The BBC website has more information about other animals and laughter studies.

http://www.bbc.co.uk/news/science-environment-15880045

I think the only feature that will prove to be truly unique to humans is the incessant (and pathetic) need to identify a feature that we share with no other creature. Guess what, we're animals! Let's get over ourselves.

This show was awesome!

To those concerned about the rat being aggressively treated: I worked in a lab in undergrad where we studied aggression in rats. They have a couple distinct defensive and aggressive postures, none of which expose the rat's stomach. The professor seemed to be putting minimal pressure on the rat's abdomen as well.

After I left the job, the lab studied the sounds baby rats make, using equipment similar to that used by Dr. Panksepp. The baby rats make a screaming sound when they are hurt or hungry and it sounds nothing like the sounds made by the rat in this episode.

That rat was having a blast! Thinking about their lab serving as a rat playground and tickle emporium makes me happy.

I laugh occasionally when I'm alone. In fact, I recently woke up laughing from a dream in which I thought of something funny. I don't remember now what it was, of course, but I'm pretty sure there was no pseudo-social aspect. I also don't think there's a pseudo-social aspect when I laugh at a funny video of talking cats on YouTube.

Another aspect of the sociality of laughing that was not addressed was it's likely basis in a type of shame/shame-avoidance response; shame being a vital social emotion. Laughter often emerges after mild to moderately embarrassing scenarios to subdue the sense of unwanted or uncomfortable exposure or norm violation in social settings. Regarding cocktail parties with lots of laughs but few jokes (a point that was made in the piece by Dr. Provine) laughter helps to "smooth" interactions in which we are also compulsively self-conscious.
(hee hee har har)

I honestly laugh alone all the time, but it's definitely not normal. I don't think.

It seems like the rat in the video was being played with very aggressively. I don't doubt that the rat was enjoying it as play, seeing how it bounced around just a little bit at the end. It's always pretty clear if a rat wants to play & if it is enjoying playing by watching its behavior, because a happy rat hops a little and makes motions to solicit you to play more.

I do doubt that the sounds you hear are laughter, though. How do you know the rat isn't just making "enough,enough" noises? Granted, an unhappy rat normally squeaks in the audible human range, but I suppose I'm a bit skeptical. I think having footage & audio of several rats playing might help.

I was a bit taken aback the vigorousness of the "tickling" too. But I guess if the rat isn't biting, it can't be too unpleasant for it.

On the aggression of laughter, I've said for a long time now "humor isn't funny". What I mean is, most jokes, and things that make us laugh, are at the expense of others. The misfortunes, shock, pratfalls, humiliation, and stupidity of others is the basis of most humor. The laughter from such is mostly of a "there, but for the grace of God, go I", and "it's funny 'cause that person's dumber than me".

And how much of laughter is a nervous reaction? You seen people who laugh, seemingly, inappropriately.

Oh my god, I love that Mephistopheles' laugh from "Faust" is included in this story. It was my favorite part of French class from senior year.

I'm not surprised that rats or other animals laugh. At a fairly incredible rate, scientists are confirming what many of us knew intuitively all along: Animals have rich and diverse emotional lives.

Some of my cat's games with me remind me of a human baby's first games: Scenarios that are just a little bit dangerous, but not really. Is that not elementary humor?

We're discovering all these abilities in animals. They have a broad spectrum of interests and ways in which they experience life. When will we start treating them better? For example, when will we stop creating billions of them each year just to kill them? Why aren't rats included in the meager protections of the Animal Welfare Act? Why do we treat complex sentient individuals as disposable commodities? Is it "might makes right?" If we haven't learned to treat animals with kindness and respect, what have we really learned?

My dog certainly doesn't laugh, but I have no doubt that (a) she has a rich sense of humor, as do many other dogs, and (b) she interprets my laughter as a good, happy thing. She deliberately does things to get my attention, and if her antics make me start laughing, she knows she's getting somewhere, and her eyes twinkle and her tongue lolls and her tail wags, and it winds up being a feedback loop, where she acts goofier and I laugh harder. Obviously, people can debate what's going on in her head, but to me, who has known her for six years, it's obvious she's sharing in the joke.

http://sciencenow.sciencemag.org/cgi/content/full/2008/403/4

Maybe this segment is on Radiolab's cutting room floor but I would have liked to have heard more about aggression.

