Science – Page 15 – Replicated Typo

Are mirror neurons the basis of speech perception?

The discovery of Mirror Neurons in Macaque monkeys has lead to theories of the neurophysiological substrate of speech perception being grounded in mirror neurons. This is also relevant to the evolution of speech as if ability to perceive a rapid stream of phonemes is present in species such as macaques then this provides a foundation on which other linguistic abilities could have been built to form language.

A recent paper by Rogalsky et al. (2011) explores these theories by testing the hypothesis that damage to the human mirror system should cause severe deficits in speech perception. This is due to there being a number of recent studies which explore whether the areas of motor neurons are activated during speech perception but these do not address the prediction that patients with lesions in the motor regions (left posterior frontal lobe and/or inferior partiental lobule) should lack an ability to perceive speech.

Patients with Broca’s aphasia are well documented as having severe speech perception and Broca’s area is known to be an area of motor speech perception. This sets up a link between a lesions involving Broca’s area and a difficulty in speech perception. However, despite these problems in speech perception, it has been shown that Broca’s aphasics are quite capable of processing speech sounds. This creates a problem for motor theories of speech perception as it would predict the ability to percieve speech sounds when the lesion lies in Broca’s area. Rogalsky et al. (2011) states that this conclusion may not be so reliable as a lot of the group based studies which these conclusions have been drawn from do not present detailed lesion information but instead rely on clinical diagnosis of Broca’s aphasia to infer lesion location.

Rogalsky et al. (2011) present 5 cases of people with lesions which effect areas of mirror neurons.

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Project Nim

How cool is this? They’ve made a movie about Nim Chimpsky called Project Nim!

By the same guys who made Man on Wire, it’s currently been shown at the Sundance Festival.

Nim was raised and nurtured like a human child in order to see to what extent apes could acquire human language.

Following Nim’s extraordinary journey through human society, and the enduring impact he makes on the people he meets along the way, the film is an unflinching and unsentimental biography of an animal we tried to make human. What we learn about his true nature – and indeed our own – is comic, revealing and profoundly unsettling.

http://sundance.slated.com/2011/films/projectnim_sundance2011

Imitation and Social Cognition in Humans and Chimpanzees (II): Rational Imitation in Human Infants and Human-Raised Chimps

In my last post I wrote about two experiments on imitation in young children and chimpanzees by Lyons et al. (2005) and Horner & Whiten (2005). Their results suggested that young children tend to copy both the ‘necessary’ and the ‘unnecessary’ parts of a demonstrator’s action who shows them how to get a reward out of a puzzle box, whereas chimps only copy the ones necessary to get the reward.

ResearchBlogging.org One important question raised by these experiments was whether these results can only be applied to wild chimpanzees or whether they also hold for enculturated, human-raised chimps. This is an important question because it is possible that chimpanzees raised in these kinds of richly interactive contexts show more sensitivity to human intentionality.

Buttelman et al. (2007) tested just that. They used the “rational imitation” paradigm, which features two conditions

a) the subjects are shown an action in which the specific manner of the action is not purposive and intentional but results from the demonstrator being occupied with something else. For example, he may be carrying something so that he has to use his foot to turn on a light (often called the Hands Occupied Condition).

b) the subjects are shown an action in which the demonstrator chooses a specific manner of doing something on purpose. For example he may have his hands free but still choosto turn on the light with his foot (Hands Free Condition).

taken from Call & Tomasello 2008

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The Genesis of Grammar

In my previous post on linguistic replicators and major transitions, I mentioned grammaticalisation as a process that might inform us about the contentive-functional split in the lexicon. Naturally, it makes sense that grammaticalisation might offer insights into other transitions in linguistics, and, thanks to an informative comment from a regular reader, I was directed to a book chapter by Heine & Kuteva (2007): The Genesis of Grammar: On combining nouns. I might dedicate a post to the paper in the future, but, as with many previous claims, this probably won’t happen. So instead, here is the abstract and a table of the authors’ hypothesised grammatical innovations:

That it is possible to propose a reconstruction of how grammar evolved in human languages is argued for by Heine and Kuteva (2007). Using observations made within the framework of grammaticalization theory, these authors hypothesize that time-stable entities denoting concrete referential concepts, commonly referred to as ‘nouns’, must have been among the first items distinguished by early humans in linguistic discourse. Based on crosslinguistic findings on grammatical change, this chapter presents a scenario of how nouns may have contributed to introducing linguistic complexity in language evolution.

