it would be a success. That is, in the case of capuchin monkeys, 00:49:47.126 --> 00:49:50.506 people have kept them as pets for a long time. 00:49:50.626 --> 00:49:54.346 You know, Native Americans have kept capuchins as pets, and they still do for 00:49:54.346 --> 00:49:57.306 lots of reasons. Sometimes they end up in the pot after a while, 00:49:57.366 --> 00:49:58.466 but we won't talk about that. 00:49:59.666 --> 00:50:07.306 In any case, capuchins that are kept in human homes will sometimes begin to 00:50:07.306 --> 00:50:11.666 use objects for things that people don't intend them to do. 00:50:12.686 --> 00:50:18.106 And they can be trained. This is the basis for a program that you might have 00:50:18.106 --> 00:50:20.686 heard of, Helping Hands, and there have, 00:50:21.526 --> 00:50:25.686 been some other programs where the goal is to use a non-human primate, 00:50:25.746 --> 00:50:32.246 a capuchin monkey In fact, as an aid for a quadriplegic person to do things that require hands, 00:50:32.326 --> 00:50:37.946 like opening the refrigerator and taking a glass out and attaching a straw and something like that. 00:50:37.946 --> 00:50:45.066 And so capuchins can learn to do many things with objects, 00:50:45.506 --> 00:50:52.626 but actually for those training programs, it hasn't been shown that using a 00:50:52.626 --> 00:50:56.346 demonstration model helps in the training at all. 00:50:56.486 --> 00:51:00.426 They use straightforward reinforcement shaping and training. 00:51:01.486 --> 00:51:06.206 So that means in this case, in the literature on the development of skill, 00:51:06.446 --> 00:51:11.366 at least in humans, there's a strong distinction between an imitation-based 00:51:11.366 --> 00:51:14.486 interpretation versus an interaction-based interpretation. 00:51:14.826 --> 00:51:18.506 So I understand from you that if you had to choose, you would say the Capuchin 00:51:18.506 --> 00:51:23.186 acquires the skill very much through interaction and less through imitation. 00:51:23.586 --> 00:51:27.806 Right. Is that correct? Yeah, that's correct, except I would add the proviso by interaction. 00:51:28.246 --> 00:51:33.926 I wouldn't include direct interaction from the more proficient individual with 00:51:33.926 --> 00:51:39.766 the less proficient because there's no teaching or intentional showing. 00:51:40.526 --> 00:51:45.326 It's just in the course of daily life, the kids are exposed to this over and 00:51:45.326 --> 00:51:48.246 over and over again in a supportive setting. Okay. 00:51:48.926 --> 00:51:54.526 And the capuchins have become specialized for tool use away from the other new 00:51:54.526 --> 00:51:56.526 world monkeys, is what I was getting at. 00:51:56.786 --> 00:52:01.466 Yes, that's true. Yeah. And you can see that, I guess, morphologically as well in the... 00:52:03.141 --> 00:52:06.341 The amount of dexterity they have yeah although i wouldn't attribute that to 00:52:06.341 --> 00:52:11.361 tool use because all capuchins have this and only some capuchins species use 00:52:11.361 --> 00:52:17.761 tools so the the uh enhanced mobility of the thumb and and dexterity of the 00:52:17.761 --> 00:52:22.121 fingers that we see in the capuchin monkeys um is um, 00:52:22.861 --> 00:52:29.021 is is i think better associated with their extractive foraging style which they 00:52:29.021 --> 00:52:32.661 are specialized in extraction as well as in tool use. 00:52:32.861 --> 00:52:38.941 So they're really more specialized in foraging, extractive foraging, than anything else. 00:52:39.021 --> 00:52:42.501 And other than that, they're dietary generalists, they're habitat generalists. 00:52:43.201 --> 00:52:49.321 They're very adaptable monkeys. And tool use is one example of an unusual adaptation 00:52:49.321 --> 00:52:52.081 of behavior that they can acquire. 00:52:52.081 --> 00:52:58.241 So these tool-using monkeys, are you able to show that there are other cognitive 00:52:58.241 --> 00:53:01.921 tests, perhaps, on which they do better than some other? 