Tag Archives: experiment

Octopus

Observational learning in octopus vulgaris

A few months ago, a documentary I saw on the Discovery Channel covered some research by Graziano Fiorito and colleagues at the Stazione Zoologica  in Naples. They were investigating observational learning in wild Octopus vulgaris with a puzzle-box experiment similar to those demonstrating cultural transmission in chimpanzees.

It goes like this: there’s a tasty and terrified crustacean running around in a perspex box that has two possible ways of being opened by hungry octopuses. The experimenters capture a wild octopus (let’s call him Steve) from the harbour (which I’ll get back to in a minute), and they put it in a tank with the puzzle-box. After Steve stares hopelessly at the box for a while, it is then removed from the tank. Steve the kidnapped octopus then gets to watch a captive octopus in the next tank being presented with the same puzzle-box containing the delicious crab. Of course, the captive octopus has been confronted with the puzzle-box enough times that it has worked out a successful solution, and so opens the box like a pro. Steve is then presented with a crab in a puzzle-box again, except this time he goes straight for the crab using the same solution he just learned from the captive octopus. Here is a clip from the documentary, showing a trial of this experiment (NB: not the best quality).

It turns out that the papers on this go back as far as Fiorito & Scotto 1992, and it seems this was the first time observational learning had been demonstrated in invertebrates. The reason I’m interested in reporting this is because the documentary I watched explained another possible motivation/interpretation for Fiorito’s work that I can’t find in any of his actual papers. The octopuses used in the experiments were all caught from the harbour at Naples just before the experiments, which of course controlled for any prior experience with the puzzle boxes. But the results were reported as particularly interesting because the Naples harbour had been overfished and disrupted, resulting in an increase in marine predators that eat the small octopus vulgaris as well as fish that the octopuses themselves rely on. These harsher environmental conditions resulted in the octopuses being forced to inhabit a smaller space alongside each other. As a result, young octopuses were frequently exposed to, and even coexisted with, older octopuses. This is a weird situation for an octopus; they usually live solitary lives and never even meet their own mothers, who die of starvation while caring for the eggs (the fathers die within a few months of having mated). The only real interactions are mating, and conflicts between rival males while competing for a mate.

Toward the end of the documentary, the voiceover growled against some dramatic music about how the combination of observational learning capacities and increased predation pushing octopuses into groups meant that it was only a matter of time  before we’re overthrown by octopus vulgaris. This made me think of Dunbar’s “social brain hypothesis” for the emergence of language, and whether I really should prepare to welcome our new octopus overlords. Talking specifically about primates, Dunbar (1996) states that “[primates] in general exhibit two responses to increased predation: they grow physically bigger [or] they increase the size of their groups” (p.110). In order to maintain these groups, that are essential for survival in harsh ecological conditions, Dunbar suggests that standard primate grooming behaviour becomes too time consuming and costly in order to keep up with the rapidly expanding social group, creating a pressure for a more efficient method of bonding and communicating that allows the size of the group to continue increasing. Again with reference just to primate communication, Dunbar says “This [efficient mechanism] need not have involved any dramatic change, for as the studies by Seyfarth and Cheney have shown, primate vocalizations are already capable of conveying a great deal of social information and commentary.” (p.115) In addition to primates, and adding further credence to this idea, it’s been shown that the older Matriarchs of elephant groups make use of vocalisations to seemingly instruct their group on how to fend off lion attacks (McComb et al., 2011; previous Replicated Typo coverage here). It seems to me that the difference between the primates/elephants and the octopuses is that the former endeavour to actually enrich the environment from which their conspecifics extract information; they don’t just learn, they inform. As far as we can tell, there is no such communication like this – that is, enriching the environment in some way that helps other octopuses learn or survive – happening among the octopuses. That said, we know from mating displays and conflicts that cephalopods can communicate with chromatophore signalling. As an interesting aside that is reflective of their cognitive abilities and capacity for suffering, octopuses are treated as honorary vertebrates by UK animal testing laws.