Prairie Dog Communication

istockphoto.com A recent NPR radio show covered the research of the biosemiotician Con Slobodchikoff of the Univeristy of Arizone on prairie dog calls. The piece is very public-orientated, but still might be worth listening to.

We’ve all (I hope) heard of the vervet monkeys, which have different alarm calls for different predators, such as for leopard (Panthera pardus), martial eagle (Polemaetus bellicosus), and python (Python sebae). (Seyfarth et al. 1980) For each of these predators, an inherent and unlearned call is uttered by the first spectator, after which the vervet monkeys respond in a suitable manner – climb a tree, seek shelter, etc. It appears, however, that prairie dogs have a similar system, and that it is a bit more complicated.

Slobodchikoff conducted a study where three girls (probably underpaid, underprivaleged, and underappreciated (under)graduate students) walked through a prairie dog colony wearing shirts of the colors green, yellow, and blue. The call of the first prairie dog to notice them was recorded, after which the prairie dogs all fled into their burrows. The intern then walked through the entire colony, took a break for ten minutes, changed shirts, and did it again.

What is interesting is that the prairie dogs have significantly different calls (important, as they are pretty much exactly the same to human ears) for blue and yellow, but not for yellow and green. This is due to the dichromatic nature of praire dog eyesight (for a full study of the eyesight of retinal photoreceptors of subterranean rodents, consult Schleich et al. 2010). The distinction between blue and yellow is important, however, as there isn’t necessarily any reason that blue people are any more dangerous to praire dogs than yellow ones. “This in turn suggests that the prairie dogs are labeling the predators according to some cognitive category, rather than merely providing instructions on how to escape from a particular predator or responding to the urgency of a predator attack.” (Slobodchikoff 2009, pp. 438)

Another study was then done where two towers were built and a line was strung between them. When cut out shapes were slung down the line, the prairie dogs were able to distinguish a triangle from a circle, but not a circle from a square. So, the prairie dogs are not entirely perfect at encoding information. The conclusion still stands however that more information is encoded in the calls than is entirely relevant to a suitable reaction (unless one were to argue that evolutionary pressure existed on prairie dogs to distinguish blue predators from yellow ones.)

NPR labels this ‘prairiedogese’, which makes me shiver and reminds me of Punxatawney Pennsylvania, where Bill Murray was stuck on a vicious cycle in the movie Groundhog Day, forced every day to watch the mayor recite the translated proclamation of the Groundhog, which of course spoke in ‘groundhogese’. Luckily, however, there won’t be courses in this ‘language’.

References:

Schleich, C., Vielma, A., Glösmann, M., Palacios, A., & Peichl, L. (2010). Retinal photoreceptors of two subterranean tuco-tuco species (Rodentia, Ctenomys): Morphology, topography, and spectral sensitivity The Journal of Comparative Neurology, 518 (19), 4001-4015 DOI: 10.1002/cne.22440

Seyfarth, R., Cheney, D., & Marler, P. (1980). Monkey responses to three different alarm calls: evidence of predator classification and semantic communication Science, 210 (4471), 801-803 DOI: 10.1126/science.7433999

Slobodchikoff CN, Paseka A, & Verdolin JL (2009). Prairie dog alarm calls encode labels about predator colors. Animal cognition, 12 (3), 435-9 PMID: 19116730

Imitation and Social Cognition in Humans and Chimpanzees (I): Imitation, Overimitation, and Conformity

Imitation is often seen as one of the crucial foundations of culture because it is the basis of social learning and social transmission. Only by imitating others and learning from them did human culture become cumulative, allowing humans to build and improve on the knowledge of previous generations. Thus, it may be one of the key cognitive specializations that sparked the success of the human evolutionary story:

Much of the success of our species rests on our ability to learn from others’ actions. From the simplest preverbal communication to the most complex adult expertise, a remarkable proportion of our abilities are learned by imitating those around us. Imitation is a critical part of what makes us cognitively human and generally constitutes a significant advantage over our primate relatives (Lyons et al. 2007: 19751).

Indeed, there have been some interesting experiments suggesting that the human capacity -and, above all, motivation – for imitation is an important characteristic that separates us from the other great apes.

In a series of intriguing experiments by Victoria Horner and Andrew Whiten from the University of St. Andrews in Scotland, and Derek Lyons and his colleagues from Yale University, young wild-born chimpanzees and Children aged 3 to 4 were shown how to get a little toy turtle/ a reward out of a puzzle box. In the first condition of the experiment the puzzle box was transparent, whereas in the second condition the puzzle box was opaque.