00:53:02.261 --> 00:53:07.201 Is there a program to look at that? Well, first you have to realize that the 00:53:07.201 --> 00:53:12.941 taxonomy of the genus has been shifting under our feet the last few years. Yeah. 00:53:13.061 --> 00:53:20.541 So at the moment, most of the lab colonies that work with tufted capuchin monkeys, 00:53:21.481 --> 00:53:25.041 work with, we always called them Cebus sapella. 00:53:26.121 --> 00:53:30.801 Now we no longer know what they are, so we don't even know exactly what species 00:53:30.801 --> 00:53:31.881 we have for the most part. 00:53:31.921 --> 00:53:36.261 There has to be some further analysis to even know what species we're working with. 00:53:38.529 --> 00:53:40.909 Okay, now what did you ask me? I'm sorry, I lost the train of thought. 00:53:40.909 --> 00:53:44.329 Whether there would be a program to look at more broadly. 00:53:44.569 --> 00:53:49.189 Oh, a cognitive variation across the genus? Oh, a research program, no? 00:53:49.289 --> 00:53:52.229 What would be interesting, 00:53:52.349 --> 00:53:56.389 I think, in the context of particularly this week when we're looking at evolution 00:53:56.389 --> 00:54:03.109 and development was whether these are animals that have evolved tool use as 00:54:03.109 --> 00:54:06.089 part of a cluster of increased cognitive capacity. 00:54:06.089 --> 00:54:08.889 Or is it very much just one thing that's improved? 00:54:09.349 --> 00:54:16.489 Yeah, I wish I could, I wish I knew. And we don't have the, nobody is pursuing 00:54:16.489 --> 00:54:20.829 that at the moment, because what you would need is a colony of, 00:54:21.029 --> 00:54:24.729 you would need to know what form of tufted capuchin you had, 00:54:24.909 --> 00:54:28.569 and then you would need another species that does not use tools. 00:54:28.709 --> 00:54:33.569 And at the moment, what's surprising is that for the past 50 years, 00:54:33.589 --> 00:54:37.289 people have worked with tufted capuchins identified as Cebus apella, 00:54:37.529 --> 00:54:41.829 and our lab studies on tool use have used Cebus apella. 00:54:41.949 --> 00:54:50.649 Now that we have revised the taxonomy, Sapaju apella actually doesn't use tools 00:54:50.649 --> 00:54:54.149 in the wild, and Sapaju libidinosis does. 00:54:54.469 --> 00:54:59.209 So what it would be really grand to do is to have Sapaju to apella, 00:54:59.289 --> 00:55:08.909 the proper apella, and libidinosis, because they do not live in exactly the 00:55:08.909 --> 00:55:12.569 same places, but they border one another. And actually, they... 00:55:13.665 --> 00:55:21.625 They just border one another. And they inhabit rather similar habitat types. 00:55:21.825 --> 00:55:26.985 They're ecologically rather similar. Or anyway, some other species that is morphologically 00:55:26.985 --> 00:55:31.445 quite similar to libidinosis, but is not known to use tools in the wild and 00:55:31.445 --> 00:55:33.285 set up captive colonies of those. 00:55:33.485 --> 00:55:39.545 And we don't have that set up yet. But Dorothy, actually, across all All primatologists 00:55:39.545 --> 00:55:44.005 are not already implicitly running such an experiment as you mentioned this morning. 00:55:44.045 --> 00:55:48.045 Because you say, look, if these animals acquire this skill through interaction 00:55:48.045 --> 00:55:54.385 with the materials and their affordances, it does mean they must have a certain 00:55:54.385 --> 00:55:56.905 creative ability and an ability of insight. 00:55:58.205 --> 00:56:02.325 And what you were describing this morning, if you just look at the way capuchin 00:56:02.325 --> 00:56:07.165 monkeys are kept as compared to chimps, there are some striking differences. 00:56:07.165 --> 00:56:11.065 Differences because these capuchins seem to be very capable in escaping, 00:56:11.285 --> 00:56:12.565 essentially. Well, chimps can too. 00:56:12.885 --> 00:56:16.605 Yeah, I didn't say that you didn't have to lock the cage for chimps. 00:56:16.705 --> 00:56:20.525 I said if you- And they also use tools. Yes, yeah, yeah. 00:56:20.665 --> 00:56:25.905 But if you have capuchins in a cage with a latch that a macaque will not undo, 00:56:26.025 --> 00:56:28.605 the capuchin will undo it unless it's really padlocked. 