It’s interesting enough that marine biologists (or at least those reporting on marine biologists) seem to have the same idea as Dunbar about the necessary preconditions for successful societies of animals, but why not let’s get wildly speculative? If (..!) existing in groups is in fact adaptive for these octopuses in the face of increased predation, and the competition between them for resources isn’t too great a counter-factor, it seems the only ingredient missing from an octopocalypse is the emergence of some cooperative behaviour. Someone should keep an eye on that harbour.

 

References

Dunbar, R. (1996) Grooming, Gossip, and the Evolution of Language. Harvard University Press: Cambridge, Massachusetts

Fiorito, G. & Scotto, P. (1992) “Observational learning in Octopus vulgaris” Science 256, 545-546.

McComb, K., Shannon, G., Durant, S., Sayialel, K., Slotow, R., Poole, J. & Moss, C. (2011) “Leadership in elephants: the adaptive value of age” Proceedings of the Royal Society B, published online.

avml

Advances in Visual Methods for Linguistics (AVML2012)

Some peeps over the the University of York are organising a conference on the advances in visual methods for linguistics (AVML) to take place in September next year. This might be of interest to evolutionary linguists who use things like phylogenetic trees, networks, visual simulations or other fancy dancy visual methods. The following is taken from their website:

Linguistics, like other scientific disciplines, is centrally reliant upon visual images for the elicitation, analysis and presentation of data. It is difficult to imagine how linguistics could have developed, and how it could be done today, without visual representations such as syntactic trees, psychoperceptual models, vocal tract diagrams, dialect maps, or spectrograms. Complex multidimensional data can be condensed into forms that can be easily and immediately grasped in a way that would be considerably more taxing, even impossible, through textual means. Transforming our numerical results into graphical formats, according to Cleveland (1993: 1), ‘provides a front line of attack, revealing intricate structure in data that cannot be absorbed in any other way. We discover unimagined effects, and we challenge imagined ones.’ Or, as Keith Johnson succinctly puts it, ‘Nothing beats a picture’ (2008: 6).

So embedded are the ways we visualize linguistic data and linguistic phenomena in our research and teaching that it is easy to overlook the design and function of these graphical techniques. Yet the availability of powerful freeware and shareware packages which can produce easily customized publication-quality images means that we can create visual enhancements to our research output more quickly and more cheaply than ever before. Crucially, it is very much easier now than at any time in the past to experiment with imaginative and innovative ideas in visual methods. The potential for the inclusion of enriched content (animations, films, colour illustrations, interactive figures, etc.) in the ever-increasing quantities of research literature, resource materials and new textbooks being published, especially online, is enormous. There is clearly a growing appetite among the academic community for the sharing of inventive graphical methods, to judge from the contributions made by researchers to the websites and blogs that have proliferated in recent years (e.g. InfostheticsInformation is BeautifulCool InfographicsBBC Dimensions, or Visual Complexity).

In spite of the ubiquity and indispensability of graphical methods in linguistics it does not appear that a conference dedicated to sharing techniques and best practices in this domain has taken place before. This is less surprising when one considers that relatively little has been published specifically on the subject (exceptions are  Stewart (1976), and publications by the LInfoVisgroup). We think it is important that researchers from a broad spectrum of linguistic disciplines spend time discussing how their work can be done more efficiently, and how it can achieve greater impact, using the profusion of flexible and intuitive graphical tools at their disposal. It is also instructive to view advances in visual methods for linguistics from a historical perspective, to gain a greater sense of how linguistics has benefited from borrowed methodologies, and how in some cases the discipline has been at the forefront of developments in visual techniques.

The abstract submission deadline is the 9th January.

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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Categorising languages through network modularity

Today I’ve been learning more about network structure (from Cris Moore) and I’ve applied my poor understanding and overconfidence to find language families from etymology data!

