culture

In last week's Science, Stanislas Dehaene and colleagues describe the relation of cultural invention to "universal intuition" about mathematical logic:

The mapping of numbers onto space is fundamental to measurement and to mathematics. Is this mapping a cultural invention or a universal intuition shared by all humans regardless of culture and education? We probed number-space mappings in the Mundurucu, an Amazonian indigene group with a reduced numerical lexicon and little or no formal education. At all ages, the Mundurucu mapped symbolic and nonsymbolic numbers onto a logarithmic scale, whereas Western adults used linear mapping with small or symbolic numbers and logarithmic mapping when numbers were presented nonsymbolically under conditions that discouraged counting. This indicates that the mapping of numbers onto space is a universal intuition and that this initial intuition of number is logarithmic. The concept of a linear number line appears to be a cultural invention that fails to develop in the absence of formal education (Dehaene et al. 2008:1217).

The idea is that children in Western societies have to learn that a number line is a linear representation; they begin by compressing the space devoted to large numbers:

When asked to point toward the correct location for a spoken number word onto a line segment labeled with 0 at left and 100 at right, even kindergarteners understand the task and behave nonrandomly, systematically placing smaller numbers at left and larger numbers at right. They do not distribute the numbers evenly, however, and instead devote more space to small numbers, imposing a compressed logarithmic mapping. For instance, they might place number 10 near the middle of the 0-to-100 segment. This compressive response fits nicely with animal and infant studies that demonstrate that numerical perception obeys Weber's law, a ubiquitous psychophysical law whereby increasingly larger quantities are represented with proportionally greater imprecision, compatible with a logarithmic internal representation with fixed noise (7, 20, 21). A shift from logarithmic to linear mapping occurs later in development, between first and fourth grade, depending on experience and the range of numbers tested (17-19).

They note that there's a problem testing these ideas in Western children, who are surrounded throughout their development by numbers -- in books, "elevators" and other places. Most of these numbers are small ones -- especially one through ten -- so they might naturally accentuate the ones they know.

They found when testing the Mundurucu that both adults and children tended to compress the high end of the number scale, even testing numbers between one and ten. This compression is logarithmic -- they accentuate contrasts between small numbers disproportionately. It makes sense logically -- we care more about detailed contrasts between small numbers than large numbers. They don't give an idea of which logarithm people are using; and in fact it may be different ones for different people. The important fact is the small number/large number contrast.

Dehaene and colleagues attribute this scaling to mapping at the neural level:

What are the sources of this universal logarithmic mapping? Research on the brain mechanisms of numerosity perception have revealed a compressed numerosity code, whereby individual neurons in the parietal and prefrontal cortex exhibit a Gaussian tuning curve on a logarithmic axis of number (27). As first noted by Gustav Fechner, such a constant imprecision on a logarithmic scale can explain Weber's law -- the fact that larger numbers require a proportional larger difference in order to remain equally discriminable. Indeed, a recent model suggests that the tuning properties of number neurons can account for many details of elementary mental arithmetic in humans and animals (21). In the final analysis, the logarithmic code may have been selected during evolution for its compactness: Like an engineer's slide rule, a log scale provides a compact neural representation of several orders of magnitude with fixed relative precision.

From that perspective, the Western conception of the number line appears as a very distinctive invention, capable of adjusting the logarithmic encoding to arrive at faster and more accurate mathematical conclusions about large numbers. The authors speculate that addition and subtraction (which display invariance between large and small numbers) and experience with measurement underlay the development of the linear concept in Western children.

References:

Dehaene S, Izard V, Spelke E, Pica P. 2008. Log or linear? Distinct intuitions of the number scale in Western and Amazonian indigene cultures. Science 320:1217-1220. doi:10.1126/science.1156540

The June Scientific American (no link available) has an article on page 32 about the "therapeutic value of blogging." That's some relief, after the stories a couple of months ago about blogging being potentially deadly.

And it's no small irony, considering that the article I found on the previous two pages had great potential to give me therapeutic opportunities here.

In the article, titled, "Need for speed?" David Biello wrote up some of the human genetics results of the past 6 months, placing them as a point-counterpoint presentation of our acceleration result.

First, he cites Gregory Cochran, who does as good a job explaining our result in one sentence as I've seen:

"We found very many human genes undergoing selection" ... "We believe that this can be explained by an increase in the strength of selection as people became agriculturalists, a major ecological change, and a vast increase in the number of favorable mutations as agriculture led to increased population size."

In that form, it is hard to see how anyone could disagree. Clearly, agriculture was a major ecological shift for humans, and it imposed new selection pressures associated with diet, disease, social organization and other ecological factors. At the same time, the population grew and more people meant more mutations. That's the story; the rest is detail filled in by anthropology, genomics, and math.

Biello then cites another recent study that partially confirms our results. That study, by Lluis Quintana-Murci and colleagues, found a much smaller number of selected genes (55), but what is important is that every one of these genes has an F_ST greater than 0.65. In other words, in every one of these cases, an allele that is vanishingly rare in most of the world has reached a frequency over 80 percent in one population. As allele frequencies go, these are extreme differences -- much, much larger than the average genetic difference between populations, characterized by an F_ST around 0.1. We also found a few such alleles in our survey of selected genes, but the vast majority of genes have not generated such extreme differences in frequency -- mainly because they haven't been around long enough. In other words, the Quintana-Murci study confirms the distribution of positively selected alleles, across the range where it overlaps with other studies, including ours.

Then Biello turns to the doubters. Noah Rosenberg coauthored a study earlier this year that reported polymorphism data from a sample of populations around the world.

"We are a young species," remarks geneticist Noah Rosenberg of the University of Michigan at Ann Arbor, who participated in a comprehensive study of genetic variation that appeared in Nature in February. "Different human populations have not been separated for long enough periods of time to develop their own new alleles."

Now, I never hold quotes in the press against people, because they represent a very small portion of what they may have said to a writer, and there are many opportunities for miscommunication. Still, I have to write about this, because it's about my work! So I'll try to describe the misconceptions illustrated by the article.

