The Complex Language of Love

(September 20th, 2013) There are not many areas in which flies surpass humans. Of course, they are better at flying but who thought that they use a much more complicated communication system, too? Swiss scientists mathematically analysed the behaviour of courting flies and got surprising results.

Ask anyone and they will tell you that, compared to any other species, humans are superior. But are we really? And how are we superior? One argument points towards language - a trait quite unique and more complex than any other known communication system among animals. However, the humble fruit fly turned out to be a rather unexpected challenger of this idea. Researchers led by Ruedi Stoop, from the Institute of Neuroinformatics and Physics at ETH Zurich, Switzerland, and by Leonid Bunimovich from the School of Mathematics at Georgiatech, USA, have shown that, when it comes to communication, flies do not only have a vast vocabulary, their “language” is actually more complex than ours.

“In language, the relations of the things around us are essentially encapsulated by means of grammar. We therefore compared the strength of grammar offered by the human language with that of the body language of Drosophila during courtship. We found that Drosophila has, measured by standards of artificial language, i.e. computer language, a more powerful grammar at its disposition,” summarises Ruedi Stoop his group’s latest findings.

The experiment was simple enough; they filmed fruit flies in the midst of having sex. For their dataset, they used a total of fifty high-speed courtship videos, most lasting several minutes. Each courtship event was broken down into 37 “fundamental behavioural acts”, so-called “irreducible cycles of irreducible acts” - essentially behavioural building blocks that can be considered much like the words used in a language. According to their classification, Drosophila’s “sexual language” is at least as complex as human language. In fact, their results show that male flies have a more complex grammar than females, or, than even Swiss-German or Dutch.

For their experiment, Stoop and co. came up with a totally new technique: the world’s first mathematical definition of animal behaviour. Ruedi explains, “We have developed an approach that provides you with a clear definition of 'behaviour', showing how it is possible to define this 'soft' notion that was previously confined to the biological field, within a precise mathematical framework. In this sense, we see in the work a technical breakthrough that will lead to novel insights in biology.”

Their results send a blunt message: we have to find our superiority elsewhere; language is now also fly territory. Ruedi argues that a main implication of their work is that it forces us to re-think the difference between humans and animals. This brings us to the original question: are we superior to other species? Ruedi shares his thoughts on the matter. “To me, the essential observation seems to be that nature does not preclude animals from using equally powerful grammars in their communications. This implies for me that for answering this question, we must look for reasons beyond language structure, potentially in the realm of neuroscience.”

Despite the new findings, we are still special in our ability to be aware of our language, something that flies or other animals appear to lack. Ruedi argues that during evolution, anatomical changes led to the outsourcing of diverse functions to different parts of the brain, which provided us with a unique ability of the perception of infinite loops. “This is in distinction to animals that (as is shown by the Drosophila example) in principle do have these structures as well, but lack an awareness of them and do not use them purposefully. An indication of the importance of infinite loops for us can be seen in how they particularly fascinate children, as exemplified by the Swiss children rhyme: Es isch emol e Maa gsi, dä het e hohle Zahn ka, und in däm Zahn isch e Kischtli gsi, und in däm Kischtli isch e Zeedel gsi, und uf däm Zeedel isch gschtande: Es isch emol e Maa gsi... [Once, there was a man with a hollow tooth, and in this tooth there was a little box, and in this box there was a paper, on which was written: Once, there was a man.] It is hard to imagine an animal finding such a construct as fascinating as we do,” they write in their paper. So, despite their apparent complex language, flies probably cannot enjoy their language as much as we do. But maybe we humans can enjoy the complex language of flies on their behalf.

Karl Gruber

Picture: Fotolia/Style-o-Mat

Last Changes: 10.29.2013