A conversation with the professor of psychology at Yale University.

Laurie Santos:  My name is Laurie Santos and I’m a Professor of Psychology at Yale University.

Question: What primates do you work with, and what’s your methodology in working with them?

Laurie Santos: Yeah.  So I study primates because I’m interested in humans.  I want to know what makes humans tick but if you’re really interested in that question, it’s kind of actually kind of bad to study humans because they have too much stuff.  You have too much education and culture and all that stuff, so we study primates to kind of strip away all that other stuff and actually look at humans in their more ancestral state, try to get our evolutionary origins.  We study a group of Capuchin monkeys on Yale Campus that we have in kind of a big zoo enclosure and that kind of lets us get up close and personal with this group of monkeys.  Capuchins are really a cool group of monkeys to work with because their new world monkeys so they’re really distantly related to us but they are really similar to us in lots of ways.  So they’re very good at using tools, really complex social relationships, they’re just a great model for studying humans.

We also work with a group of primates down at a field site in Kyo Santiago, Puerto Rico.  It’s this great tropical island right off the coast of Puerto Rico and its home to about a thousand free-ranging monkeys so this is a wonderful facility because the monkeys range free.  You know they’re really in a naturalistic setting but we kind of go down there and really study them out there in this awesome setting.

Question: What special challenges arise in working with capuchin monkeys?

Laurie Santos:  Yeah, so capuchin monkeys are great and sometimes difficult to work with in part because they’re so smart.  The monkeys we have at Yale we’ve named after characters in James Bond movies, and those names are especially apt because they are quite smart, but that means that a lot of times they’re outsmarting me and my students, you know, breaking out ****, stealing things that they’re not supposed to have so it’s fun, but they’re really smart but it’s also kind of challenging that they’re clever, sometimes more clever than we are. 

Question: Why does your research compare adult apes and human babies?

Laurie Santos:  Yeah, the reason a lot of primate researchers actually compare their primate subjects, not with adult humans, but with infant humans, is for the following reason, and that’s just that one reason to study primates is there a great model for humans minus all kinds of human-specific experiences, you know, so they don’t have teaching, they don’t have kind of language and that sort of communication system.  They also don’t have all the kind of technology stuff that we have, iPhones and that sort of thing, and they never will.  Human beings are an interesting contrast to that because they lack at least experience with a lot of that stuff.  They’re too little to have those experiences, but they have a brain and a mind that’s set up to eventually get them, so most six-month-old human infants don’t know how iPhones work, you know, they haven’t had much in the way of you know the typical Western education system, but their probably going to get it or at least they have the capacity to get it.

So comparing infants and primates actually lets you say, okay, here we have a mind that eventually going to get this stuff it hasn’t had yet, and here’s a mind that might never get it, what are some of the similarities we see and what are some of the differences?

Question: At what point does a human baby’s mental capacity outpace that of the smartest ape?

Laurie Santos:  Well, if you’re looking for where, when humans can developmentally beat out you know the best non-human animal; I think you know it’s a very human-centric kind of question right, we’re thinking about you could ask for each particular ability, you could say oh when for our Theory of mind do we kind of out-pace apes and so on but for general abilities, I mean I’ll never be able to swing from the canopy rain forest the way that a Capuchin monkey does.  You know, and if you go beyond primates, I’ll  never be able to echolocate like a bat, so to a biologist even that question might seem like, well, for the stuff we do, great, but you know there’s a lot of things we can’t do that you know other species can so, so it’s a tough kind of comparison of, you know, when do we kind of overtake them in the graph.

Question: What has your research revealed about primate “theory of mind”? 

Laurie Santos:  Yeah, so one of the things we’re interested in studying the monkeys for is because we want to see do they have the kinds of cognitive capacities that we have as humans that we’re really proud of, and one of these things is what we call a theory of mind.  It’s complicated term but what it really just means is the fact that we look out in the world and watch human behavior; we don’t see just behavior, we see all these things going on inside the head so we see other people’s beliefs, their intentions, their desires, that’s how we kind of make sense of the world.  It’s a hard problem from a psychology perspective because we can’t see any of that stuff directly.  We’re making all these kind of crazy inferences about what’s going on in other’s heads.  So lots of researches have wondered do other animals do this.  Can they go beyond what they see and actually infer other things?  The way we’ve tried to get at this is a little bit tricky.  We’ve said, well, what are the contacts in which other species might use a theory of mind of they had them, and the sad thing is that if you think about evolution, usually the way other species might use a theory of mind is actually to outcompete others, to deceive others, to do kind of slightly dastardly things with of what they know about others beliefs and intentions.  So we set up a big series of studies at the field sight to actually see the monkeys know when it’s a good time to deceive us.  In other words, do they pay attention to what we can and what we know?  So the experiment’s pretty simple, we set up a human who has some treat that the monkeys might like, like a piece of grape, and we just vary whether the human can see the grape, and so he’s either facing or he’s turned around and there’s a barrier in front of his face, and what we do is just ask, you know, does a monkey subject try to steal it?  And what we find is, surprisingly, the monkeys use pretty much the same cues that humans use to decide when somebody can see them, so they don’t steal a grape if somebody’s facing forward, but they do if somebody’s turned to the side or looking away, so they’re very good cheats and thieves, but in showing that they’re good cheats and thieves we’ve actually been able to see they have some aspects of our own theory of mind.