I am pretty sure that Rosenberg must know that his statement in the article is false. For one thing, "developing" a new allele is simply mutation, and mutation occurs continuously. All human populations have rare alleles that have originated recently and remain distributed only across small areas. Rosenberg's surveys of gene variation have identified many such alleles.

But more important to the current question, positive selection carries an allele to high frequency very rapidly -- much more quickly than the 50,000-year or longer span of time we are talking about. An allele with a five percent fitness edge can go from zero to fixation in several hundred generations -- in humans, they can make very large frequency changes in a thousand years.

If we took the quote at face value, Rosenberg would be saying that human evolution is impossible -- and that new selected alleles like lactase persistence and sickle cell simply cannot exist. We may be a young species (although I would argue the point), but that doesn't mean that we have stopped evolving!

Two prominent geneticists quoted in the article suggest that a bottleneck may explain the pattern of human genetic variation. Here also, I have to be cautious interpreting their quotes -- because even though they may seem relevant, they are referring to their own research papers, which don't actually address the question of linkage disequilibrium and positive selection.

Marcus Feldman suggests that a series of bottlenecks are a likely explanation for the pattern of human genetic variation, in particular, the decreasing gradient of genetic diversity with increasing distance from Africa. This is the "serial founder effect" scenario that I have written about before. I criticized Feldman's and other papers on this subject this spring, referring to "the Stanford school of genetic orthodoxy." My basic point is that all of the results are assumed to support the idea of bottlenecks: no one has yet tested the hypothesis. Even simulations that show the credibility of the concept do not test the hypothesis, because they do not examine credible alternatives, either demographic or selective.

More important, bottlenecks during the dispersal from Africa 50,000 years ago cannot possibly explain linkage blocks concentrated in coding genes with a mean age of 5500 years!

Why is there such difficulty understanding natural selection? I find it quite incredible that many of the scientists who would rail against ignoring Darwin in public schools at the same time actively root out Darwin's theory from their graduate students. Still, there it is. One prominent geneticist (I won't give the name) recently asked me, "You don't really think that lactase was selected, do you?" Many really believe that natural selection has stopped and that recent human evolution reflects nothing more than the cumulative effects of bottlenecks.

What is amazing to me is that these same geneticists embrace hypotheses of population history that cannot possibly have happened. The other geneticists quoted in the article, Carlos Bustamante and his graduate student Kirk Lohmueller, wrote a paper earlier this spring arguing that deleterious mutations have reached high frequency in Europeans (moreso than Africans) because of a bottleneck during European history. The press reported this work as "Whites genetically weaker than blacks, study finds." The hypothesis in the paper is that protein-coding sites otherwise conserved in most mammals may differ among humans because of relaxed selection in a bottleneck.

Here's why they're wrong: their bottleneck is impossible. They propose that the European population was a small, isolated population of 5,700 effective individuals from 214,000 years ago up to the Last Glacial Maximum. I suppose I should take some encouragement that they believe Neandertals were European ancestors (because otherwise, where exactly would this small, isolated population of Europeans have lived). But it's still quite impossible -- it implies no gene flow between Africans and Europeans across that entire span. You see, that is the only way that genetic drift can lead to this kind of result -- large differences in frequencies between continents for hundreds of deleterious alleles. It takes a bottleneck of exceptional length, along with complete isolation.

In what has become a troubling trend, these details were hidden away in the online supplementary information of the paper. It is no surprise that most people read only the paper's conclusions, without critically evaluating the methods. But when the assumptions are hidden so that it takes an effort to look at them, you can understand that the paper does not receive the kind of scrutiny that it deserves. These are not obscure laboratory techniques; they are the basic evidence on which the conclusions were based.

Now, Bustamante knows that positive selection has been very important in recent human evolution, because he wrote an important paper on the subject in 2005. I wrote about the paper at the time -- it was one of the works that really got us thinking about acceleration in the first place. So why in the world did their more recent paper adopt such a ridiculous model of population history?

In any event, I don't think that either of these studies from earlier this year are relevant to our acceleration results. They address different aspects of genetic variation. However, acceleration may help to explain the high frequencies of some gene variants conserved in other mammals -- the results explained by Lohmueller and colleagues as relaxed selection under a bottleneck.

The acceleration of recent positive selection would predict that many otherwise conserved gene variants may be segregating in humans, because they are the targets of positive selection. These conserved sites are among those most likely to show a strong sign of recent selection, because adaptive changes on them are necessarily rare (we know they're rare, because they haven't happened very often among other species). Most such sites are still conserved in humans -- it's just not possible to change their function in adaptive ways. But the massive ecological changes of recent human history have created the opportunity for adaptive responses that are not present in other mammalian lineages. We shouldn't be surprised to see that some such changes are currently underway.

Now, that's a different interpretation of the same data, and it's a testable hypothesis. Are these conserved sites in regions that show other signs of positive selection? If they are, then acceleration explains the data. I'm looking into it now.

I'm doing some research for an essay, which relies quite a bit on the work of Dobzhansky and a few of his contemporaries. There are some great quotes that I won't be using, but thought it would be worth passing on. Probably to the greatest extent among the architects of the Synthesis, Dobzhansky concerned himself with the relationship between genetic evolution and human cultural evolution.

In 1963, he published an essay in Current Anthropology addressing the relationship of anthropology and the natural sciences -- part of a forum that also addressed the relation of anthropology with the social sciences and humanities.

Man is a highly variable polytypic and polymorphic species. The genetic variability affects behavioral traits no less than physiological and structural ones, and it is false to imagine that these three categories are clearly separable. The chief reasons why so many people are loath to admit the genetic variability of social and culturally significant traits are two. First, human equality is stubbornly confused with identity, and diversity with inequality, as though to be entitled to an equality of opportunity, people would have to be identical twins. Human diversity is not incompatible with equality. Secondly, it is futile to look for one-to-one correspondence between cultural forms and genetic traits. Cultural forms are not determined by genes, but their emergence and maintenance are made possible by the genetically conditioned human diversity. The division of labor in human societies is primarily a cultural rather than a genetic phenomenon, but could it be sustained in a population consisting of persons genetically as similar as identical twins? This is not entirely a vain question, since at least one great geneticist has recently envisaged the possibility of bringing about such genetic uniformity (Dobzhansky 1963:147).

