How do ideas spread?

spread of language on twitter

Cultural transmission is something I’ve written about before. An arXiv paper has a clever way of studying it on twitter: follow the creation of electronic language.

For example, the abbreviation ikr, meaning “I know, right?” occurs six times more frequently in the Detroit area than in the US overall; the phonetic spelling suttin, meaning “something”, occurs five times more frequently in New York City; and the emoticon^-^, meaning nervous or shy and of Korean origin, is four times more common in Southern California.

At the beginning of the study, the abbreviation ctfu, which stands forcracking the fuck up or laughing, appeared mainly in the Cleveland area but by 2012 was being used in Pennsylvania and the mid-Atlantic. However, ctfu is rare in the large cities to the west of Cleveland, such as Detroit and Chicago.

But the team also say that new words tend to be shared between metropolitan areas that have a similar racial mix. In fact, the proportion of African-Americans as the strongest predictor of similar usage. “Examples of linguistically linked city pairs that are geographically distant but demographically similar include Washington D.C. and New Orleans (high proportions of African-Americans), Los Angeles and Miami (high proportions of Hispanics), and Boston and Seattle (relatively few minorities, compared with other large cities),” say Einstein and pals.

On twitter, does the racial mix of two cities predict the likelihood of irl (see what I did there) friends/family? Or is it, thanks to the internet, more about the connection of people with similar interests/culture?

(ht freakonometrics)

Chimps stick grass in their ears to be cool: notes on cultural transmission

grass in ear

1. In 2010, a female chimpanzee named Julie began repeatedly stuffing a stiff blade of grass into her ear. This Grass-in-ear behavior has affectionately been dubbed “GIEB” by the scientists who observed it.

2. Out of a group of twelve chimpanzees, eight engaged in GIEB. In three other groups of chimpanzees found in other locations in the same forest, only one was ever seen to GIEB.

3. The more that an individual associated with Julie, the more likely they were to GIEB.

4. After the inventor of GIEB died – if one could be said to invent a thing like putting grass in one’s ear – two chimpanzees continued to engage in the activity. They were never seen to do it together, let alone put grass in the other one’s ear.

5. A young monkey named Imo once noticed that her sweet potatoes were covered in sand and that if she dunked them in the water they would become clean. Within a few years, every monkey on her island was dunking sweet potatoes. She later learned that if she dunked them in the ocean instead, plunging them in after every bite, they would taste even better. The lesson? Monkeys love seasoned potatoes.

Japanese macaque stone handling

6. Some Japanese macaques like to play with stones, clicking and clacking them, rolling them along their hands, cuddling or pushing or throwing them. This was first invented by a young female monkey named Glance in 1979. Her playmates learned it first, followed by theirs. What began as transmission among friends has transformed into transmission among generations: now babies learn it from their mothers.

7. There are at least 11 mutations of this stone handling behavior, including “Rub With Hands”, “Grasp Walk”, and “Flinting”. These variations appear to be transmitted between tribes of monkeys when males migrate from one to another. Additionally, each generation appears to add complexity as each individual inadvertently contributes some new idea.

8. Monkeys are not the only animals with social transmission of ideas; many other animals do, though it may not necessarily be for the best. When young guppies are learning where to eat, they follow an older fellow to a source of food. Slowly, they learn from the older guppy which route to take to their food. As time goes on, one guppy learns from another and a route is set. However, this can be maladaptive when there is a faster route available: follow the group even if they know there is a quicker way.

9. One can digitize animals and ask how their theoretical equivalents toss around cultural traits. What causes these electronic cultures to die out? Simple: small groups, high mortality, poor transmission, and costly traits. Prestigious traits, or traits with group consensus, die out just as quickly as any other. In other words, a culture held in high esteem is just as mortal as any other.

10. The connections between members of a group aren’t uniformly random. Instead, they tend to form small worlds, where any two members are just a few steps away from each other. Thank you, Kevin Bacon. In any random network, as the set of connections reaches half the number of members, a “percolation” process causes many small groups to begin congealing into one large group. Much can be learned about sociality and culture using these ideas.

11. It is possible to classify social learning mechanisms in ten distinct ways: stimulus enhancement, local enhancement, observational conditioning, social enhancement of food preferences, response facilitation, social facilitation, contextual imitation, production imitation, observational response-stimulus learning, and emulation.

12. A computer tournament revealed that even indiscriminate copying is often better than trial and error learning. Copied individuals will often perform the best available behavior, and the better the behavior the more likely they were to survive. Thus, survival itself made behavior a non-random sample of the best behavior. Individuals were themselves highly useful filters of information waiting to be copied.