Question: Are there any features of human cognition or behavior that have zero primate equivalent?

Laurie Santos:  Yeah one of the things that, the question of what’s uniquely human is actually a big one and you, depending on who you ask you might get really different answers.  If I had to put my money on something that was actually uniquely human, it seems in some funny way to be our motivation to actually interact with others, in a funny way.  And what I mean by this is that generally if you look at any humans anywhere, if they’re hanging out with other humans they’re often doing something where they’re showing something to another individual.  So you see something cool and you say, “Oh hey, look at this cool thing.”  And to psychologists this is a process of reference, right, so sharing, referring to information out there in a world and it seems like other primates even though you think this is kind of a simple ability, they seem to lack at least the motivation to do this.  This leads to the fact that they don’t have the kind of communication that we have with things like language with nouns that can kind of point to things out there in the world.  They also don’t seem to share their own desires and intentions with others, which leads to a lack of kind of cooperation in a lot of domains, so if I had to put my money on what was uniquely human I’d go with the kind of motivation to share information with others.

Question: What has your research revealed about monkey and human economic reasoning?

Laurie Santos:  Yeah so a lot of the work with primates actually tries to explore all these aspects of human cognition that we’re in some sense most proud of.  You know, things like a theory of mind and so on.  But less work is actually focused on some of these processes that are just universal in humans but are kind of dumb and in some ways really systematically dumb.  So we took up the charge of saying well you know are any of these dumb biases shared with other primates.  And we started in the economic domain, in part because this is really a spot where humans can be bad and the fact that we’re bad can have really enormous consequences such as the current financial collapse and so on.  But to do this, to sort of study this question you know do monkeys share our economic biases we had a bit of a challenge because of course our monkeys don’t actually use money yet.  So the first task was actually to introduce a new currency to our monkeys.  We did this by giving them little metal washers and teaching them that they could trade with human experimenters for food and the amazing thing was that they actually picked this up really quickly so the monkeys got really flexible with this and we just then put them in a market.  So they get a little wallet of tokens in the morning and they got to go into their enclosure and they had a choice of different experimenters who sold different foods at different prices and we just said you know, “How do they do?”  “How do they compare to humans?” And what we found was really striking because in the spots where humans are very rational, where they obey all of the economist’s models, the monkey did the same.  So when different goods go on sale so if apples go on sale today the monkeys would buy more apples.  And they do it in a way that all the economic math would predict almost perfectly, almost amazingly even though they had you know pretty much no experience with the market.  The other striking thing was that the monkeys seemed to show exactly the same biases that humans show and one of the important ones is what’s often called Loss Aversion.  Basically,  this is the idea that we don’t like losing things and we get more emotional about losing things that we get happy about gaining things and this can actually lead to a bunch of biases that play out in real markets.  Like the fact that many people would be better off selling their home  at a slight loss than holding on to it while the market kind of careens downward and so on.  So our Loss Aversion plays out in all these ways we said you know are the monkeys loss averse?  And the way we looked at this was to present the monkeys with a choice between traders; one trader gave a piece of apple as promised, so he showed the monkey a piece of apple, and then when the monkey paid him he got that piece of apple.  The other experimenter always showed the monkey two pieces of apple but when the monkey paid that experimenter, the experimenter only got one.  And the idea was does the monkey take into account what they think they’re going to get or do they just care as they probably should in what they get overall?  And we found is that the monkeys reliably avoid the guy that gives them less than what they expect.  It seems like they too might be averse to losses, averse to these situations that seem like their losing out even though it doesn’t actually affect how much food their getting overall.  The cool thing about all of this is it suggests that many of these biases that play out in the financial crisis might actually be shared with capuchin monkeys, which means they might actually be thirty-five million years old.

Recorded on January 26, 2010
Interviewed by Austin Allen