Later in the essay, Dobzhansky raised the problem of an excess of success -- namely, that human population growth and technology made it possible to avoid mortality that once selected against various "bad" genes. Various beliefs about this trend gave the impetus to early-20th-century eugenics, and were a continuing concern for "well-thinking" people. Would humans become victims of their own success? Dobzhansky responded in two ways. First, by noting that natural selection is hardly a savior:

Neither do I need to retell here the story of the alleged relaxation or suspension of natural selection in civilized mankind. The dangers from this source, although not necessarily exaggerated, have often been presented in a wrong perspective. A notion, which is less frequently stated explicitly than implied in many writings, is that the progress of mankind would be safe and even irresistible if only the natural selection were permitted to operate unobstructed by civilization and its amenities. This notion does not stand critical examination. Natural selection does not even insure that the species on which it acts will survive, let alone that it will improve, in any sense of the word "improvement." Dinosaurs became extinct, despite their evolution having been piloted by natural selection, quite unhampered by culture, medicine, or charity (Dobzhansky 1963:148).

Second, Dobzhansky addressed the real question: whether the current direction of genetic change is desirable:

Reproductive fitness is assuredly not the only virtue which we admire in men and would like them to possess. By its maintenance of the reproductive fitness, natural selection brings results which we, men, do not necessarily hold desirable. But to say that natural selection is suspended in mankind because we are not sure that man's biological evolution has assumed a direction to our liking, is to make the word "natural" selection biologically meaningless. Natural selection is automatic, mechanical, blind. It has brought about the evolution of the living world and the emergence of man with his capacity for culture, but it has no purpose because purposes are human prerogatives (Dobzhansky 1963:148).

He ends the essay on the most remarkable note -- well, read it for yourself:

Being an anthropologist only by avocation, I may perhaps venture to claim for anthropology more than most anthropologists dare claim for themselves. The ultimate function of anthropology is no less than to provide the knowledge requisite for the guidance of human evolution (Dobzhansky 1963:148).

Shades of Hari Seldon, to be sure, but especially humorous in light of later events in the field. Still, one wonders how an anthropology directed toward this goal would be organized...

References:

Dobzhansky T. 1963. Anthropology and the natural sciences -- the problem of human evolution. Curr Anthropol 4:138+146-148.

Current Biology is running an interview with biologist and Mutants author Armand Leroi. I found this part interesting:

What important questions remain to be answered in your field? I can think of two. The first is: can we predict the course of organic evolution in the long term? The short term is easy: that's just the breeder's equation. But understanding the longue durée requires a theory that predicts what phenotypes mutation will produce. I am, of course, talking about 'the correlation of parts', 'developmental constraints', 'mutational bias', the 'integration of development with evolution', 'the real reason pigs can't fly' -- every generation since Darwin has considered, and failed to solve, the problem, though they've usually given it a new name.

The second question is rather like the first: can we predict the course of cultural evolution in the long term? (One might add: or even in the short term?) Darwin saw the analogy between cultural and organic evolution; theoretical population geneticists worked out the mathematics of the transmission of cultural traits years ago. Despite this, the field really didn't take off. I think it is taking off now. Culture is the New World of evolutionary science. To be sure, anthropologists discovered it long ago, but rather like Vikings in America, they never made much of what they found.

Well, I suppose nobody ever accused Kroeber of being Hari Seldon, but to anyone knowledgeable in the least about anthropology, this last remark seems a little dippy. Cultural evolutionist theories have come into fashion several times in the last 150 years. The reason that evolutionist ideas tend to go out of fashion is that they really fail to predict any particulars. Now, maybe somebody will find a way to do better, but I'd say any would-be Columbus has some pretty steep problems to overcome.

References:

Leroi, A. 2007. Q & A. Curr Biol 17:R619-R620. doi:10.1016/j.cub.2007.06.006

Ann Gibbons reports on the upcoming article in Current Biology:

[Jill] Pruetz's team, working at the Fongoli research site in the wooded savanna of Senegal, observed chimps breaking off green branches and in four cases using their incisors to sharpen the points. The chimps, which typically weigh 26 to 60 kilograms, were hunting nocturnal bush babies, 100- to 300-gram primates that hide by day in holes in trees. In all, Pruetz and Paco Bertolani, a graduate student at Cambridge University, documented 10 different chimps thrusting the tools into holes in 22 instances. "This is habitual," says Pruetz, whose team logged 2500 hours of observations.

Sucks to be a bush baby.

References:

Gibbons A. 2007. Spear-wielding chimps seen hunting bush babies. Science 315:1063. doi:10.1126/science.315.5815.1063

Here's a LiveScience story by Heather Whipps, about the discovery of chimpanzee nutcracking stones dating back to 4300 years ago:

Though there were no chimpanzee remains at the settlement, testing by archaeologists revealed the tool-laden camp was most likely used by the Great Ape. The stones were much bigger than anything a human could use comfortably and bore the residue of nuts that modern chimpanzees like to snack on.

"This is the only case of any prehistoric, non-human Great Ape tool use ever discovered," [archaeologist Julio] Mercader told LiveScience.

That's very cool. The news piece claims that this is great vindication for the idea that chimpanzees developed this ability without exposure to humans. That is, some people had argued that chimpanzees might have been "acculturated" to crack nuts by watching nearby people. Personally, I never thought there was much to that idea, since nutcracking is so widespread among chimpanzees and clearly learned by chimps with minimal or no human contact.

The most interesting part to me is the possibility that archaeologists will develop a search strategy for stone tools older than flaked stone tool manufacture.

The NY Times writer Benedict Carey has an interesting short article about research into repressed memories. There is a group of researchers who claim that the phenomenon is a cultural construct that emerged very recently:

In a paper posted online in the current issue of the journal Psychological Medicine, a team of psychiatrists and literary scholars reports that it could not find a single account of repressed memory, fictional or not, before the year 1800.