Huffman, M., Nahallage, C., & Leca, J. (2008). Cultured Monkeys: Social Learning Cast in Stones Current Directions in Psychological Science, 17 (6), 410-414 DOI: 10.1111/j.1467-8721.2008.00616.x

van Leeuwen, E., Cronin, K., & Haun, D. (2014). A group-specific arbitrary tradition in chimpanzees (Pan troglodytes) Animal Cognition DOI: 10.1007/s10071-014-0766-8

Laland, K., & Williams, K. (1998). Social transmission of maladaptive information in the guppy Behavioral Ecology, 9 (5), 493-499 DOI: 10.1093/beheco/9.5.493

Nunn, C., Thrall, P., Bartz, K., Dasgupta, T., & Boesch, C. (2009). Do transmission mechanisms or social systems drive cultural dynamics in socially structured populations? Animal Behaviour, 77 (6), 1515-1524 DOI: 10.1016/j.anbehav.2009.02.023

Stocker R, Green DG, & Newth D (2001). Consensus and cohesion in simulated social networks Journal of Artificial Societies and Social Simulation, 4 (4)

Rendell L, Fogarty L, Hoppitt WJ, Morgan TJ, Webster MM, & Laland KN (2011). Cognitive culture: theoretical and empirical insights into social learning strategies. Trends in cognitive sciences, 15 (2), 68-76 PMID: 21215677

What is social behavior, and how has that changed?

Consider someone praying, alone, in front of an altar.  Is this a social behaviour?  Most psychologists working before 1950, certainly 1920, would probably have answered ‘yes’; the activity is demonstrably being shaped by, and takes the form it does, because of that person’s previous social experiences and group membership.  It seems exceedingly unlikely that someone who had never been immersed in the traditions of the church would find themselves praying at this alter, in this physical position…

If you were to ask experimental social psychologists and neuroscientists the same question today, we would find the opposite answer most frequently given: praying is not a social behaviour.  The reason for this is that, within today’s experimental psychology and neuroscience, the social is characterised by two features.  Firstly, within contemporary thinking, the social refers toobjects of cognition (the things which our cognitions are directed towards) and not forms of cognition (the particular shape of those cognitions).  Cognitions, or behaviours, which are present, or altered, by group membership (such as praying) are not social under this framework.  Instead, a social cognition is simply one related to the understanding of other people in the immediate vicinity…

An exception to the rule that we are inherently social creatures is believed to be found in autism.  As described in the introduction, social abnormally is taken to be a, or even the, primary symptom in autistic spectrum conditions.  At the most general level, I think we can easily show that the description of autism as social disorder is reliant upon the contemporary construction of the social, outlined above.  In psychology’s first sense of the social, where praying is social, individuals with autism are demonstrably able: as noted earlier in this essay, many individuals with autism take part in one of the most significant self-advocacy movements of all time.  People with autism are clearly able to join groups, have their behaviours shaped by membership of those groups, and so forth.  It is only when the social is understood as being related to interpersonal conduct that autism becomes conceivable as social disorder residing within an individual who has difficulty with, for example, feeling empathy.

A fantastic essay on the intersection of our ideas of sociality, how those ideas have changed, and autism.

What are scientists? (Hint: we are liars.)

I thought that this was funny:

I figured I could try some other variations:

Apparently, inquiring minds want to know: are researchers working on herpes?


Transmitting behavior between groups

Crowds chanting in unison, wolves hunting in a pack, the superorganism that is the ant colony: these are all things that require the coordination of many individuals to accomplish something that they could not on their own.  And yet, replace any individual with another and the behavior will turn out pretty much the same.  Right?

Let’s look at the example of colonies of harvester ants that forage in the desert for seeds.  These ants adjust their collective foraging behavior through small interactions between individuals: ants decide whether to leave the colony to search for food if they sense other successfully returning foragers.  This way, if a lot of ants are returning with food, more ants will leave because the world is feeling bountiful.  But if few ants are returning with food, fewer new ants will leave to search; it’s just not worth it when there’s not a lot of food out there.  After all, leaving the colony carries a cost.  Every moment in the desert desiccates the poor ant foragers, and if they stay out too long they’ll up and die.

