compositionality – Replicated Typo

James Hurford: Animals Do Not Have Syntax (Compositional Syntax, That Is)

After passing my final exams I feel that I can relax a bit and have the time to read a book again. So instead of reading a book that I need to read purely for ‘academic reasons’, I thought I’d pick one I’d thoroughly enjoy: James Hurford’s “The Origins of Grammar“, which clocks in at a whopping 808 pages.
I’m still reading the first chapter (which you can read for free here) but I thought I’d share some of his analyses of “Animal Syntax.”
Hurford’s general conclusion is that despite what you sometimes read in the popular press,

“No non-human has any semantically compositional syntax, where the form of the syntactic combination determines how the meanings of the parts combine to make the meaning of the whole.”

The crucial notion here is that of compositionality. Hurford argues that we can find animal calls and songs that are combinatorial, that is songs and calls in which elements are put together according to some kind of rule or pattern. But what we do not find, he argues, are the kinds of putting things together where the elements put together each have a specified meaning and the whole song, call or communicative assembly “means something which is a reflection of the meanings of the parts.”

(Link)
To illustrate this, Hurford cites the call system of putty-nosed monkeys (Arnold and Zuberbühler 2006). These monkeys have only two different call signals in their repertoire, a ‘pyow’-sound that ‘means’, roughly, ‘LEOPARD’; and a ‘hack’ sound that ‘means’, roughly, ‘EAGLE’.

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Compositionality and Bilingualism

Last week I put up a link to an online experiment. Here’s the results! You can still do the experiment first, if you like, here. Source code and raw results at the bottom.

Languages evolve over time under a pressure to be learned by a new generation. Does learning two languages at once effect this pressure? My experiment says … maybe.

These pressures include ones for learnability (compression) and expressivity (able to express a large variety of meanings, Kirby, Cornish & Smith, 2008). Bilingualism seems like an unlikely ability since learning an extra language leaves the speaker potentially no more expressive at a cost of an increase in the amount of effort required to learn it. There is no pressure for one language structure (e.g. English) to adapt to another language (e.g. Mandarin) so that they can become optimally learnable and expressive as a single medium. That is, there’s no reason to assume that expressivity and learnability pressures apply across languages (which are not being used by the same people).

Nevertheless, children display an aptitude and a willingness to learn and use multiple languages simultaneously, and at a similar rate to monolingual children. Therefore, languages do seem to have adapted to be learnable simultaneously. Does the compatibility of languages point to a strong innate property of language? In contrast, it might point to underlying similarity in the structure of languages, brought about by universal principles of communication.

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Bonobos Extract Meaning from Call Sequences

A new study appeared yesterday on PlosOne by Clay and Zuberbühler of St Andrews University on the communicative ability of bonobos.

Studies have been done in the past on language-trained bonobos such as Kanzi which have revealed some remarkable abilities that the species has with regards to representational and communication tasks.

These studies have focussed on trained apes which are reared in unnatural environments and extensively trained on artificial languages. This has produced some interesting results though research into bonobos’ natural communication has been thin on the ground until now.

Clay and Zuberbühler address this gap in the research with a playback study on the natural vocal communication of bonobos.

Bonobos are known to produce five distinct vocal signals when finding food, these have been demonstrated to be combined together to make longer call sequences. The study found that individual call types were poor indicators of food quality but that calls which displayed a concatenation of signals were much better indicators.

The study looked into whether receivers could extract meaning about the quality of food encountered by the caller by integrating across different call sequences.

They started by training four captive bonobos to find two types of foods in two different locations, those which are more preferred such as kiwis and those which are less preferred such as apples. The apes were recorded when finding these different food types and these recordings were used in the playback experiments. When the bonobos discovered their preferred food they emitted higher pitched long barks and short “peeps” and when they discovered the less-preferred food they made lower pitch “peep-yelps” and yelps. Sequences of the four calls which used different compositions were played back to bonobos who were familiar with those apes who had originally made the calls. All sequences contained the same number of calls. In response to these playbacks the study found that the apes devoted significantly more effort and time searching the space which was known to contain the food type indicated by the call sequence (shown in the graph below).