The researchers offered a $1,000 reward last March to anyone who could document such a case in a healthy, lucid person. They posted the challenge in newspapers and on 30 Web sites where the topic might be discussed. None of the responses were convincing, the authors wrote, suggesting that repressed memory is a "culture-bound syndrome" and not a natural process of human memory.

They're saying that the character Madame de Tourvel in Naturally, other researchers dispute the idea -- some even claim to have evidence from ancient Greek literature.

If I have an informed opinion, I've repressed it. But what I find interesting is the idea that a popular literary trends lead scientific research, sometimes to wrong results. It may be hard to rule out that something imagined in fiction could actually happen -- think of the number of people who have tried to find loopholes in special relativity that could lead to faster-than-light travel. There was no science fiction in 1800, but developing ideas about the mind provide their own equivalent.

We know that science can proceed along a false or misleading path for a long time when the cultural biases of the scientists lead research. Fictional plot devices are clever just insofar as people are willing to "suspend disbelief" about them -- which is a function of the readers' cultural biases. So the two combined might make for some interesting history!

It's not here, but at Brainethics, where Martin Skov has written up a short intro to the evolution of aesthetics with a booklist from the recent literature.

Neuroaesthetics can be thought of as a part of a more general study of art and aesthetics as a biological phenomenon. I will follow other proponents of this view (such as Tecumseh Fitch) in calling this broader approach bioaesthetics. The overall goal of bioaesthetics is to answer the three basic biological questions - what?, how?, why? - in regard to aesthetic behaviour in humans: what is art and aesthetics?; how does art and aesthetics spring from the brain?; and why did this cognitive ability evolve in humans? Neuroaesthetics is predominantly concerned with question number 2. In the list that follows below I will also mention a number of books that discuss the other two questions.

If you are one of my students and this area interests you, this is as good a list of recent books on the topic as you will find.

Victoria Horner and colleagues (2006) set up two "diffusion chains" of chimpanzees, to see if a learned task could be transmitted faithfully from one chimp to another for several iterations.

Using a powerful three-group, two-action methodology, we found that alternative methods used to obtain food from a foraging device ("lift door" versus "slide door") were accurately transmitted along two chains of six and five chimpanzees, respectively, such that the last chimpanzee in the chain used the same method as the original trained model. The fidelity of transmission within each chain is remarkable given that several individuals in the no-model control group were able to discover either method by individual exploration. A comparative study with human children revealed similar results. This study is the first to experimentally demonstrate the linear transmission of alternative foraging techniques by non-human primates. Our results show that chimpanzees have a capacity to sustain local traditions across multiple simulated generations (Horner et al. 2006:13878)

Essentially, they trained one individual in each of two chimpanzee groups to open a box with a reward inside -- but there were two ways to open the box, and each of these models was taught a different method. Another chimpanzee was given a period of time, with several trials, to observe one of these models opening the box. Then when the learner acquired the method, another chimp became the learner observing the second. And so on.

They found that the two methods were transmitted essentially intact across as many chimpanzees as they tried, with a couple of limits -- some chimpanzees couldn't be paired as model-learner pairs because they were aggressive toward each other, and some just didn't watch the model and learned the task independently. As the paper notes, these cases are interesting because they present limits on the ability of groups to maintain such traditions:

Side branches occurred in both chains because either the model was unsuccessful/unmotivated (RN in FS1, AM in FS2) or aggression occurred bet ween the model and observer (KT to BO in FS1, CY to VV in FS2). The latter highlights the importance of tolerance and reinforces the hypothesis that opportunities for social learning in the wild may be restricted by the level of tolerance between individuals (50) and that not all individuals within a population may be good models for social learning (51) (Horner et al. 2006:13881).

For me, this study helps to clarify some of the constraints on social learning:

It is not the function of diffusion studies to dissect in depth the underlying mechanisms of transmission, although these must be sophisticated enough to ensure the replication of behavior across the generations. However, some limited inferences are suggested by the contrasts deriving from the three-group design. The no-model control condition indicates that for about half the chimpanzees (and children), opening an object like the Doorian fruit can be said to be within their untutored competence. Therefore, it seems reasonable to assume that half the participants from the diffusion chains would also have been able to open the Doorian fruit in a control condition. Their exclusive use of only one of the two available techniques may represent a form of "canalization" (46), whereby a chimpanzee's potentially limitless exploration of a problem is focused around only a subset of behaviors that they see performed by others. Similarly, it is likely that half of the participants in the chains would have failed the control condition, and hence their behavior suggests a more complex social learning mechanism, such as emulation or imitation (28), but further experiments will be required to establish this (Horner et al. 2006:13881).

Of course this is an artificial situation -- with two possible solutions -- but it suggests several of the balancing factors in the learning and transmission of natural behaviors. Simple things ought to be transmitted very readily. But then, if an adaptive behavior is really that simple, then maybe it should be genetically assimilated. One wonders also whether the chimpanzees who failed to pick up the behavior independently would have ever been able to figure it out, or whether they would just remain oblivious to an adaptive resource in the wild. There is also, after all, a possible reason to be bad at trying new things -- that being, that sometimes new things will kill you.

References:

Horner V, Whiten A, Flynn E, de Waal FBM. 2006. Faithful replication of foraging techniques along cultural transmission chains by chimpanzees and children. Proc Nat Acad Sci USA 103:13878-13883. PNAS online

A recent paper in Cognitive Science by Nuñez and Sweetster has evoked several interesting strains of blog commentary. The paper is about the cognition of time as a function of conceptual metaphor with space.

That's pretty abtruse-sounding, and the Wikipedia entry on conceptual metaphor is fairly informative. The basic idea is that we may understand one class of relationships (a conceptual domain) in terms of the relationships that we know apply to another analogous domain.

