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Psycasm is the exploration of the world psychological. Every day phenomenon explained and manipulated to one's own advantage. Written by a slightly overambitious undergrad, Psycasm aims at exploring a whole range of social and cognitive processes in order to best understand how our minds, and those mechanisms that drive them, work.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

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Thursday, June 16, 2011

Laughter and humor have also been omitted from most general accounts of human evolution, taking a backseat to evolutionary divas like bipedalism, encephalization, language, and culture.

- Gervais & Wilson, 2005


Yup, it's going to be a post on Evo Psychology. 'Ohhh... pfft', some of you think. This post is on evo psych for two reasons; the first is that this topic is just fascinating - it's on the evolution of humour and laughter (and humour and laughter in general); and second, this is one of the best evo psych articles I've ever read, and an excellent example of what evo psychology is all about.

[Just FYI, I have written on the topic of Lolz before.]

[Additionally, this post will be broken down into more than one part to fit everything in. This first part is a summary of what we know, the second part will outline the evolutionary arguments.]

But why is this paper an excellent example of Evo Psych? Well, unlike things like vision or attraction or communication, laughter is a unique human quality (well, not quite; but the manner, extent and contexts in which we employ it is unique), and so provides an excellent topic to investigate with a human evolutionary framework. Second, this topic synthesises huge amounts of data on what we currently know about laughter from many different domains (social psych, positive psych, biological foundations, neuroscience) and constructs an evolutionary framework that incorporates all of it. Third, it brings together many converging lines of evolutionary evidence (archaeology, comparative studies, etc) to inform their evolutionary hypothesis. And finally, the authors freely admit and highlight the weaknesses of their position, and (crucially) provide a number of predictions inherent in their framework.

All of this, however, in due course. Let me summarize some of the cooler things within the paper.

1) We humans have two kinds of laughter. Duchenne Laughter (genuine laughter, or laughter automatically elected from a stimulus with certain emotional connotations) and Non-Duchenne Laughter (self-generated and typically without emotional content). Duh, you say, but what makes this cool is that these kinds of laughter operate via partially dissociable neural pathways. Laughter is laughter is laughter is not so.

Duchenne Laughter originates in subcortical regions and within the brainstem (i.e. phylogentically older brain structures), whereas Non-Duchenne Laughter operates out of the motor, premotor and (crucially) the prefrontal regions (i.e. much more recent structures; and while the motor regions are old the prefrontal regions allow for wilful control over motor functions, including the movement and control of the face). This has been revealed by some crazy-cool imaging studies, as well as some equally cool studies on facial paralysis: There are (among others) two kinds of a facial paralysis implicated with laughter - Emotional Facial Paralysis inhibits spontaneous (duchenne) laughter yet allows for controlled and wilful (non-duchenne) laughter; and Volitional Facial Paralysis which is exactly the opposite - allowing for spontaneous laughter, but preventing one's ability to 'fake' the behaviour.

An interesting point here, and one which some of you may have considered, is that it may appear that you don't tend to employ Non-Duchenne Laughter. However, that's probably not so. Non-Duchenne Laughter is used when you're nervous, when you're appeasing someone, when you're being polite and (potentially) when you're just trying to fit in. Now it may feel as though you lack control (I certainly know it does in me) but good arguments have been made that many of us learn to employ this non-duchenne action automatically, thus making it feel as though it's automatic. For instance, this particularly kind of laughter does not occur in relation to stimulus, but is often used at the beginning or end of sentences or points made by the speaker - it's a kind of punctuation or 'metacommunicator'. It can (and does) provide a way to interpret the preceding statement.... Hell, you can see it on twitter... Ever ended a sentence in 'LOL'?

With regard to some of the arguments that support the position that Non-Duchenne Laughter can be automatic, it has been found that people majorly under-report the extent to which they laugh during their normal lives. For instance, I work with someone who is a chonic giggler (not a technical term...). They will give a laugh after every interaction. In many ways it's a positive trait, in my opinion, but it does frequently remind me of Doctor Julius Hibbert.

2) Duchenne Laughter is genetically predisposed to develop. All infants do it, and it's one of the very first vocalizations they can produce. Having read a little further afield, a significant degree of variance in humour styles (see Episode 11 of Psychobabble Podcast) is accounted for by genetic factors (Vaselka, Schermer, Martin & Vernon, 2010). Though humour and laughter are qualitatively distinct, and humour in many ways is a 'softer' topic for enquiry, it does lend support to the position.

