Tickling Primates To Learn About Laughter Do nonhuman primates have a sense of humor? Marina Davilla Ross and colleagues tickled baby gorillas, chimps, orangutans, bonobos and humans. Publishing in Current Biology, the researchers analyzed the sounds the primates made, looking for clues to the evolution of laughter.
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Tickling Primates To Learn About Laughter

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Tickling Primates To Learn About Laughter

Tickling Primates To Learn About Laughter

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IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR News. I'm Ira Flatow.

A little bit later in the hour, Isaac Newton, crime fighter and fiscal revolutionary. We'll talk about that later. But first, can you name this sound?

(Soundbite of orangutan)

FLATOW: Let's hear that again.

(Soundbite of orangutan)

FLATOW: If you guessed that's the sound of an orangutan being tickled, you got it right. I don't know how you could have guessed that. But writing the journal Current Biology, a team of researchers describe a project in which they record sounds of different primates. They've got chimps and gorillas and Bonobos and even humans, human infants there, and they analyze the sounds and look for clues to the evolution of laughter.

That's what we are going to be talking about at the first part of the hour with my guest. Marina Davilla Ross who is a researcher in the Department of Psychology at the University of Portsmouth in the UK. She joins us by phone this evening. Welcome to the program.

Dr. MARINA DAVILLA ROSS (University of Portsmouth): Thank you, hello.

FLATOW: Hi there. Tell us, how do you go about collecting these sounds?

Dr. ROSS: Well, apes were being tickled in seven European zoos by their caretakers, and also I went to a rehabilitation center, where I had the chance to tickle the apes myself because I got to know the apes, that's an important part of tickling. And yeah, we collected then these vocalizations also from human infants who were tickled by their mothers, and measured these sounds and rebuilt the evolutionary relationship of these vocalizations.

FLATOW: And what did you discover?

Dr. ROSS: Well, the resulting evolutionary tree just based on acoustics coincided with what we know from genetic research. So we could conclude that these vocalizations all share a common ancestry. In other words, that great apes also can laugh.

FLATOW: Well, how do you they are laughing? I mean when you tickle them, you know, when I - you tickle me, I sort of know that - you know that I'm laughing. But how do you know that the ape isn't protesting or something?

Dr. ROSS: The ape is in protest?

FLATOW: Yeah, how do you know it's laughing? How do you know it's not protesting what you are doing and doing vocalization - don't do that again or something?

(Soundbite of laughter)

Dr. ROSS: Yes. A very important part of the tickling sessions was that the tickler and the tickee were enjoying themselves.

(Soundbite of laughter)

Dr. ROSS: So in other words the ape had the chance to leave but the ape usually did not leave. It was usually the tickler, the human tickler who wanted to stop…

FLATOW: I see.

Dr. ROSS: …doing it at one point of time.

FLATOW: Do they actually ask for more?

Dr. ROSS: Well, they sometimes, for instance, showed their foot. They wanted their foot to be tickled. Others turned around for the next to be tickled and, you know, often they engaged into play within the tickling sessions.

FLATOW: Do apes tickle each other?

Dr. ROSS: Yes. This is a very important part of their social play behavior.

FLATOW: So they tickle - and can you trace back through your analysis of the sounds that they make which - you know, the lineage of the apes? And how - you know, and the evolution and which were the older apes that match up with DNA?

Dr. ROSS: We did not do such an analysis because the evolutionary relationship of the species themselves is already quite well established. So we were interested in leaning on this very well established tree in order to learn more about these specific displays through our analysis. The analysis we conducted did not involve any genetic data.

FLATOW: I see. And how far can you trace back in the family tree of primates? And these - how far does laughter go back?

Dr. ROSS: Well, since we've measured all the four great ape species, the orangutans, gorillas, Bonobos and chimps, as well as humans, of course, we could state that laughter goes back as far as the last common ancestor of all these species, which lived approximately 10-16 million years ago. That's not to say that laughter doesn't go any further. It could be even older than that.

FLATOW: But you've got it down pretty well that you know so far - 10 to 16 million years ago.

Dr. ROSS: We know that it goes that far back, but it could be older.

FLATOW: And how far do you think you could trace it back?

Dr. ROSS: Well, we don't know.

FLATOW: Yeah.

Dr. ROSS: We studied just the great apes.

FLATOW: And there's no way to know what that first ape back 10 to 16 million years ago - what that laughter sounded like.

Dr. ROSS: Well, yes, because we - once we have had established a tree, we used the acoustic data to map the acoustics on this tree. And we found that it was likely that this last common ancestor of all these species was producing a laughter that had a very short laugh series.

FLATOW: Right.

Dr. ROSS: And within these laugh series, the single calls were more noisy.

FLATOW: I want to play the piece of tape we have of this orangutan for us again, and then I want you to analyze it, what you can tell from listening to it. So let me get ready to get that tape up to play it.