All the talk about the new article seems to have come from the attention from a New York Times article, which is imprisoned behind TimesSelect, so I'll quote the interesting Savage Minds post instead:

The New York Times is running an article on a recent article in Cognitive Science by Nunez and Sweetser which demonstrates that Aymara speakers imagine the past to be in front of them and the future behind them -- reversed, in other words, from the spatial metaphors we use in English. The Times article notes "If they are right, this is bigger than anything the 60's tossed up. Is it possible that human concepts of time can vary this much because of language and culture? And what would it be like to think this way? Do I have the rest of my life behind me? And how can I let bygones be bygones if they're right in front of me?" Nunez and Sweetser also makes a to-do about the rarity of this pattern, since, it claims that "so far all documented languages appear to share a spatial metaphor mapping future events onto spatial locations in front of Ego and past events onto locations behind Ego."

The flavor of the SM comment is that cognitive scientists often ignore cultural variability that anthropologists hold as common knowledge:

Cognitive Science produce attention-grabbing headlines much more frequently than anthropologists, and this article is a prime example of how they manage to do so: ignorance.

Have Nunez and Sweetser actually conducted some sort of exhaustive examination of 'all documented languages'? No. In fact their citations reveal that they have examined a grand total of seven: English, Wolof, Chagga, Chinese, Japanese, Turkish, and American Sign Language (to be fair one of the articles they site has 'more cross cultural data').

If Nunez and Sweetser had looked a little bit further -- for example to the Pacific -- they would have found that these sorts of metaphors are quite common.

After the original post, there is a discussion in the comments at Savage Minds with links to elsewhere, including a Language Log entry on the paper:

I feel a need to address recent controversy regarding the uniqueness of the Aymara conceptualization of time-as-space. I cannot respond to everyone who says that their language of choice also has a "back to the future" metaphor, nor will I attempt to reconstruct all of the linguistic (metaphor-based) arguments involved. However, many of the objections that I have heard (and that I am sure the researchers of Aymara asked themselves) are based on a misconception that if a language has a single word that is polysemous between "front/past" or "back/future", then it automatically makes Aymara non-unique.

The short post then discusses why the Aymara case may be different from many others, which centers on the use of gesture as another communicative mode that redundantly includes the front:back::past:future axis.

Chris at Mixing Memory gives some commentary on the entire subject:

I've said it before, and I'll say it again: conceptual metaphor theory sucks. Why does it suck? Well, because there's no experimental evidence for it (and plenty of evidence against it). Except, that is, in one domain: time. Specifically, the work of Lera Boroditsky, along with Dedre Gentner and her colleagues, has provided interesting demonstrations of the influence of the way we talk about space on the way we conceptualize time. I've talked about their work before, and now Dave's talking about Gentner's work over at Cognitive Daily, so I won't go into a lot of detail. Instead, I'll give you an idea of what's going on with the time-space metaphors in their work, and then discuss some recent work by Rafael Nu–ez and his colleagues which introduces new types of time-space metaphors. The conclusion generally drawn from this work is that time is conceptualized metaphorically through mappings onto space. At the end of this post, I'm going to argue that no current evidence actually supports that position.

The critique involves the troublesome problems of irrelevant meanings and priming effects -- essentially, although languages may be constructed by applying metaphoric meanings to words, there is little evidence that the mind constructs concepts using these metaphors, and testing the cognitive treatment is very difficult considering the linguistic entanglements.

I don't particularly have any opinion, but it has been interesting reading much of these exchanges, which illuminate one present-day aspect of the Sapir-Whorf language-shaping-cognition paradigm.

References:

Nuñez RE, Sweetser E. 2006. With the future behind them: Convergent evidence from Aymara language and gesture in the crosslinguistic comparison of spatial construals of time. Cognitive Science 30:1-49. Abstract

Nutcracking by capuchin monkeys has become the best non-hominoid example of tool use, and serves as a marker of the potential for anthropoids to develop and maintain cultures. This kind of tool use -- to extract hard-to-get food from mechanical defenses like shells or burrows -- is called extractive foraging.

For capuchins, this kind of extractive foraging allows them to exist in habitat where easier-to-get resources are limited for parts of the year. It is, in other words, a cultural tradition with immediate adaptive value. So exactly how capuchins learn to do this is pretty important.

Ottoni and colleagues (2005) observed the ways that young capuchins acquire information relevant to tool use. The abstract:

The present work is part of a decade-long study on the spontaneous use of stones for cracking hard-shelled nuts by a semi-free-ranging group of brown capuchin monkeys (Cebus apella). Nutcracking events are frequently watched by other individuals - usually younger, less proficient, and that are well tolerated to the point of some scrounging being allowed by the nutcracker. Here we report findings showing that the choice of observational targets is an active, non-random process, and that observers seem to have some understanding of the relative proficiency of their group mates, preferentially watching the more skilled nutcrackers, which enhances not only scrounging payoffs, but also social learning opportunities.

This might seem obvious -- that is, if you want to learn how to crack nuts, then you ought to watch somebody who really knows how to do it. But in terms of time investment it is a bit unusual -- these young capuchins spend a lot of time playing with other young individuals who aren't the best nutcrackers. The research found that scrounging for scraps was one good reason to watch a good nutcracker:

These results point to an active choice of observational targets, strongly suggesting that the nutcracking proficiency of the potential targets is taken into account by the observers. A motivation to learn from a more skilled conspecific does not necessarily have to be a causal factor in the active choice of the target: besides plain social interest and the attractive nature of a noisy activity, another, a more immediate motive -- scrounging -- can provide a parsimonious explanation for the proximate causation of selective observation of nutcrackers (although it can certainly contribute to learning as a side effect). But in this case, the proficiency of the target is even more clearly at issue, since the choice of the most proficient nutcrackers as observational targets would tend to yield, on average, the highest scrounging payoffs.

And it is significant for the transmission of tool use that proficient nutcrackers tolerate this kind of scrounging:

This capuchin group is, most of the time, a relatively relaxed society (Ferreira 2003), where younger individuals are highly tolerated. During the conspecific nutcracking observation and scrounging episodes reported here, no events of antagonism were registered.