And here’s the catch: both chimpanzees and children were not shown the ‘right’ or ‘simple’ solution to how to get the reward but one that was actually more complicated and involved unnecessary steps.

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Dialects in Tweets

A recent study published in the proceedings of the Empirical Methods in Natural Language Processing Conference (EMNLP) in October and presented in the LSA conference last week found evidence of geographical lexical variation in Twitter posts. (For news stories on it, see here and here.) Eisenstein, O’Connor, Smith and Xing took a batch of Twitter posts from a corpus released of 15% of all posts during a week in March. In total, they kept 4.7 million tokens from 380,000 messages by 9,500 users, all geotagged from within the continental US. They cut out messages from over-active users, taking only messages from users with less than a thousand followers and followees (However, the average author published around 40~ posts per day, which might be seen by some as excessive. They also only took messages from iPhones and BlackBerries, which have the geotagging function. Eventually, they ended up with just over 5,000 words, of which a quarter did not appear in the spell-checking lexicon aspell.

In order to figure out lexical variation accurately, both topic and geographical regions had to be ascertained. To do this, they used a generative model (seen above) that jointly figured these in. Generative models work on the assumption that text is the output of a stochastic process that can be analysed statistically. By looking at mass amounts of texts, they were able to infer the topics that are being talked about. Basically, I could be thinking of a few topics – dinner, food, eating out. If I am in SF, it is likely that I may end up using the word taco in my tweet, based on those topics. What the model does is take those topics and figure from them which words are chosen, while at the same time figuring in the spatial region of the author. This way, lexical variation is easier to place accurately, whereas before discourse topic would have significantly skewed the results (the median error drops from 650 to 500 km, which isn’t that bad, all in all.)

The way it works (in summary and quoting the slide show presented at the LSA annual meeting, since I’m not entirely sure on the details) is that, in order to add a topic, several things must be done. For each author, the model a) picks a region from P( r | ∂ ) b) picks a location from P( y | lambda, v ) and c) picks a distribution over P( Theta | alpha ). For each token, it must a) pick a topic from P( z | Theta ), and then b) pick a word from P( w | nu ). Or something like that (sorry). For more, feel free to download the paper on Eisenstien’s website.

Well, what did they find? Basically, Twitter posts do show massive variation based on region. There are geographically-specific proper names, of course, and topics of local prominence, like taco in LA and cab in NY. There’s also variation in foreign language words, with pues in LA but papi in SF. More interestingly, however, there is a major difference in regional slang. ‘uu’, for instance, is pretty much exclusively on the Eastern seaboard, while ‘you’ is stretched across the nation (with ‘yu’ being only slightly smaller.) ‘suttin’ for something is used only in NY, as is ‘deadass’ (meaning very) and, on and even smaller scale, ‘odee’, while ‘af’ is used for very in the Southwest, and ‘hella’ is used in most of the Western states.

Screen shot 2011-01-12 at 23.41.24 — Dialectical variation for 'very'

More importantly, though, the study shows that we can separate geographical and topical variation, as well as discover geographical variation from text instead of relying solely on geotagging, using this model. Future work from the authors is hoped to cover differences between spoken variation and variation in digital media. And I, for one, think that’s #deadass cool.

Jacob Eisenstein, Brendan O’Connor, Noah A. Smith, & Eric P. Xing (2010). A Latent Variable Model for Geographic Lexical Variation. Proceedings of EMNLP

Recursion: what is it, who has it, and how did it evolve?

Hello Hello and Happy New Year,

So a new article appeared on the internet late last year by Coolidge, Overmann and Wynn (2010) (hereafter referred to as COW because it makes me smile). It’s a really short sweet little paper and you should read it as recursion is perhaps one of the hottest topics around language evolution. This generally stems from Hauser, Chomsky and Fitch’s (HCF, 2002) claim that it is the only feature of language unique to humans. I thought it would be useful to outline some of the issues surrounding it as put forward by the COW paper due to its high-profile, controversial and important position within current issues in language evolution.

History

Recursion was first talked about within the field of linguistics by Bar-Hillel in 1953. This was before Chomsky included the concept in his Generative Grammar in 1956.

It wasn’t until 2002 that HCF made the claim that recursion was the only feature of language which was included in the faculty of language in the narrow sense (FLN) and was therefore unique to humans.