(Soundbite of orangutan)

FLATOW: Didn't sound like laughing to me, but…

Dr. ROSS: No, no.

(Soundbite of laughter)

Dr. ROSS: But it's not surprising because one is looking at evolutionary processes. For human laughter, it's quite a complex vocalization. When you think about how the very first laugh sound was probably sounding like, you would not expect it to sound like human laughter. You would expect it to sound more rudimentary than that. So one should also consider when measuring evolutionary processes to encounter evolutionary changes, which are likely to occur over many million years.

FLATOW: That's interesting. So laughter evolves just like the primates do, the sound of the laughter evolves.

Dr. ROSS: Yes. You would not expect an orangutan's laughter to sound like human laughter.

FLATOW: Do they have the vocal cords or whatever we use to laugh with that could make them sound human?

Dr. ROSS: Well, yes. All the great apes have these vocal folds.

FLATOW: Yeah. Let's go to the phones. Joanne in Phoenix. Hi, Joan.

JOAN (Caller): Hey, hi, Ira, how are you? And hi, Ms. Ross. How are you?

Dr. ROSS: Hi.

JOAN: I am so interested in this topic and one of the reasons why is because I recently edited a book dealing with the origins and the evolution of the species, both human species and animal species about laughter. And I'm just wondering if any of your research, Ms. Ross, has also incorporated why we laugh, both humans and animal.

Dr. ROSS: No. We measured the acoustics and we measured the evolutionary process of these sounds. So I cannot make much of a statement of the function of it. But when one looks at how laughter is being used in great apes, it's very closely linked to play behavior.

FLATOW: But would they…

Dr. ROSS: In humans, of course…

FLATOW: I'm sorry, go ahead.

(Soundbite of laughter)

Dr. ROSS: In humans, of course - we also produce mocking laughter. We produce laughter in various other contexts. So I think this is a very - it's very interesting that apes produce them more in these socio-positive interactions.

FLATOW: Thanks, Joan.

JOAN: Oh, you're welcome, Ira. Thank you. And if anyone's interested, that book is called "Why We Laugh."

FLATOW: "Why We Laugh." Thanks for calling. Are you saying that they will laugh at each other without being tickled if they see something funny?

Dr. ROSS: I have never observed apes produce laughter when they were watching other apes do something where they were not themselves involved with. They produce laughter in various forms of play, but they have to be involved in that play behavior.

FLATOW: You mean touching each other.

Dr. ROSS: Not necessarily touching each other. Play behavior can be, for instance, also tug of war, and there can be various forms of play behavior that do not involve touching, like chasing one another.

FLATOW: And they certainly like it because they were upset when you stopped, huh? How long could you go on tickling them, do you think?

Dr. ROSS: Well, it depends upon the individual, but it seemed like some of them could do that forever.

(Soundbite of laughter)

FLATOW: Did that surprise you?

Dr. ROSS: Well, once - well, at the beginning maybe, yes, because I thought, wow, they must want to stop at one point of time, but after, yeah, after a few tickling sessions, it was not surprising anymore.

FLATOW: Let me get a phone call in. Let's go to Steve in Palm Coast, Florida. Hi, Steve.

STEVE (Caller): Hi. Quick question, I'll take it off the air. Do - have any of the great apes, do they have any behavior similar to what we would know like stand-up or telling jokes or something other than tickling that would cause laughter?

Dr. ROSS: Yes, there are various forms of play behavior that can cause laughter. For instance, it could be that one ape is chasing another ape, and the chasee is laughing or the chaser is laughing, or sometimes they play with an object, and they are pulling - two apes can be pulling that object towards them, and they might be laughing in these contexts. Yes, but they need to be involved with the interaction to laugh.

FLATOW: Let me get a quick question in here. Let's go to Elizabeth in Birmingham. Hi, Elizabeth.

ELIZABETH (Caller): Hey. I just had a quick comment. The orangutan laughter to me sounded like snorting, and when I laugh, I snort sometimes. They actually don't seem that far apart to me.

FLATOW: Yeah, that's a good one.

Dr. ROSS: Yes, there have - there has been also a study done where they found that a lot of our human laughter is not always this melodic, ha-ha-ha kind of laughter. It sometimes sounds grunt-like and pant-like. It can be very different, yes.

FLATOW: Would the most primitive laughter then, going way back, would that be more like snorting because it's a simple thing?

Dr. ROSS: Yeah, more grunt-like.

FLATOW: And then so over the years, it would evolve into a more complex kind of laugh until you get what we have.

Dr. ROSS: Yeah, there's more structure then. There's more variability within the laugh series.

FLATOW: Wow, all right. Thank you very much for taking - for staying up late for us today, taking time to be with us.

Dr. ROSS: Thank you.

FLATOW: You're welcome. Marina Davilla Ross is a researcher in the department of psychology at the University of Portsmouth in the UK, talking about an article she wrote in the journal Current Biology about apes that laugh.

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