So the basic idea is that young capuchins have an ability to "pick out" good toolmakers for observation. The authors relate this ability to "triadic awareness" -- the ability to understand features of a relationship among two other individuals:

Evidence of the sort of triadic awareness implied by an animals capacity of understanding some features of the relationship between two group mates has been experimentally provided by studies of Old World monkeys (Dasser 1988; Cheney and Seyfarth 1990; Silk 1999). Among New World species, Perry et al. (2004) showed that white-faced capuchins (Cebus capucinus) seemed to exhibit triadic awareness, since they tended to solicit coalition partners not only dominant to their opponents, but also with better relationships with themselves than with those opponents.

Our results strongly suggest that capuchin monkeys are capable of discriminating group mates according to their tool-using skills -- being more prone to watch more proficient nutcrackers. In this particular case, scrounging and social learning are not necessarily conflicting tactics, since both are best served by a watch-the-most-successful strategy (Laland 2004). These preferences result in a sort of prestige hierarchy -- distinct and independent of dominance -- such as proposed by Henrich and Gil-White (2001) as a key feature in the optimization of human cultural transmission. Whether the decision-making process involves an actual understanding of relative proficiency ranking or stems out of simple differential associative or reinforcement histories connected with each individual Target, remains to be verified -- but whatever be the underlying cognitive mechanism, this capability can play a decisive role in the establishment of tool use as a behavioural tradition.

Of course, this "triadic awareness" is precisely the kind of logical information that Bateson is attempting to characterize -- features of a relationship emerge from the interaction between two individuals and cannot necessarily be abstracted from knowledge of the individuals alone. (Ah-ha! Now, all this Bateson-quoting starts to make sense....)

A dominance hierarchy can spontaneously emerge just as a function of dyadic relations. No individual needs to know his or her exact place in such a hierarchy, he or she need only know the outcome of interactions with other individuals for the hierarchy to have force.

Triadic awareness allows more interesting strategizing, as pointed out above. It is certainly a desirable trait for individuals who can form coalitions, although it may not be necessary if coalitions are generally formed in opposition to top-ranking (alpha) individuals -- it shouldn't take triadic awareness for non-alpha individuals to coordinate their actions to depose an alpha.

But such awareness certainly should be necessary for a prestige hierarchy. At a minimum, observers of a prestige hierarchy must be able to assess the interactions of other individuals with objects -- exactly who is having some success cracking nuts, for example. That "awareness" consists of a prediction of the typical outcome of interactions -- that is, when you hear individual X cracking nuts, you know that a lot of nut fragments are going to be flying around him. But the prediction based on the interaction is attributed to the individual.

Attributing social qualities to individuals may be a bit more difficult than this -- because the interactions are more complex, and are products of two individuals instead of one -- but they may be of a similar logical type.

References:

Ottoni EB, de Resende BD, Izar P. 2005. Watching the best nutcrackers: What capuchin monkeys (Cebus apella) know about others' tool-using abilities. Anim Cogn 24:215-219. DOI link

In another post I discussed a paper by Dominique Lestel concerning animal cultures. Lestel closes with this sentiment:

I would like to end on a personal note: one thing has always struck me in the organization of the most remarkable utopias of Western literature, and that is the total absence of animals (Lestel 2002:62).

I guess he doesn't mean Dinotopia...

In any event, I also find that interesting. The one exception I can think of offhand is the "Gaia" planet in Asimov's Foundation series, which is pretty explicitly organized along biosemiotic lines, although with the addition of some kind of "superphysical" element (even inanimate objects like mountains are capable of contributing to the "planet-mind" in this utopia). And that makes a strong contrast to the Foundation, which is entirely organized along rational lines, and doesn't -- as far as I can recall -- have any mention of animals.

I'd be interested to make a list of others, if anybody can think of any.

References:

Lestel D. 2002. The biosemiotics and phylogenesis of culture. Soc Sci Information 41:35-68. Abstract

I have been reading an interesting article from 2002 by Dominique Lestel, considering the definition of culture and its applicability to animals. The focus is on communications through signs (i.e., semiotics). From the abstract:

The question of animal cultures has once again become a subject of debate in ethology, and is now one of its most active and problematic areas. One surprising feature of this research, however, is the lack of attention paid to the communications that go in in these complex animal societies, with the exception of mechanisms of social learning. This neglect of communications is all the more troubling because many ethologists are unwilling to acknowledge that animals have cultures precisely because they do not possess language, a refusal therefore on semiotic grounds. In the present article, I show that the biosemiotic approach to animal cultures is, on the contrary, essential to their understanding, even if the complexity of animal communications is far from being well enough understood....

The paper starts with a fair review of evidences of "cultures" in animal species, including primates, birds, and cetaceans, and notes that these are often diagnosed by the existence of intergroup variability, deceit, or -- in the case of communication -- apparent syntactic structure or referential content.

One problem studying communication is this:

It is hard to investigate the differences and similarities between animal communications and language from the simple standpoint of continuity or discontinuity. It is not trivial to find a feature of human language which is not found to some degree in the communications of at least one animal species, even though language remains the only system of communication which possesses all of these features at once (Snowden 1999). Yet this kind of comparison is not really satisfying, as it takes language too exclusively as the standard for all other semiotic systems. Language and animal communications differ in a host of significant ways, some of which are altogether unexpected, such as the physical duration of the vocal expressions in animals. Birds rarely sing sequences lasting longer than 15 seconds. And these are rare. Most birds do not exceed six seconds, and the average hovers around three seconds, as in most parrots. Only humans and humpbacked whales have non-repeated sequences which last longer (Hartshorne 1973).

The "productivity" of human language is often considered to set it apart from animal communications -- language can be used to express an arbitrary range of concepts and these can be combined into arbitrarily long utterances. Animal vocal communication starts out with a huge handicap in this regard, since it is strictly limited to very short utterances.

