Archive for October, 2012

Roller coasters

Roller coasters fill me with dread, until they actually start moving. Source:

I kind of like roller coasters.  I don’t love roller coasters in the way that some people do, and there are certain roller coasters I simply won’t go on, such as wooden roller coasters, mostly because they don’t strap you into those types of coasters with hydraulics.  I want that big harness to lock down kind of painfully over my shoulders, and I even pull them down tighter onto my shoulders than is necessary.  And, every single time, I feel a moment of intense panic, because I have been asking myself, all the way through the line, and even as the workers are giving each other the thumbs up signal that will send us on our way, “What if my harness isn’t really locked?”  Of course, it always is, and the car takes off.  But I like them well enough that I can often work up the nerve to ride on them, even if they make me nervous.  That’s part of the fun, right?

Here is here the odd behavior comes in.  The minute the car leaves the starting area, I start laughing.  And I don’t stop until we get to the end.  And it isn’t just a little chuckle.  Oh no, it’s a loud, braying laugh that shakes my whole body and makes the muscles of my stomach ache.  It’s been so obnoxious that sometimes, as we’re climbing that first big steep hill that starts all these coasters off, people have actually twisted around in their seat to give me dirty looks.

What on earth is going on ?  Why am I behaving this way?

Well, in the 70s, Solomon proposed an explanation for this behavior, which he dubbed the Opponent-Process Theory.  There are several different version of the Opponent-Process Theory, each of which addresses different things, such as color vision (which we are familiar with from the lecture on vision) to motivation. Solomon’s theory dealt specifically with emotional responses, and is outlined briefly in the video below, plus I’ll describe it as well.


 So, what Solomon proposed is that every emotional response is biphasic.  In other words, there’s an initial emotional response, which they call the a process, that is experienced.  This a process is followed by the opposite response, the b process.  As the video shows, a person making their first skydive will feel increasing nervousness as the moment of the jump approaches.  Successful completion of the jump produces a state akin to euphoria, which is the opposite of the initial extreme trepidation.

This is a slide from one of my Learning lectures that shows how the two emotions work (on the left) and what is experienced emotionally (on the right).

This is pretty much exactly what happens to me when I ride roller coasters.  I’m horribly nervous standing in line and actually getting into the harness, almost to the point where I feel like I’m going to faint.  As soon as the car gets going, however, the opposite response kicks in.  For most people, it would be after the ride is over.  For me, the worst part is over as soon as the car takes off and I feel safe knowing I’m not going to get flung from the car due to a faulty harness.  So I start laughing.

Obviously, my nervous system is controlling this behavior, and I have to wonder about the exact sequencing of the emotional responses that are experienced.  I think it’s safe to assume my “fight or flight” response, controlled by the sympathetic nervous system, is activated while I’m standing in line.  I feel all the classic symptoms of extreme nervousness.  Nothing new or interesting there—these rides are supposed to make us feel that way (because the designers knew full well about the b process, I think).  The curiosity here is the opposite response.  Why don’t I just go back to my more neutral emotional state after the ride starts?  Why do I have such an extreme response in the opposite direction?

One thing that’s true about our body is that it generally likes to maintain a regulated state.  You’ve heard the word “homeostasis,” which means “steady state” before.  Our body likes to maintain a balanced state of affairs physiologically, neither too hot nor too cold, neither too full nor too hungry, etc.  The same is true of our behaviors as well, including our emotions.  The whole point of the biphasic emotional response is to get back to equilibrium, and perhaps the only way to manage that is for the body to overshoot in the opposite direction after a particularly strong emotion is felt.  So, we feel extreme fear, and to counter that, we feel extreme happiness.  That’s kind of the good way for things to go because we’re left feeling generally more positive even when we get back down to the relatively neutral state.  The bad part is when the initial feeling is extreme happiness, because that’s countered by extreme sadness for a little bit before we recover.  But all of that is necessary to get us back to that even-keel we like to maintain.

I like to think, when I ride roller coasters, that I am laughing in the face of adversity.  However, the truth is, I’m really just laughing in relief!

Several years ago, a study by Ross, Owren, and Zimmerman (2009) made quite a splash.  Prominent scientists, including Jerry Coyne (who pens the excellent blog “Why Evolution is True”) wrote about it, and the study was even featured on news programs that appeared on the BBC.

The reason this particular study generated such interest is because it had long been hypothesized that laughter, some form of which is seen in most of the great ape species, was the result of evolution.  Many researchers, including Provine (1999) argued that laughter was likely present, probably in the form of some kind of panting behavior, in an ancestor common to all extant humans and great ape species.  It’s an idea that makes a great deal of sense.  We have known for a long time that chimpanzees will make a panting sound when tickled that sounds curiously like laughter.  Darwin even describes this behavior in his book on emotional expression (Darwin, 1872).  Orang utans and gorillas do the same.

So here is what Ross and her colleagues did to show that the behavior of laughter is similar across species of great apes, and it is quite stunning in its simplicity.

They tickled a lot of animals.

