biases – Page 2 – Replicated Typo

Evolution of Colour Terms: Part 1

In a series of posts, I’ll review the current state of the field of the Evolution of Colour Categories. It has been argued that universals in colour naming across cultures can be traced back to constraints from many domains including genetic, perceptual and environmental. I’ll review these arguments and show that if our perception is affected by our language, then many conflicts can be resolved. Furthermore, it undermines the Universalist assumption that universal patterns in colour terms are evidence for innate constraints.

Part 1: Domains of Constraint

Genetic Constraints

Environmental Constraints

Perceptual Constraints

Learning Constraints

Cultural Constraints

Categorisation Constraints

Part 2: Universal patterns are not evidence for innate constraints

Perceptual Warping

Embodied Relationships

Niche Construction

Universal Patterns are not Evidence for Innate Constraints

For the full dissertation and for references, go here.

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Language Evolution and Language Acquisition

The way children learn language sets the adaptive landscape on which languages evolve. This is acknowledged by many, but there are few connections between models of language acquisition and models of language Evolution (some exceptions include Yang (2002), Yu & Smith (2007) and Chater & Christiansen (2009)).

However, the chasm between the two fields may be getting smaller, as theories are defined as models which are both more interpretable to the more technically-minded Language Evolutionists and extendible into populations and generations.

Also, strangely, models of word learning have been getting simpler over time. This may reflect a move from attributing language acquisition to specific mechanisms towards a more general cognitive explanation. I review some older models here, and a recent publication by Fazly et al.

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Bayesian Bilingualism

Recently, David Burkett and Tom Griffiths have looked at iterated learning of multiple languages from multiple teachers (Burkett & Griffiths 2010, see my post here). Here, I’ll describe a simpler model which allows bilingualism. I show that, counter-intuitively, bilingualism may be more stable than monolingualism.

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Learning Multiple languages from Multiple teachers

As Niyogi & Berwick (2009) point out, there is a tendency in modelling of Linguistic Evolution to assume chains of single learners inheriting single grammars from single teachers. This is, of course, not realistic – we learn language from many people and people can speak more than one language. However, Niyogi & Berwick suggest deeper objections.

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Words as alleles: A null-model for language evolution?

For me, recent computational accounts of language evolution provide a compelling rationale that cultural, as opposed to biological, evolution is fundamental in understanding the design features of language. The basis for this rests on the simple notion of language being not only a conveyor of cultural information, but also a socially learned and culturally transmitted system: that is, an individual’s linguistic knowledge is the result of observing the linguistic behaviour of others. Here, this well-attested process of language acquisition, often termed Iterated Learning, emphasises the effects of differential learnability on competing linguistic variants. Sounds, words and grammatical structures are therefore seen to be the products of selection and directed mutation. As you can see from the use of terms such as selection and mutation it’s clear we can draw many parallels between the literature on language evolution and analogous processes in biology. Indeed, Darwin himself noted such similarities in the Descent of Man. However, one aspect evolutionary linguists don’t seem to borrow is that of a null model. Is it possible that the changes we see in languages over time are just the products of processes analogous to genetic drift?

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Answering Wallace's challenge: Relaxed Selection and Language Evolution

How does natural selection account for language? Darwin wrestled with it, Chomsky sidestepped it, and Pinker claimed to solve it. Discerning the evolution of language is therefore a much sought endeavour, with a vast number of explanations emerging that offer a plethora of choice, but little in the way of consensus. This is hardly new, and at times has seemed completely frivolous and trivial. So much so that in the 19th Century, the Royal Linguistic Society in London actually went as far as to ban any discussion and debate on the origins of language. Put simply: we don’t really know that much. Often quoted in these debates is Alfred Russell Wallace, who, in a letter to Darwin, argued that: “natural selection could only have endowed the savage with a brain a little superior to that of an ape whereas he possesses one very little inferior to that of an average member of our learned society”.

This is obviously relevant for those of us studying language evolution. If, as Wallace challenged, natural selection (and more broadly, evolution) is unable to account for our mental capacities and behavioural capabilities, then what is the source behind our propensity for language? Well, I think we’ve come far enough to rule out the spiritual explanations of Wallace (although it still persists on some corners of the web), and whilst I agree that biological natural selection alone is not sufficient to explain language, we can certainly place it in an evolutionary framework.

Such is the position of Prof Terrence Deacon, who, in his current paper for PNAS, eloquently argues for a role for relaxed selection in the evolution of the language capacity. He’s been making these noises for a while now, as I previously mentioned here, with him also recognising evolutionary-similar processes in development. However, with the publication of this paper I think it’s about time I disseminated his current ideas in more detail, which, in my humble opinion, offers a more nuanced position than the strict modular adaptationism previously championed by Pinker et al (I say previously, because Pinker also has a paper in this issue, and I’m going to read it before making any claims about his current position on the matter).

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Experiments in cultural transmission and human cultural evolution

For those of you familiar with the formal mathematical models of cultural evolution (Cavalli-Sforza & Feldman, 1981; Boyd & Richerson, 1985), you’ll know there is a substantive body of literature behind the process of cultural transmission. It comes as a surprise, then, that experiments in this area are generally lacking.

For instance, if we look at evolutionary biology, then there are many experiments into small-scale microevolutionary processes, such as natural selection, sexual selection, mutation and drift, which are then applied in showing how these processes generate population-level, macroevolutionary patterns. It follows then, that this sort of population-level thinking can be applied to cultural evolution: the forces and biases of cultural transmission can be studied experimentally to see if they fit with population-level patterns of cultural change documented by scientists. As the current paper by Mesoudi & Whiten (2008) notes, this potentially gives cultural transmission experiments added significance: “cultural transmission should not only be studied for its own sake (i.e. in order to better understand cultural transmission itself), but also in order to explain broader cultural patterns and trends, all as part of a unified science of cultural evolution”.

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Cumulative Culture Evolved to Rapidly Coordinate Novel Behaviours

In the deliberations over humanity and its perceived uniqueness, a link is frequently made between our ability to support a rich, diverse culture and the origin of complex human behaviour. Yet what is often overlooked in our view of these two, clearly connected phenomena is the thread that weaves them together: the ability to coordinate behaviour. We need only look at the products of our culture, from language to religion, to see that any variant we may deem successful is contingent on coordinating the behaviour of two or more individuals. Still, what is truly illuminating about this ability is that, far from being a uniquely human feature, the ability to coordinate behaviour is ubiquitous throughout the many organismal kingdoms.

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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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Current Issues in Language Evolution

As part of my assessment this term I’m to write four mock peer-reviewed items for a module called Current Issues in Language Evolution. It’s a great module run by Simon Kirby, examining some of the best food for thought in the field. Alone this is an interesting endeavour, after all we’re right in the middle of a language evolution renaissance, however, even cooler are the lectures, where students get to do their own presentations on a particular paper. I already did my presentation at the start of this term, on Dediu and Ladd’s paper, which went rather well, even if one of my slip ups did not go unnoticed (hint: always label the graphs). So, over the next few weeks, in amongst additional posts covering some of the presentations in class, I’ll hopefully be writing articles on these four five papers:

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