The bee prophecies

I couldn't resist that heading after reading this passage:

Haldane (1953), far from immediately focusing on the differences and similarities between the "language" of bees and human language, asked himself what distinguishes and what links an action and a communication. In the hive, bees undeniably make movements which elicit responses in other bees; but the first are not necessarily communicating information about the new food source. Some of these movements can be regarded as ways of expressing the next action. Haldane came to the logical conclusion that the distinction between communication and action is not as clear as it had seemed. Not only can animals express movements indicating intention, they can also reply to them. The more ritualized the movements, the easier it is to reply. Haldane therefore suggested that, rather than being the communication of a message, the bee dance was a highly ritualized movement of intention which took place before leaving the hive and which caused any other bee to leave in a like manner. The honey-bee's dance can thus be interpreted as the prediction of its future movements ratehr than the description of its past movements. Haldane considered that the bee dances were interesting because of their "temporal ambiguity", which makes them both prophecies and stories (Lestel 2002:45-46).

I find this idea interesting for two reasons. First, it seems applicable to some of the ritualized communications in primates, such as threat displays. Clearly these are not "accounts" of past or present irritation, they are iconic predictions of near-term aggression. They use characteristic facial expressions, movements, and vocalizations, and the intensity and duration of these elements roughly predicts the likelihood that aggression will follow. But to a much greater extent than the bees, other primate individuals can respond to threat displays and possibly avert violence through their own submissive or reconciliatory actions.

Second, it suggests an alternative for a hypothesis I've never much liked -- the hypothesis that archaic humans didn't have a concept of the future. Upper Paleolithic Europeans made storage pits for food, they exploited seasonal food sources like salmon runs and reindeer migrations, and they traded and curated objects across long distances. All these things suggest that they could think in ways that enabled planning for different future conditions. Earlier humans did not do these things, leading to the hypothesis that they were incapable of this kind of planning. The idea of planning has also been carried over to raw material utilization, which becomes more intensive and standardized in later people. So some have suggested that Neandertals and other archaic humans did not have a clear conception of the future, or an ability to plan their pattern of activities to deal with seasonal fluctuations and longer-term changes.

But the animal communication analogy indicates that at least short-term future actions are accessible not only to the individual, but are potentially communicated to others as well. One might even say there is no purpose to communication if the probabilities of future events were not to some extent incorporated in it. Organisms communicate in order to increase their own fitness by altering the behavior of others. Nonlinguistic communications take on the flavor of a poker game, in which successive acts may increase or reduce the likelihood of certain outcomes.

The act of communication itself implies a prediction of the future -- and that is in the absence of language. Linguistic communication gives an even greater potential for creating a real conception of the present and the past -- conditions distant in space and time from the individual may be made known through language.

It would seem that behavior must be to some extent ritualized to serve as a sign, so that it can be recognized as bearing intentional meaning. Even so, one need not be all that precise -- and perhaps the exaggerated form of many threat displays is a way of ensuring the proper interpretation even with a lot of noise in the reception system.

Two questions can be posed at this stage. First, would human societies have developed in the same way in a space without animals?

I would expand this question to consider not only domesticated or semi-domesticated animals like dogs, but also wild animals -- building off the fact that early humans had to read the signs and thereby understand and predict the behavior of wild animals in order to eat. There has long been a strain of prehistoric archaeology that has examined the fact that many hunter-gatherers conceptualize animal behavior in explicitly cultural terms. Thus, they conceive of animal "obligations" and "gifts", and

And second, what place do human societies assign animals in their organizations? This is one of the major questions glossed over in our approach to human societies. With the rise of biotechnologies and the heated discussions on animal rights, on the legitimacy of industrial farming and on protecting biodiversity, these have become burning questions (Lestel 2002:62).

This appears to be more sympathetic than I am to the idea that the cognitive adaptations of some animals should merit special "rights" of some kind. But certainly that movement has arisen within the context of a human society that increasingly incorporates animals into intimate social groups.

References:

Lestel D. 2002. The biosemiotics and phylogenesis of culture. Soc Sci Information 41:35-68. Abstract

An interesting story from Howard Hughes Medical Institute (via Science Blog) about the information content of whale song. They don't know what the whales are communicating, but they can assess the number of bits transmitted:

[HHMI predoctoral fellow Ryuji] Suzuki said that information theory also enabled the researchers to determine how much information can be conveyed in a whale song. Despite the "human-like" use of hierarchical syntax to communicate, Suzuki and his colleagues found that whale songs convey less than one bit of information per second. By comparison, humans speaking English generate 10 bits of information for each word spoken. "Although whale song is nothing like human language, I wouldn't be surprised if some marine mammals have the ability to communicate in a complex way," said Suzuki. "Given that the underwater environment is very different from our world, it is not surprising that they would communicate in rather a different way from land mammals."

There seems to be much emphasis on the "hierarchical" aspect of the songs, and this is important -- a single call is made up of many smaller subunits, each of which may carry information content and the arrangement of them may itself carry information content.

Suzuki, who began the project as an electrical engineering undergraduate at the University of Massachusetts, Dartmouth, worked with Buck and Tyack to develop a computer program to break down the elements of the whale's song and assign an abstract symbol to each of those elements. Suzuki wanted to see if he could design a computer program that enabled scientists to classify the structure of the whales' songs.

He used the program to analyze structural characteristics of the humpback songs recorded in Hawaii. To measure a song's complexity, Suzuki analyzed the average amount of information conveyed per symbol. He then asked human observers who had no previous knowledge of the structure of the whale songs to classify them in terms of complexity, redundancy, and predictability. The computer-generated model and the human observers agreed that the songs are hierarchical, confirming a theory first proposed by biologists Roger Payne and Scott McVay in 1971.

...

The structure of the humpback whale song is repetitive and rigid. The whales repeat unique phrases made up of short and long segments to craft a song. There are multiple layers, or scales, of repetition, denoted as periodicities. One scale is made up of six units, while a longer one consists of 180-400 units. The combined periodicities give the song its hierarchical structure.

A hierarchical format is vastly more learnable than any nonhierarchical alternative capable of encoding an equivalent amount of information, so it should not be surprising that this structure would have arisen in another highly communicative species. It emphasizes that limits on information transfer are just as fundamental to the evolution of social intelligence as limits on optics are to visual perception.

George Will's Newsweek column is about football this week -- specifically a discussion of changes in the sport since the days of the late "Bear" Bryant.

