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Dr. Laurie Santos is an Associate Professor of Psychology at Yale University. Her research provides an interface between evolutionary biology, developmental psychology, and cognitive neuroscience, exploring the evolutionary origins of the human[…]

Our ability to learn from others is crucial for the evolution of cumulative technologies, but often paralyzes our causal intuition.

Question: Why are monkeys capable of using rudimentary tools, rnbut not more modern technology?

Laurie Santos: Primate researchers are also a little rndisingenuous when they talk about primate tool-use because the kinds of rntools that primates use tend to really impress us. First of all, they rnuse tools, which we didn’t think they did, you know, over 40 years ago. rnNow we see evidence that they use tools in all kinds of contexts.  You rnknow, tools to get food, tools to attract other mates, you know, tools rnto kind of sponge off seeds and climb up trees.  Tools for all kinds of rndifferent things.  They even seem, in some cases, to have tool kits.  rnSo, kits of tools they’ll use for one particular function, or they’ll rnuse for different part of the same tool and multiple different tools.  rnAnd this really impresses us.  But this is kind of the limit of it. You rnknow, there’s nothing like the kinds of complex tools or technologies rnthat we see in humans. 
So, one way to classify the differencern is that primates actually do seem to use tools, you know, ones that arern relatively complicated for other species, but they don’t seem to have rntechnologies in the ways that we do in the sense that they don’t have a rnsort of cumulative evolution of different tool cultures that in some rnsense take on a life of their own where multiple individuals are rncontributing to this.  The kinds of designs that we come up with in one rngeneration get passed on and improved on by the other generation.  rnAgain, you see little bits of this, but nothing at the scale that we rnhave in our own species. 
Why are humans capable of building cumulative technologiesrn while monkeys are not?

Laurie Santos: it’s still arn big puzzle as to why we’re the only species that has cumulative rntechnology in the way that we do.  One answer that seems to be coming uprn might have to do with the way that humans imitate other individuals.  rnSo, there was recently a study by Andy White and his colleagues trying rnto look at the ways that human children imitate a person acting on a rntool, versus the way that chimpanzees imitate. 
rnAnd so the experiment went like this: Both children and chimpanzees werern given a little puzzle box.  It was opaque; they couldn’t see how it rnworked, but they get to watch a human demonstrator it and open it up.  rnAnd the steps to open it up were of two parts.  First it involved a kindrn of tapping the puzzle box on the top in a certain way, and then it rninvolved opening a door and taking out a treat.  So, both kids and rnchimpanzees, after seeing this can follow the experimenter perfectly.  rnSo they do the tapping part open the door, get the treat. 
Now,rn you do the same sort of setup, except instead of the box being opaque, rnit’s now transparent.  And it’s obvious to both the child subjects and rnthe chimpanzees that the whole tapping part of the top is just bogus.  rnLike the tapping doesn’t actually go anywhere, it’s kind of like a falsern top.  So you can see as you’re watching the person do this that you rndon’t need to do this, all you have to do is open the door. 
Whenrn you give this puzzle to chimpanzees, they do what you might expect to rnbe the smart maneuver; they just kind of cut to the chase and open the rndoor and take the treat.  When you do this with human children, however,rn what you find, surprisingly—and perhaps embarrassingly for our rnspecies—is that the human children slavishly imitate the person they rnsee.  So even though they can clearly see that this, you know, poking onrn the top is a stupid gesture, they do it anyway. 
What it rnseems like is that humans really are paralyzed by watching the actions rnof others.  It actually seems to change our causal intuitions about how rndifferent objects work.  This is bad when people do really stupid thingsrn on boxes and open them the wrong way, but it’s great for the cumulativern evolution of technology because it means that you don’t have to know rnthe physics or the causal aspects of how something works, you just rnbasically follow somebody’s actions, do that yourself, and then you can rnpass on these kinds of cultures to the next generation. 
So inrn some sense, the fact that chimpanzees don’t rely on social information rnas much as they seem to rely on physics actually means they might not rnlearn about technologies in the same fast way that humans do.  Because rnif you think about the kinds of technologies that we deal with, you rnknow, they’re often so physically complex that we can’t explain them.  rnYou know, I use my iPhone every day, but I have no idea how it works.  rnYou know, I slide the little bar and that’s what I understand.  But for rnchimpanzees, all of the technologies they work have physics that are rnreally obvious or affordances that they can see that anyone can see.  rnSomehow actually paying attention to social information more than rnphysics might have allowed us to go beyond the kind of obvious way that rnthings worked to new kinds of technologies.

Recorded May 21, 2010
Interviewed by Andrew Dermont