Having said this, Laughter (of both varieties) is greatly influenced by culture and learning. The most handy example of this is probably the laughter-at-a-funeral example - even if something funny does happen at a funeral one should inhibit the expression of laughter, and should try to avoid eliciting it in others. I have a vague feeling that there are places the celebrate at funerals, and where laughter is appropriate... but I have no experience or knowledge of such things.

3) Human laughter is most-likely derived from the primate 'play face', a relaxed, open-mouthed facial expression accompanied by pant-like vocalizations. Chimp 'laughter' is not particularly recognizable as laughter upon hearing, but the stimuli that elicit duchenne laughter in apes and human children overlaps significantly. Stimuli such as tickling, safe surprise, and importantly, play (frequently 'rough-and-tumble play') all elicit laughter. The reason it sounds different breaks down into two reasons. The first is we have different physiology, and second, human laughter has become 'ritualized'. What this means is that, over time, proto-laughter has become recognizable as modern laughter through a process that makes it clearer and more distinct.

In the process of ritualization, a signal changes in structure so that it is more prominent and unmistakable, and thus more readily perceptible (Eibl-Eibesfeldt 1989; Grammer and Eibl-Eibesfeldt 1990). This occurs through the  simplification of a signal via the addition of rhythmic repetition, an exaggerated amplitude, and stereotypic structure.
The releasing threshold of a signal is also lowered during ritualization. All of these changes occurred during the evolutionary transition from ape play panting to human laughter (Grammer and Eibl-Eibesfeldt 1990).

Cited in Gervais & Wilson, 2005

Why was it ritualized? To understand this we have to know what laughter is for, socially speaking. First off, people don't laugh much when they're alone. Yes, there are expectations, but we're thirty-times more likely to laugh in company than without. That's a big difference and it suggests very strongly that laughter serves social functions. Some have argued that laughter exists to encode information about the sender for a receiver, but others have criticized this for being too simplistic. The alternative is that Laughter may serve to induce congruent affect in others. We like people who laugh, we find it attractive (see the LOLz post), and - importantly - laughter is contagious and is related to group size. Furthermore, groups who laugh together are more cohesive and cooperative, laughter reduces the negative affect in individuals who are stressed, and improves the mood within individuals. There are other things laughter does for us (to us?), but it demonstrates the utility of laughter being highly distinct and recognizable (i.e. being ritualized). For instance, consider a time when you've heard someone yell or scream and you've had to pause and ask 'Was that pain or was that anger?', or potentially 'Was that fear or surprise?'. Often it is clear, particularly if we've other information at hand, but taken alone it may be confusing. I suspect there are very few instances when you've heard someone laugh and wondered what it actually meant.


...and so ends part one. This post blew out in size, and so to do justice to their arguments I will include them in the next post. Hopefully this post has outlined a few things you didn't know about laughter and put some of the key points in one accessible place. But the best part (in my opinion) is coming early next week.



Gervais M, & Wilson DS (2005). The evolution and functions of laughter and humor: a synthetic approach. The Quarterly review of biology, 80 (4), 395-430 PMID: 16519138

Veselka L, Schermer JA, Martin RA, & Vernon PA (2010). Laughter and resiliency: a behavioral genetic study of humor styles and mental toughness. Twin research and human genetics : the official journal of the International Society for Twin Studies, 13 (5), 442-9 PMID: 20874465

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Brian Krueger, PhD
Columbia University Medical Center
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Great post, I can't wait for the next installment

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Cheers. I'm enjoying all the dangerous experiments you're recruiting, FYI.


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I am waiting for the next posts for your convincing arguments that this is not a just-so story. The problem as always it the fact that we don't have other hominid species to compare. And this bring us so many bad evo-psych papers, as you mentioned.

And just for fun:

Miracles are a unique divine quality (well, not quite; but the manner, extent and contexts in which the divinity employ it is unique), and so provides and excellent topic to investigate with a theological framework. Second, this topic synthesises huge amounts of data on what we currently know about miracles from many different domains (bible studies, bible archeology, ethics) and constructs an theological framework that incorporates all of it. Third, it brings together many converging lines of theological evidence (archaeology, comparative religious studies, etc) to inform their theological hypothesis. And finally, the authors freely admit and highlight the weaknesses of their position, and ...

As you see, the same phrase can be used with not much change for other purposes. Words are the wall that bad hypothesis use to hide behind.

But you wrote the most important part, the part that makes it more than a just-so story

(crucially) provide a number of predictions inherent in their framework.

I would wish that they had a verification of these preditions, but well, at least it seems that they started ok.

Good luck!

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Ha, nice. Hopefully I can put forth some convincing arguments.

What are your thoughts on ritualization, as described here?


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