There was some acknowledgement of the aggressive character of much laughter, but I think it could have been explored further. If I remember right, there is some research on the social meaning of the rictus (grin) in higher primates that connects "smiling" with territoriality and physical aggression. This has some sociobiological implications for the relentless and often vicious ad hominem jokes in Greek Old Comedy (think Aristophanes) and in related phenomena both in and outside of the Greek world.

Chuck

If laughing is social, would a child raised in a home where it is never exposed to laughter (neither through human contact or outside stimuli) know how to laugh, when to laugh or understand laughter? Also, if pitch in laughter has evolved to communicate something, what pitch is understood to be diabolical or maniacal laughter? I found the laugh-box laughter in the last segment disturbing, not funny. Once I saw my husband laugh at it though, I was eventually crying I was laughing so hard.

The Elaine May and Mike Nichols segment made me wonder: Do you guys have a collection of Radio Lab outtakes stored away somewhere? That could be a fun listen. The show is produced in such a way that it seems like just a casual one-take conversation, but I'm guessing that there may be some studio wizardry going on and that sometimes things break down in laughter etc.?

I love to laugh and this show really helped. Thanks... more on laughing please. And.... have you tickled your rat today?

Julie Wolf - Seattle

I miss terry gross - this show is not for me.

I mean HEAR...doh!

Went home and got my son's pet rat out. Tickled her....because it looked like maybe the one the video was being jerked around too much. But turns out there is no gentle way to tickle a rat. Believe me I tried. But she did seem to love it. Made little noises that I could here. Don't know about ones I couldn't. She did keep following my hand around after that too. But then again she has always been a attention seeker.

If laughing relieves stress in humans, would it do the same for animals? This is why I love this show. It makes me ask more questions and raises discussion. Thank you! I can't wait for more.

Wonderful to have you both back! Great show!

LOL!!!!!!!!!!

Anne

This is perfect:
http://www.unitedmedia.com/comics/dilbert/archive/images/dilbert2008149680305.gif

I joked all throughout my last interview. I guess I was tying to 'get in the head' of the interviewers. Still waiting to hear if my magic worked...

Off topic, but it resonated with me when Robert chastised Jad for using the word "Awesome." I'm going to be 31 tomorrow, and I still use "Awesome." And I'm embarrassed about it. But, sorry Robert, "delightful" just doesn't cut it.

In any case, awesome episode, guys.

It seems to me there could be another interpretation of what's going on in this video. I was struck by how vigorously Dr. Panksepp handled the rat, and that, if looked at from the rat's perspective, this might seem more like an attack by a predator than a tickling session. Looked to me like the rat was trying to kick and defend himself, and the sounds quite possibly could be shouts of anger and warning.

Great to have the show back!

Essential listening in terms of infectious laughter: The Laughing Policeman by Charles Jolly in 1922

http://www.youtube.com/watch?v=iZPkrkT6BVQ

Hey, I thought you said there would be a video of rat tickling. I am as wary as Michal above, is that true laughter, or just friction?

Not to be cynical or anything, but is it possible Dr. Panksepp is just shaking little bits of air out of the rat when it's tickled? Or is that the subsonic sound of a persons bones rubbing together or flesh rubbing against fur? I would be interested to read the full articles.

I have cared for many foster babies. Each of them was different as to when they laughed for the first time. One was a month old, another two, some not till three months. It is always a different and distinct milestone that we watch for a write down in their memory book.

I like to add few things here:Excellent show and I enjoyed it

I am a pediatrician for about 20 yrs.
Baby attains the first developmental milestone called social smile at about 6 (40-42days)weeks.This becomes a coo and then becomes a distinct laughter about 80-90days.Though some babies are outliers to this timeline,Amanda, Aristotile are very correct in their observation.
There is one type of seizure called gelastic seizures where the child laughs uncontrollably for with no stimulus and I had one such child.

When will these be posted for listening?

Just a few things.. I'm listening to the show right now and I remembered seeing a program on television many years ago where a baby gorilla in San Diego zoo is tickled, and laughs!
Also, a comment about the possibility birds singing when they're 'happy' (assuming they can have such emotions) reminded me of coffee shops in Singapore where songbird enthusiasts bring along their caged birds, hang the cages up, and listen to the birds singing with each other for hours and hours.