00:56:29.565 --> 00:56:38.045 What I was trying to get at is that maybe the faculty we want to look at is 00:56:38.045 --> 00:56:42.125 just the creativity to explore an action space, right? 00:56:42.245 --> 00:56:44.825 That's not the key in this case. Would you agree with that? 00:56:45.965 --> 00:56:51.665 Yes, although the clean experiment that was suggested, we have yet to do. 00:56:51.765 --> 00:56:55.225 We haven't done exactly that. That would be interesting to do. 00:56:56.147 --> 00:56:59.547 But an experiment that you have done that you described to us was this one where 00:56:59.547 --> 00:57:03.807 the animal's required to fit an object into a mold. Right, right. 00:57:03.987 --> 00:57:07.107 And they're not able to do that with the more complex shape. 00:57:07.227 --> 00:57:11.867 Right, once you exceed, well, they don't do it very well with one dimension, 00:57:11.967 --> 00:57:14.127 one feature that is just the length of the stick. 00:57:14.307 --> 00:57:17.727 When you add a second dimension that is a cross piece, then they are, 00:57:17.827 --> 00:57:19.447 then they really have trouble. 00:57:19.587 --> 00:57:24.347 And they get there, but it's brute force solution. Yeah. But for example, 00:57:24.347 --> 00:57:28.407 I have not tried myself to do that kind of experiment with, say, squirrel monkey, 00:57:28.647 --> 00:57:34.687 which is, you know, in some ways considered a close relative to the capuchins. 00:57:34.687 --> 00:57:39.667 So, Dorothy, to get to the finish line, two questions. 00:57:39.887 --> 00:57:45.427 So, I mean, it's marvelous work you've been exposing to us about skill, 00:57:45.747 --> 00:57:50.067 tool use in the wild, right, which is extremely hard to study. 00:57:50.267 --> 00:57:55.587 So, given all this experience you have in studying behavior under these ecologically 00:57:55.587 --> 00:58:00.887 realistic conditions, what is really Dorothy's law that we should all adhere 00:58:00.887 --> 00:58:02.667 to in understanding behavior and the brain? 00:58:06.407 --> 00:58:13.967 Um that's a hard one a single law of course i can't have a whole set how about a menu, 00:58:14.967 --> 00:58:19.807 um what's the first item on your menu that that the that the experimenter should 00:58:19.807 --> 00:58:23.467 do that the scientist we should all do it might be advice to students, 00:58:25.087 --> 00:58:30.967 look at the animal look at the behavior look at it in slow motion and look at 00:58:30.967 --> 00:58:34.327 it again Again, that's my advice. Okay, cool. 00:58:35.307 --> 00:58:38.827 So Tony likes traveling, so we're going to send him to your lab four years from now. 00:58:39.347 --> 00:58:44.067 And he's going to check a prediction you're going to share with us today. 00:58:44.147 --> 00:58:48.967 So what's the key specific prediction that you would like to commit yourself 00:58:48.967 --> 00:58:53.527 to today in this domain of tool use in non-human primates? 00:58:55.931 --> 00:59:02.931 I predict that young monkeys who are faced with a challenge of handling a novel stone, 00:59:03.271 --> 00:59:12.151 that the trajectory for becoming expert at using a stone like that, 00:59:12.251 --> 00:59:16.251 the ease of learning to handle this novel stone, 00:59:16.511 --> 00:59:19.731 that there will be a developmental trajectory for that. 00:59:19.731 --> 00:59:28.091 That the skill of handling stones develops slowly over time with a lot of practice, 00:59:28.171 --> 00:59:32.691 and I'm not there to measure all the practice, so I'm just sampling at time points. 00:59:33.091 --> 00:59:34.951 But I predict we're going to 00:59:34.951 --> 00:59:39.251 see that it's not a very complicated prediction in the end. I don't know. 00:59:39.571 --> 00:59:44.171 That's not a great prediction for you. It's not a theory-driven prediction at all. 00:59:44.411 --> 00:59:46.811 He might be disappointed for you, Shona. We're going to see. 00:59:46.811 --> 00:59:49.591 Yeah, if you gave me another five minutes, I might think of another prediction. 00:59:49.951 --> 00:59:52.971 Dorothea Fergesi, thank you very much for this conversation. You're welcome. 00:59:55.611 --> 01:00:02.171 Kind of a wimpy prediction, sorry. 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