Definition

The article outlines two definitions of recursion (within linguistics):

(1) embeddedness of phrases within other phrases, which entails keeping track of long-distance dependencies among phrases

(2) the speciﬁcation of the computed output string itself, including meta-recursion, where recursion is both the recipe for an utterance and the overarching process that creates and executes the recipe

I always worry when there is more than one definition for a thing because this often results in people talking past eachother or getting confused within their own arguments. These definition are also important to define before one starts making claims about whether recursion is present in species outside of humans or what people are talking about when referring to the evolution of recursion.

Evolutionary Scenarios

The paper also outlines two evolutionary scenarios for the adaptive value of recursion in human language.

(1) The gradualist position posits precursors, such as animal communication and protolanguages, and holds that the selective purpose of recursion was for communication.

(2) The saltationist position assumes no gradual development of recursion and posits that it evolved for reasons other than communication

The latter of these is the stand point taken by the HCF paper. Reasons for recursion evolving if one discounts communication could include the increase of working memory for other reasons or spacial navigation.

Pinker and Jackendoff (2005) argue that since recursion only exists in language to express recursive thoughts it must have pre-existed language.

COW (2010) points out that this is all very well but the question remains of what are recursive thoughts and why are they adaptive? These recursive acts may exist for the purposes of diplomatic speech, perlocutionary acts or for prospective memory and cognition (these are discussed at greater length in COW). These assume that the adaptive force was a social one which before Pinker and Jackendoff was not considered because recursion is often understood away from the social context of speech acts in the realm of mathematics.

Unique to Humans?

An often cited example debunking recursion’s importance to human language is the Piraha tribe who apparently do not have it (Everett 2005). The data from Everett is anecdotal, from one source and sketchy. Even if one was to accept the claims of lack of recursion they can be attributed to other factors such as cultural constraints or (although I think this is going a bit far, but then Bickerton always does go a bit too far) claiming the Piraha tribe have an underlying neurophysiological deﬁciency such as a limited working memory capacity or an extreme case of acquisitional delay.

COW then covers several animal studies which claim that recursion is present in animals including starlings and various monkeys. These are subject to the claim that the ability to acquire a phrase structure grammar means the presence of recursive ability (which is bollocks). These studies also fall short when one considers that starling’s songs are used to communicate emotional states, not recursive thoughts.

References

Bar-Hillel Y. (1953) On recursive definitions in empirical science. Proceedings of the 11th International Congress of Philosophy, Brussels. 1953, 5:160–165.

Coolidge, F., Overmann, K., & Wynn, T. (2010). Recursion: what is it, who has it, and how did it evolve? Wiley Interdisciplinary Reviews: Cognitive Science DOI: 10.1002/wcs.131

Hauser MD, Chomsky, N, Fitch (2002) The faculty of language: what is it, who has it and how did it evolve? Science, 298:1569-1579

http://www.st-andrews.ac.uk/~wtsf/downloads/HCF2002.pdf

Top-down vs bottom-up approaches to cognition: Griffiths vs McClelland

There is a battle about to commence. A battle in the world of cognitive modelling. Or at least a bit of a skirmish. Two articles to be published in Trends in Cognitive Sciences debate the merits of approaching cognition from different ends of the microscope.

On the side of probabilistic modelling we have Thom Griffiths, Nick Chater, Charles Kemp, Amy Perfors and Joshua Tenenbaum. Representing (perhaps non-symbolically) emergentist approaches are James McClelland, Matthew Botvinick, David Noelle, David Plaut, Timothy Rogers, Mark Seidenberg and Linda B. Smith. This contest is not short of heavyweights.

However, the first battleground seems to be who can come up with the most complicated diagram. I leave this decision to the reader (see first two images).

The central issue is which approach is the most productive for explaining phenomena in cognition. David Marr’s levels of explanation include the ‘computational’ characterisation of the problem, an ‘algorithmic’ description of the problem and an ‘implementational’ explanation which focusses on how the task is actually implemented by real brains. Structured probabilistic takes a ‘top-down’ approach while Emergentism takes a ‘bottom-up’ approach.

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Fungus, -i. 2nd Decl. N. Masculine – or is it?: On Gender

In an attempt to write out my thoughts for others instead of continually building them up in saved stickies, folders full of .pdfs, and hastily scribbled lecture notes, as if waiting for the spontaneous incarnation of what looks increasingly like a dissertation, I’m going to give a glimpse today of what I’ve been looking into recently. (Full disclosure: I am not a biologist, and was told specifically by my High School teacher that it would be best if I didn’t do another science class. Also, I liked Latin too much, which explains the title.)