Here’s what I understand so far (see Clauset, Moore, &  Newman, 2008):  The modularity of a network is a measure of how many ‘communities’ it has.  An optimal modularity will split the graph to maximise the average degree within modules or clusters.  You can search all the possible clusterings to find this optimum.  I’m still hazy on how this is actually done, and you can extend this to find hierarchies like phylogenetics, but without some assumptions.  Luckily, there’s a network analysis program called gephi that does this automatically!

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Replicated Hauser Results

Some of you may remember last summer Marc Hauser was found guilty of research misconduct. This investigation raised questions about several publications including a paper from 2007 in Science. This paper looked into the ability of non-human primates to understand the intentions of a human experimenter by interpreting his gestures.

Today Science has published a partial replication of the study in question which confirms the original findings that chimpanzees, cotton-top tamarins, and rhesus macaques can distinguish intentional gestures, such as pointing to indicate a container with food inside, from “accidental” actions such as a hand flopping against a container.

The Science wesite states the following:

Following the Harvard misconduct investigation, first author Justin Wood, now an assistant professor at the University of Southern California in Los Angeles, wrote to Science in June 2010 to notify the journal that the investigation had revealed that the original field notes for the rhesus experiments could not be found:

“An internal examination at Harvard University determined that there are no field notes, records of aborted trials, or subject identifying information associated with the rhesus monkey experiments; however, the research notes and videotapes for the tamarin and chimpanzee experiments were accounted for. Professor Hauser states that “most of the rhesus monkey observations were hand written by [co-author David D.] Glynn on a piece of paper, and then the daily results tallied and reported to Wood over email or by phone” and then the raw data were discarded. The research assistant who performed the experiments (Glynn) confirmed that these field notes were discarded.”

Hauser and Wood returned to Cayo Santiago island in Puerto Rico to redo the experiments from the 2007 paper with the same population of free-ranging rhesus monkeys. Their findings, including field notes and video trials, are available online and they essentially match those reported in the original paper.

It is still not known what went wrong with the original experiment, a statement issued by Science today only says the following:

We stress that this new publication aims only to determine whether the original rhesus monkey experiments from the 2007 paper can be replicated. It has no bearing on questions raised about Dr. Hauser’s larger body of work.

This article from Science Inside quotes Dario Maestriperi as saying:

“The results of this replication are straightforward and entirely consistent with those of the original study. If the authors’ interpretation of their results is correct, these findings are very important and represent one of the clearest demonstrations that nonhuman primates can interpret the behavior of other individuals as intentional or non-intentional….Since the experimenter who tested the rhesus monkeys in the replication study appeared from the video to be the first author on the paper, Justin Wood, he was clearly knowledgeable of the hypotheses being tested and had some strong expectations and desires about the monkeys’ performance on the test.”

So is this replication a clarification of groundbreaking findings or could the monkey’s behaviour be down to the Clever Hans effect?

Meanwhile investigations into Hauser’s research are still ongoing and he is still banned from teaching for the next academic year.

 

Cultural inheritance in studies of artifical grammar learning

Recently, I’ve been attending an artificial language learning research group and have discovered an interesting case of cultural inheritance.  Arthur Reber was one of the first researchers to look at the implicit learning of grammar.  Way back in 1967, he studied how adults (quaintly called ‘Ss’ in the original paper) learned an artificial grammar, created from a finite state automata.  Here is the grand-daddy of artificial language learning automata:

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The emergence of stable bilingualism in the lab: An experiment proposal

There is a huge amount of linguistic diversity in the world. Isolation and drift due to cultural evolution can explain much of this, but there are many cases where interacting groups use several languages. In fact, by some estimates, bilingualism is the norm for most societies. If one views language as a tool for communicating about objects and events, it seems strange that linguistic diversity should be maintained over time for two reasons. First, it seems more efficient, during language use, to have a one-to-one mapping between signals and meanings. In fact, mutual exclusivity is exhibited by young children and has been argued to be an innate bias and crucial to the evolution of a linguistic system. How or why do bilinguals over-ride this bias? Secondly, learning two language systems must be more difficult than learning one. What is the motivation for expending extra effort on learning an apparently redundant system?

