IRA FLATOW, host:

You're listening to TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow. A bit later in the hour we'll talk about avian flu and Pluto's new moon, but first two new studies out in today's issue of the Journal Science look at the behavior of chimps when they cooperate or when they don't. Now, you know, people help each other. We all help others, even though we don't personally gain anything sometimes by doing so.

Well, you give, or you open a door for someone carrying a package, so why not our closest cousins the chimps? Well, perhaps that's what scientists of the Max Planck Institute were worrying about when they tested chimps against human toddlers to see if they would help a human adult struggling with a task. That was one study.

There was another study in which the researchers wanted to know whether chimps would cooperate with other chimps to get a food reward, and if they would purposely pick partners who were better at the task, you know, find a chimp that works better with getting that award. Joining me now to talk about cooperation behaviors in chimps, and perhaps ourselves, is Joan Silk, a professor of anthropology at the University of California, Los Angeles, and currently on sabbatical in the department of zoology at Cambridge. Well, lucky you, being in Cambridge.

Professor JOAN SILK (Anthropology, University of California, Los Angeles): Absolutely.

FLATOW: Tell us about the, uh, these two studies. They looked at different aspects of cooperation, correct?

Professor SILK: They did. They did. We make a distinction between cooperation which involves a cost to the actor and a benefit to recipient, and cooperation in which both parties benefit. So, the study which asked whether or not human infants and young chimps would provide help to adults was a study about cooperation in which only the recipient benefits.

FLATOW: Mm-hmm.

Professor SILK: And the other study, as you said, involves benefits to both of the animals.

FLATOW: Mm-hmm.

Professor SILK: And so the first study's interesting because very, very young infants and young chimps appear to be able to figure out what needs to be done, and they also seem to be willing to do it. You need to do, you need to know what needs to be done, and you need to be willing to do it to perform behaviors that are altruistic in that way.

FLATOW: Let's talk a bit about exactly what happened in that study, because that's really very interesting. You had 18-month-old human infants and chimps doing some simple tasks, and tell us how, where the cooperation, what the task was.

Professor SILK: So, the children were confronted with a situation in which an adult was trying to do something. They were trying to stack a book or they're trying to reach a marker that rolled out of reach, and the children watched this event. They weren't told to watch. They weren't asked to help. They weren't really instructed in any way. But on most of the tasks, most of the children, most of the time, completed the task. They provided a form of help. They picked up the marker, they tried to stack the book, whatever. So, the children seemed to understand that what the adult was trying to do, and then they tried to help them do it. The infant chimps weren't quite as adept as the human infants, so they didn't help on all the tasks, but there were some tasks, particularly tasks that involved reaching, in which the chimps did reach for objects and hand them to the human trainer.

FLATOW: Mm-hmm. I found it fascinating that even the human, the human toddlers could know what was going on, and feel altruistic at that point in their lives.

Professor SILK: Yeah, they're really young, they're really young. I do think that it's a little hard to know exactly what the kids were thinking, or what the chimps were thinking, so I read this paper and I was thinking about, and I remembered an event in, where my son was about five, he was just in kindergarten, and I taught him to set the table. I made a little diagram. We put the fork there, we put the knife there, a spoon there. He learned to set the table, he thought it was just terrific. He was really proud of himself, he would show people that he could do it, everything was great. So then after a small amount of time, I said, well, maybe you should set the table every night before dinner. Immediately, he said, you treat me like a slave. He was outraged. So, obviously it had been a game, and now it was a chore, and his attitude was really different.

FLATOW: Mm-hmm.

Professor SILK: So I think we don't yet know what's motivating the children to do what they do. It may be that they really want to help the other person. It may be more complicated.

FLATOW: There was an interesting aspect of that study, too, where if the testers threw something rather than drop it and look around for help...

Professor SILK: Right.

FLATOW: The babies, the toddlers knew the difference. They didn't feel like they had to go help out in that situation.

Professor SILK: Right, right. That's the control condition, and the control condition was to create a situation in which a very similar event occurred, but the context was different. So, the context in that situation, in the control condition, the adult didn't need any help, and the children seemed to figure that out...

FLATOW: That was...

