Chimpanzees Ha Ha Ha

Laughter is a contagious social vocalisation that punctuates everyday life with happiness. But do other animals laugh? And how does it happen?

400px-Laughter

Laughter is a natural, contagious social interation.

Did you know that females laugh more than males in conversations involving males and females? I know that sometimes girls laugh a bit more to boost a guy’s ego – apparently it’s an innate reaction to a potential mate, the more a girl laughs in a conversation, the better the signs are that she’s attracted to her male conversation partner. According to this paper, women seek out men to make them laugh, and the men that are best at doing this are often ‘dominant males’. So guys, if you’ve got the ladies laughing, it’s a good sign. After all, laughter is a really honest reaction – how many times have you not been able to control that snort or giggle when really, you should’ve kept quiet?

Something called the ‘punctuation effect’ shows that laughter and speech arise from the same vocal mechanism, controlled by the same neurological processes. The ‘punctuation effect’ refers to the fact you are more likely to laugh at the end of a sentence (where punctuation should be) and to have a short time delay between a phrase of a sentence and a giggle.

Laughter isn’t unique to humans! I didn’t know this. I knew about ‘happy sounds’ that animals make, my pet guinea pig used to ‘chirrup’ when he was content and everyone knows about a purring cat – but laughter? Now that’s cool. Not so surprisingly perhaps, are the types of animals that laugh – those closest to humans, chimpanzees and other great apes. Darwin reported of this ape laughter back in the late 19th Century. Tickling is the physical contact that is almost guaranteed to cause laughter and chimps also respond with laughter to being tickled.

Family

Chimpanzees laugh in a social context too.

The laughter of a chimp and that of a human do differ significantly, and this is one of the main reasons why we can speak and they can’t – breath control. Human laughter is usually a series of ‘ha-ha’ sounds on an outward breath, whereas chimps can only make one noise on an outward breath. Unlike humans, chimps still move around on all fours and their vocal and breathing system is heavily tied to their movement system. The position of a chimp’s thorax is such that it needs to brace itself for forearm impact – when it’s running, it takes one breath per stride. Humans have evolved to be bipedal and so can change this ratio of breaths per stride – we can make multiple sounds out of one outward breath, this led to the evolution of speech for our ancestors.

Laughing is one of the most natural parts of human vocalisation, and apparently it’s natural to chimps too!

I got the source for this post from a short paper by Robert Provine that straddles psychology and evolutionary science.

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