Despite these obstacles, stable bilingualism exists in many parts of the world.   How might these arise and be maintained?  Continue reading

Elephants give each other a helping trunk

A study published on PNAS.org yesterday has shown that elephants might have shared goals which gives them the ability to co-operate.

An experiment was done using the classical 1930s cooperation paradigm used to test the co-operative abilities of monkeys and apes. This paradigm is used to explore the cognition underlying coordination toward a shared goal. This explores what animals know or learn about the benefits of cooperation and also tests their ability to comprehend a partner’s role in cooperation.

The experiment comprises of 2 animals who need to work together to pull 2 ends of the same rope in order to pull a platform towards them which holds a reward such as food.

Experiments such as this have never been done on animals apart from primates before. Plotnik et al. (2011) subjected this experimental paradigm to elephants and have shown that elephants can learn to coordinate with a partner. The elephants also delayed pulling he rope for up to 45 seconds if the arrival of their partner was delayed which showed that they comprehended that there was no point to pulling on the rope if their partner lacked access to the rope. The elephants learnt that this was the case much more quickly than has been shown in Chimpanzees in other studies.

Observations from the wild suggest that in nonhuman primates these co-operative abilities exist but experimental results have been mixed. Plotnik et al. (2011) claim that convergent evolution may have lead elephants to have reached a level of cooperative skill equal to that of chimpanzees.

You can see a video of the elephants doing the experiment here: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9417000/9417308.stm

References

Plotnik, J. M., R. Lair, w. Suphachoksahakun & F. B. M. de Waal (2011)
Elephants know when they need a helping trunk in a cooperative task. PNAS 2011 : 1101765108v1-201101765.

Emergence of linguistic diversity in the lab

There is a huge amount of linguistic diversity in the world. Isolation and drift due to cultural evolution can explain much of this, but there are many cases where linguistic diversity emerges and persists within groups of interacting individuals.  Previous research has identified the use of linguistic cues of identity as an important factor in the development of linguistic diversity (e.g. Nettle, 1999).  Gareth Roberts looks at this issue with an experimental paradigm.

This experiment was a game where individuals had to trade commodities in a series of rounds. At each round, individuals were paired up either with a team-mate or a competitor, though the speaker’s true identity was hidden.  Players were given random resources, but scored points based on how ‘balanced’ their resources were after trading (that is, you were punished for having much more meat than corn, for example).  A commodity given to another individual was worth twice as much to the receiver as to the donor.

Players could only interact through an ‘alien’ language via an instant-messaging system.  Prior to the game, individuals learned an artificial language which they were to use in these interactions. All participants were initially given the same starting language.  There were several conditions that manipulated the frequency with which you interacted with your team-mate and whether the task was competitive or co-operative.  In the co-operative condition, four players were considered as part of the same team and the task was to get a high a score as possible.  In the competitive condition the four players were split into two groups and the task was to score more than the other team.  In this condition, then, the main task was to identify whether your partner was a co-operator or a competitor.

The results showed that, if players interacted frequently enough with their team-mates and were in competition with another group, then linguistic diversity emerged.  Over the course of the game each team developed its own ‘variety’, and this was used as a marker of group identity. For example, in one game two forms of the word for ‘you’ arose.  Players in one team tended to use ‘lale’ while players in the other team tended to use ‘lele’, meaning that players could tell group membership from this variation.  Thus, linguistic variation arose due to the linguistic system evolving to encode the identity of the speakers.

The diversity seemed to arise both from drift and intentional change, both of which have been documented in the sociolinguistic literature.  Roberts suggests that linguistic markers make good social markers because they are costly to obtain (so difficult for free-riders to fake), salient and flexible enough to cope with changing group dynamics.  In the next post, I’ll be thinking about a similar experiment looking at how linguistic variation might arise in a co-operative scenario.

Roberts, G. (2010). An experimental study of social selection and frequency of interaction in linguistic diversity Interaction Studies, 11 (1), 138-159 DOI: 10.1075/is.11.1.06rob