He gave some facts about change in player weight that surprised me:

Also in the 1960s, unlimited substitution began making huge players practical as offensive or defensive specialists. Barra notes that Bryant's 1966 team "looked like an average high school team today." It went 11-0 and then won the Sugar Bowl. It had only 14 players who weighed more than 200 pounds. The two heaviest weighed 213. The linemen averaged 195. The quarterback weighed 175.

Today, Scouts, Inc., reports that nearly 40 percent of the interior linemen who will go to Division I colleges in September 2006 -- many of these players not yet 18 -- already weigh at least 300 pounds. In 1980, only one NFL player topped 300. In 1994, the year a mortality study found that linemen have a 52 percent greater risk of dying from cardiovascular disease than the general population and that the largest players have six times the risk of cardiac death than normal-size players, the number of 300-pounders was 155. Ten years later 370 NFL players exceeded 300, and 10 exceeded 350.

This season, the offensive lines of 30 of the 32 NFL teams average at least 300 pounds, and one team averages 323. Of the 61 offensive college linemen invited to last February's NFL Scouting Combine, 58 weighed at least 300. Of the three little fellows, one weighed 299 and two weighed 298.

Of course, other players are getting bigger too -- even quarterbacks. But the change in offensive linemen is remarkable. An interesting case of a sudden shift in the conditions of existence, followed by gradual evolution to fill an new niche.

Carl Zimmer has an article in Forbes covering recent experiments in chimpanzee vocal communication.

But don't write off those grunts and hoots just yet, at least according to a new study that appears in the Oct. 15 issue of the journal Current Biology. Katie Slocombe and Kaus Zuberbuhler, two primatologists at the University of St. Andrews in Scotland, investigated a particular noise chimpanzees make when they find food, called a "rough grunt." At the Edinburgh Zoo, the scientists fed the chimpanzees two different foods--apples and bread--and recorded the sounds they made. Chimpanzees prefer bread to apples, and Slocombe and Zuberbuhler discovered a corresponding difference in the rough grunts they made for each food. They hit a distinctively high note when they came across the bread, and but made lower and noisier grunts for apples.

It's a short article, supplemented by an entry on the Loom.

This online issue of Forbes

There are a number of short interview excerpts in the issue. One has Noam Chomsky discussing spontaneous language innovation in deaf communities. Another from Jane Goodall on the perils of e-mail communication:

I remember when I worked for Lewis [sic] Leakey, first as his secretary. He was very impulsive. He'd get a letter in the mail, and he would open it, and it would be perhaps something from a scientist he thought was quite ridiculous. You could hear him muttering "Bosh! Rubbish!" The poor bit of paper would be scored with his marks, and he'd turn to me and say "Get so and so on the phone!" I got very wise to his moods, so I would pretend the number was engaged, or the man wasn't there, and then an hour or two later, he was rational again.

And other interviews and articles, with Arthur C. Clarke, Wil Wheaton, Desmond Morris, Steven Pinker and many others. Many thanks to the reader who pointed me to the site.

Reuters is reporting on a current study by Joan Silk and colleagues in Nature.

Here's the intro:

Chimpanzees share many traits with humans but altruism, it seems, is not one of them, scientists said on Wednesday.

Although chimps live in social groups and co-operate and hunt together, when it comes to helping non-related group members, they don't put up with any monkey business.

When given the opportunity to help themselves and other chimps they often choose the selfish option.

The experimental setup gave the subject an option between two alternatives:

If the subject (hereafter referred to as the actor) chose option 1, the actor obtained a food reward and another chimpanzee simultaneously received an identical reward (hereafter referred to as the '1/1 option'). If the actor chose option 2, the actor obtained the same size and type of food reward, but no food reward was delivered to the other chimpanzee (the '1/0 option'). As a control, actors were presented with exactly the same reward options when there was no other chimpanzee present (Silk et al. 2005:1357).

So it's not a benefit/cost comparison, but a benefit/benefit. Sort of like if you won a house party from VH1, and you could either decide to invite other people or have the party all to yourself.

The chimpanzees didn't choose the "1/1 option" any more often when another chimpanzee was there (and got the reward) than when there was no other chimpanzee there. Those unfeeling primates!

I'm of two minds about the study. On the one hand, I'm not entirely sure how untutored humans would perform on this one. I think my two-year-old twins would pass -- when we are giving out treats, one will insist on an extra treat to bring to her sister. That situation is pretty analogous to the experiment, I think -- it's not like there's any cost to asking for an extra, since we know they are going to take it to the other twin. Nor is it really analogous to "sharing", which they do inconsistently. But we've had to work pretty hard to teach them to give out treats in that way, and they get direct feedback from us and the grateful sibling.

Considering how complex even this simple case is, I'm not too surprised that the chimpanzees would fail to give out the treats to their groupmates. Nobody has taught them how to do it, and there is relatively little direct feedback (although at one study site, the potential recipients sometimes made begging gestures). And I don't think that untutored humans would do it without explanation and feedback -- it's just that humans have a pretty sophisticated verbal and nonverbal ability to give that kind of feedback. So there is a genuine cognitive difference between humans and chimpanzees that may be involved in the result, although it is not perfectly clear that it is "indifference" in the chimpanzees.

On the other hand, look at the claim at the end of the paper:

These results complement observational and experimental studies that indicate that chimpanzees cooperate mainly with kin and reciprocating partners and show no aversion to inequitable exchanges that benefit themselves (Silk et al. 2005:1358).

This raises a question: would chimpanzees give out the treat to their kin? If not, then we're not seeing a failure to be empathetic toward the "unrelated other", we're seeing a failure to be empathetic at all. But we know that chimpanzees do behave preferentially toward kin in many contexts. So if this test failed to show empathy toward kin, it would be a failure of the test, and not a real indication of chimpanzee behavioral capacities.

So I think there are some missing steps here. Coming up with clear psychological demonstrations of the concept of empathy, or altruism, or welfare of other individuals is tough.

References:

Silk JB et al. 2005. Chimpanzees are indifferent to the welfare of unrelated group members. Nature 437:1357-1359. Full text (subscription)