It all started, really, with trying to get my flatmate Jamie into research blogging. His intended career path is mycology, where there are apparently fewer posts available for graduate study than in Old English syntax. As he was setting up the since-neglected Fungi Imperfecti, he pointed this article out to me: A Fungus Walks Into A Singles Bar. The post explains briefly how fungi have a very complicated sexual reproduction system.

Fungi are eukaryotes, the same as all other complex organisms with complicated cell structures. However, they are in their own kingdom, for a variety of reasons. Fungi are not the same as mushrooms, which are only the fruiting bodies of certain fungi. Their reproductive mechanisms is rather unexpectedly complex, in that the normal conventions of sex do not apply. Not all fungi reproduce sexually, and many are isogamous, meaning that their gametes look the same and differ only in certain alleles in certain areas called mating-type regions. Some fungi only have two mating types, which would give the illusion of being like animal genders. However, others, like Schizophyllum commune, have over ten thousand (although these interact in an odd way, such that they’re only productive if the mating regions are highly compatible (Uyenoyama 2005)).

Some fungi are homothallic, meaning that self-mating and reproduction is possible. This means that a spore has within it two dissimilar nuclei, ready to mate – the button mushroom apparently does this (yes, the kind you buy in a supermarket.) Heterothallic fungi, on the other hand, merely needs to find another fungi that isn’t the same mating type – which is pretty easy, if there are hundreds of options. Other types of fungi can’t reproduce together, but can vegetatively blend together to share resources, interestingly enough. Think of mind-melding, like Spock. Alternatively, think of mycelia fusing together to share resources.

In short, the system is ridiculously confusing, and not at all like the simple bipolar genders of, say, humans (if we take the canonical view of human gender, meaning only two.) I’m still trying to find adequate research on the origins of this sort of system. Understandably, it’s difficult. Mycologists agree:

“The molecular genetical studies of the past ten years have revealed a genetic fluidity in fungi that could never have been imagined. Transposons and other mobile elements can switch the mating types of fungi and cause chromosonal rearrangements.Deletions of mitochondrial genes can accumulate as either symptomless plasmids or as disruptive elements leading to cellular senescence…[in summary,] many aspects of the genetic fluidity of fungi remain to be resolved, and probably many more remain to be discovered.” (Deacon, 1997: pg. 157)

At this point you’re probably asking why I’ve posted this here. Well, perhaps understandably, I started drawing comparisons between mycologic mating types and linguistic agreement immediately. First, mating-type isn’t limited to bipolarity – neither is grammatical gender. Nearly 10% of the 257 languages noted for number of genders on WALS have more than five genders. Ngan’gityemerri seems to be winning, with 15 different genders (Reid, 1997). Gender distinctions generally have to do with a semantic core – one which need not be based on sex, either, but can cover categories like animacy. Gender can normally be diagnosed by agreement marking, which, taking out genetic analysis of the parent, could be analogic to fungi offspring. Gender can be a fluid system, susceptible to decay, mostly through attrition, but also to reformation and realignment – the same is true of mating types. (For more, see Corbett, 1991)

As with all biologic to linguistic analogues, the connections are a bit tenuous. I’ve been researching fungal replication partly for the sake of dispelling the old “that’s too complex to have evolved” argument, which is probably the most fun point to argue against creationists with. However, I’ve mostly been doing this because fungi and linguistic gender distinctions are just so damn interesting.

If anyone likes, I’ll keep you updated on mycologic evolution and the linguistic analogues I can tentatively draw. For now, though, I’ve really got to get back to studying for my examination in two days. Which means I’ve got to stop thinking about a future post involving detailing why “Prokaryotic evolution and the tree of life are two different things” (Baptiste et al., 2009)…

References:

Corbett, G. Gender. Cambridge University Press, Cambridge: 1991.
Deacon, JW. Modern Mycology. Blackwell Science, Oxford: 1997.
Reid, Nicholas. and Harvey, Mark David, Nominal classification in aboriginal Australia / edited by Mark Harvey, Nicholas Reid John Benjamins Pub., Philadelphia, PA : 1997.

Uyenoyama, M. (2004). Evolution under tight linkage to mating type New Phytologist, 165 (1), 63-70 DOI: 10.1111/j.1469-8137.2004.01246.x
Bapteste E, O’Malley MA, Beiko RG, Ereshefsky M, Gogarten JP, Franklin-Hall L, Lapointe FJ, Dupré J, Dagan T, Boucher Y, & Martin W (2009). Prokaryotic evolution and the tree of life are two different things. Biology direct, 4 PMID: 19788731