Professor SILK: And I think that was quite remarkable.

FLATOW: That is remarkable. Let's talk about the second study where the chimps needed to recruit other chimps to help them reach for food on a platform.

Professor SILK: Yeah. I think this is a great study. So, there's a platform and there are two ropes, and in order to pull the platform close enough that the chimps can reach the food that's on the platform, both chimps have to pull on the rope at the same time. If only one of them pulls on the rope, the rope comes unthreaded, no food. So, this is a situation in which the chimps are very motivated to work together because they really like food and that's the only way that they can get it. But now they're paired with different partners, and they can choose between partners.

And the really lovely thing about this experiment is that when the chimps were first introduced to these two partners who are their, what I like to call, their assistants, so these assistants at the beginning, the chimps didn't distinguish between them. They would pick either one with equal frequency. But it turned out one of these assistants wasn't very effective. He didn't pull the rope at the right time, things just didn't go well when they worked with him. So, over time, the chimps began to prefer the other one, the other assistant, the one who actually was effective. And so this is, it's very clever, it's not, you know, it's, for us it doesn't seem that surprising.

FLATOW: Right.

Professor SILK: But nobody's ever demonstrated that chimps discriminate among their partners based on their effectiveness. So, this is an important result. It suggests that chimps are pretty sophisticated in collaboration in these activities that require joint action.

FLATOW: Mm-hmm. Well, what can you actually learn from these lab studies that you can't by studying these chimps in the wild?

FLATOW: Well, that's a good question because ultimately we're interested in what chimps do in the wild. We're not real interested in what chimps do in laboratories by itself.

FLATOW: Mm-hmm.

Professor SILK: So, the problem about studying chimps in the wild is that it's hard to figure out exactly why they're doing what they're doing, and it's hard to work out what's influencing their behavior. So, in the wild, you might see, for example, that two chimps like often share food together. That may be, or let's say two chimps hunt together, chimps hunt and eat meat, they quite like to eat meat. So, two chimps might hunt together. Now, they might hung together because they're relatives. They might hunt together because they have a long- term reciprocal relationship. Or they might hunt together because they figured out that they're particularly effective when they work together.

Just watching hunting in the wild, you can never figure this out, you could never distinguish between these possibilities. So we designed this experiment in the lab so that we can keep things a little bit more simple than they are in the real world. And we hope that by doing the experiments, we can then go back out to the field and think a little more clearly about what they might be doing.

FLATOW: Is this, are these kinds of experiments designed to just test the intelligence of chimps, or is it to test or to understand something about ourselves from this?

Ms. SILK: I think different people are interested in different aspects of this. I think these two studies were both done by people who are interested in figuring out how humans are similar to other primates and how they're different. And I think both of these things are very important. In the case of humans, we're one of the most cooperative animals on the planet. We regularly interact with people that we don't know, with people that we won't meet again, and we're often willing to provide help to them. That makes us, as we say in my family, very funny monkeys, because most of other primates, restrict cooperation to their relatives or to reciprocating partners.

FLATOW: Hmm.

Ms. SILK: But always to animals that they know well and that they have a chance to interact with again. So, you know, helping a stranger, you know, holding open a door for a stranger in the supermarket is not something that we'd expect to see in chimps.

FLATOW: But we only have a minute left but, you know, hearing researchers talk about chimps and other primates, you hear a wholly different story about the bonobos.

Ms. SILK: Ah, bonobos.

FLATOW: Do you think if you studied the bonobos you might find more, even more cooperation. We keep hearing about how they react so differently than chimps do.

Ms. SILK: Well, I think we might, it's really intriguing. I'm pretty firmly wedded to data, so for me, I got to see the data before, before I'll know. But it'd be great to do these kinds of experiments with bonobos, but bonobos are scarcer than chimps so it's hard to get access to them.

FLATOW: Yeah.

Ms. SILK: But it'd be really interesting.

FLATOW: Well, that's what were all here for. Really interesting stuff. Thank you Dr. Silk for taking time to talk with us.

MS. SILK: Mm hmmm.

FLATOW: Joan Silk is a Professor of Anthropology at the University of California in Los Angeles.

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