The bonobos were shown to attend not just to individual calls but to the entire sequences before they made inferences about the food encountered by a caller.

These results provide the first empirical evidence that bonobos are able to extract information about external events by attending to natural vocal sequences made by other bonobos. This study really highlights the importance of call combinations in their natural communication system.

References
Clay Z, Zuberbühler K, 2011 Bonobos Extract Meaning from Call Sequences. PLoS ONE 6(4): e18786. doi:10.1371/journal.pone.0018786

Evolving Linguistic Replicators: Major Transitions and Grammaticalisation

Just before Christmas I found myself in the pub speaking to Sean about his work on bilingualism, major transitions and the contrast between language change and the cultural evolution of language. Now, other than revealing that our social time is spent discussing our university work, the conversation brought up a distinction not often made: whilst language change is part of language evolution, the latter is also what we consider to be a major transition. As you evolutionary biologists will know, this concept is perhaps best examined and almost certainly popularised in Maynard Smith & Szathmáry’s (1995) The Major Transitions in Evolution. Here, the authors are not promoting the fallacy of guided evolution, where the inevitable consequence is increased and universal complexity. Their thesis is more subtle: that some lineages become more complex over time, with this increase being attributable to the way in which genetic information is transmitted between generations. In particular, they note eight transitions in the evolution of life:

What’s notable about these transitions, and why they aren’t necessarily an arbitrary list, is that all of them share some broad commonalities, namely:

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Experiments in communication pt 2: Human Iterated Learning

In the last post, I discussed some of the literature into experimental communication, with the intention of then following it up by looking at recent experiments done at Edinburgh (and beyond). But as Hannah pipped me to the post, with a great overview of the wide range of experiments into language evolution, I’ll instead limit this to two relatively recent papers on Human Iterated Learning (Kirby et al., 2008; Cornish et al., 2009)

Drawing from experimental approaches found in Diffusion Chain and Artificial Language Learning studies, Kirby et al (2008) show that as a consequence of intergenerational transmission languages “culturally evolve in such a way as to maximize their own transmissibility: over time, the languages in our experiments become easier to learn and increasingly structured.” In these experiments a subject is exposed to an alien language, made up of two elements within a finite space: meanings (consisting of a picture with three discernible elements: colour, shape and movement) paired with signals (consisting of a string of letters). Importantly, the subject is only exposed to a set amount of meanings (SEEN items), after which they are then presented with a group of meanings (some SEEN, some UNSEEN) without the corresponding signal — the goal being that they provide a response (be it the correct version or not). On completion of forming the meaning-signal pairs the experiment is repeated, except this time the new subjects are trained on the data provided by the previous generation. This continues until the experiment is finished, which in this case happened at generation ten.

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Iterated Learning and Language Evolution

If we accept that language is not only a conveyer of cultural information, but it is itself a socially learned and culturally transmitted system, then an individual’s linguistic knowledge is the result of observing the linguistic behaviour of others. This well attested process of language acquisition is often termed Iterated Learning, and it opens up a new avenue to investigate the design features of language: that cultural, as opposed to biological, evolution is fundamental in understanding these features.

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Language as a complex adaptive system

A prominent idea in linguistics is that humans have an array of specialised organs geared towards the production, reception and comprehension of language. For some features, particularly the physical capacity to produce and receive multiple vocalizations, there is ample evidence for specialisation: a descended larynx (Lieberman, 2003), thoracic breathing (MacLarnon & Hewitt, 1999), and several distinct hearing organs (Hawks, in press). Given that these features are firmly in the domain of biology, it makes intuitive sense to apply the theory of natural selection to solve the problem: humans are specially adapted to the production and reception of multiple vocalizations.

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