I mean, imagine yourself as a research assistant in this lab, and your boss comes and tells you that your job is going to be to tickle a bunch of infant great apes!  That sounds like the best job in the world to me.  Specifically, their job was to tickle 21 infant and juvenile chimps, bonobos, gorillas, and orang utans, and three infant humans.  And while they were tickling them, they recorded the sounds they made and subjected them to an analysis.

So, what did they find?

From Ross, et al (2009). This is the tree they constructed by comparing the laughs of several primate species.

As expected, they found some similarities in the acoustical structure of the laughter produced by the species under investigation. Using those similarities, they placed the species into a tree arrangement, which looks like this:

To construct this image, they analyzed the auditory profiles of the laughter from their test subjects.  Essentially, they found the greatest similarity in the auditory structure of laughter between bonobos and chimpanzees.  This is hardly surprising, since those two species are very, very closely related.  Their laughter was structurally similar to humans.  The other two great ape species, gorillas and orang utans, had laughter that was the least similar to human laughter (though it was still fairly close).

What is extraordinary about this particular chart is that it bears a striking resemblance to this:

This is the taxonomic tree for great apes.  In other words, Ross’s, et al (2009) laughter map matches the tree that is produced by analyzing the DNA of all these species, a genetic family tree, if you will, of the hominids.  It is important to note that none of the non-human species have a vocal apparatus that is capable of producing human-like speech, though there are structural similarities in the throat and larynx.

So, why did laughter (tickle-induced laughter, at any rate) evolve?  Provine (1999) suggests that laughter is all about social bonding.  The young of most mammalian species engage in rough and tumble play, and tickling is often an important part of this play.  The tickling produces mutual laughter, accompanied by the release of neurotransmitters that induce positive affect, and the resulting enhanced social bonding is obvious.  This behavior carries over into adulthood and permeates many social encounters. Informal research from Provine’s (1999) laboratory indicate that people laugh the most often in social encounters, many of which do not necessarily include any humor.

I have said in class that the main function of the mammalian brain is to help us navigate the environment.  Some argue that the main function of the human brain is to solve social problems.  I think they are one and the same–the main things we need to navigate in our increasingly complex environment are social relationships of one kind or another.  Our livelihoods, by and large, revolve around successfully navigating relationships with our families, our friends, our teachers, our bosses, our neighbors, and even strangers we encounter in our everyday lives (I consider driving a highly social behavior, for example, even though it doesn’t appear to be that at first).

The other thing that the Ross, et al (2009) study makes quite clear is that laughter in great apes is a distinct and clear behavior that likely serves some purpose (probably social bonding).  In other words, we are not anthropomorphizing the behavior when we hear it.  It really does seem to be laughter in the way we, as humans, understand it.  Though we can never know exactly what a non-human animals is experiencing, we can correlate the behavior that occurs with the laughter.

I want to close out this blog entry with a personal story.  I did quite a lot of research with my mentor at the Smithsonian’s National Zoological Park, in Washington, D.C.  They have several orang utans there, and my mentor was engaged in a research project with them.  The experiments we were doing, which were to look at the cognitive capabilities of the orangs, used touch screens so the orangs could make their responses.  When we were first starting out the project, we had to do a lot of troubleshooting.  This usually involved wheeling the apparatus up, putting a very obvious picture up, such as a big, red leaf, and trying to figure out ways to get the orangs to reach out through the mesh of their habitat to touch the apparatus.  This wasn’t such a problem with the females, since they have smaller hands and could just reach out.  There were other problems with the females, since the first time we rolled the apparatus up to one, named Bonnie, she reached out and punched the apparatus so hard she broke it.

This isn’t Junior, but I wanted to show you what their big, banana-fingers look like. The original picture appears at

The real problem turned out to be the male, Junior.  Male orang utans have very large hands, and these enormous, banana shaped fingers.  We though if we put the apparatus up close enough, Junior could poke his fingers out and make his responses.  So we started training that.  My advisor would often stand near the apparatus, and occasionally would reach in and try to guide his fingers to the stimulus to touch it.  After a few trials of this, he started moving her fingers around whenever she reached in, rather than letting her move his fingers.  We knew he was perfectly capable of touching the screen on his own, so we couldn’t figure out what he was doing until we let him just move her hand around, and he used her hand to touch the stimulus.

At this point, he sat back on his haunches, and started that odd panting laughter that they do.  It was clear to us that he thought this was hilarious.  Of course, once we realized what he was doing, and the fact that he was laughing over it, it made us laugh, too.  Aside from being a great story, his behavior also raises a tantalizing question about a sense of humor in species other than humans.  We know we have it, though humor is highly subjective, and highly complex in terms of behavior.  It’s incredibly difficult to understand what humor is to another species, though I think we got a very clear glimpse of it in the male orang we worked with.

There was a lot of laughter on that research project–orangs are really a joy to work with.


Darwin, C. (1872). The expression of emotion in man and animals. London: John Murray.

Provine, R. (1999). A Big Mystery: Why Do We Laugh? Retrieved 10/9/2012

Ross, M.D., Owren, M.J., and Zimmermann, E. (2009). Reconstructing the evolution of laughter in great apes and humans.  Current Biology, 19, 1106-1111 doi: 10.1016/j.cub.2009.05.028