Screen shot 2013-07-17 at 10.30.46 AMAnt colonies don’t forage every day.  Their foraging depends not just on the abundance of food, but on environmental conditions such as heat and humidity.  Beyond this, there are colony-specific traits.  Some colonies will forage every day, some will just forage some days, and this trait persists across years.  This is trait is somewhat transmissible as colonies that reduce their forage on an uncommon day also have daughter colonies that are likely to reduce their foraging on uncommon days. This transmission of collective behavior suggests that responses to environmental conditions can be transmitted from one colony to the next.  This is the human equivalent of a teenager from Scandinavia founding a new town in the midwest and recapitulating parts of his culture there…

It’s not clear what the mechanism here is.  Since daughters of a queen continue to forage in a colony-specific manner, the transmitted component must be unrelated to the genetic contribution of the father.  So is it genetic, and linked to the X chromosome?  Or is it in some sense cultural, learning from the behavior of the greater colony it was raised in?  Hopefully someone who knows more about young ant behavior can enlighten us here…

Either way is interesting.  I can certainly imagine that a dynamic, collective behavior is controlled genetically.  Dopamine receptor expression is linked to foraging behavior, so genetic differences here could easily transmit motivation to forage.  And yet – cultural transmission would be pretty exciting, too.  This would indicate there is some sort of learned component and makes me wonder: if we can measure all the movement of an animal throughout its life, how well could we predict the behavior of a whole group?


Gordon DM (2013). The rewards of restraint in the collective regulation of foraging by harvester ant colonies. Nature, 498 (7452), 91-3 PMID: 23676676

Americans: outliers among outliers

Researchers found that Americans perceive the line with the ends feathered outward (B) as being longer than the line with the arrow tips (A). San foragers of the Kalahari, on the other hand, were more likely to see the lines as they are: equal in length. Subjects from more than a dozen cultures were tested, and Americans were at the far end of the distribution—seeing the illusion more dramatically than all others.

More recently psychologists had challenged the universality of research done in the 1950s by pioneering social psychologist Solomon Asch. Asch had discovered that test subjects were often willing to make incorrect judgments on simple perception tests to conform with group pressure. When the test was performed across 17 societies, however, it turned out that group pressure had a range of influence. Americans were again at the far end of the scale, in this case showing the least tendency to conform to group belief.

It is not just our Western habits and cultural preferences that are different from the rest of the world, it appears. The very way we think about ourselves and others—and even the way we perceive reality—makes us distinct from other humans on the planet, not to mention from the vast majority of our ancestors. Among Westerners, the data showed that Americans were often the most unusual, leading the researchers to conclude that “American participants are exceptional even within the unusual population of Westerners—outliers among outliers.”


Culture and human evolution

Edge has an excellent interview with Joseph Henrich on cultural and biological evolution.  He argues that the distinction between the two is fuzzy; he says they are inseparable but I think what he really means is that we don’t know how to separate them yet.  Although they are distinct concepts, they have feedback on each other which makes the separability difficult-to-impossible (though does not mean they are not distinct!).  To get an example of what he’s saying here:

Another example here is fire and cooking. Richard Wrangham, for example, has argued that fire and cooking have been important selection pressures, but what often gets overlooked in understanding fire and cooking is that they’re culturally transmitted—we’re terrible at making fires actually. We have no innate fire-making ability. But once you got this idea for cooking and making fires to be culturally transmitted, then it created a whole new selection pressure that made our stomachs smaller, our teeth smaller, our gapes or holdings of our mouth smaller, it altered the length of our intestines. It had a whole bunch of downstream effects.

We did not evolve the ability to make fire.  But once we were able to make fire, biological evolution took hold.  Cultural evolution drove biological evolution.  An important point that he makes is that culture and technology can only reach a certain level of richness in any given population level.  More complex societies require larger – or more connected – populations:

I began this investigation by looking at a case study in Tasmania. Tasmania’s an island off the coast of Southern Victoria in Australia and the archeological record is really interesting in Tasmania. Up until about 10,000 years ago, 12,000 years ago, the archeology of Tasmania looks the same as Australia. It seems to be moving along together. It’s getting a bit more complex over time, and then suddenly after 10,000 years ago, it takes a downturn. It becomes less complex.

The ability to make fire is probably lost. Bone tools are lost. Fishing is lost. Boats are probably lost. Meanwhile, things move along just fine back on the continent, so there’s this kind of divergence, and one thing nice about this experiment is that there’s good reason to believe that peoples were genetically the same.

You start out with two genetically well-intermixed peoples. Tasmania’s actually connected to mainland Australia so it’s just a peninsula. Then about 10,000 years ago, the environment changes, it gets warmer and the Bass Strait floods, so this cuts off Tasmania from the rest of Australia, and it’s at that point that they begin to have this technological downturn. You can show that this is the kind of thing you’d expect if societies are like brains in the sense that they store information as a group and that when someone learns, they’re learning from the most successful member, and that information is being passed from different communities, and the larger the population, the more different minds you have working on the problem.

If your number of minds working on the problem gets small enough, you can actually begin to lose information. There’s a steady state level of information that depends on the size of your population and the interconnectedness. It also depends on the innovativeness of your individuals, but that has a relatively small effect compared to the effect of being well interconnected and having a large population.

The analogy between brains and population level is a good one: in the brain, it is not the individual neurons that give rise to complex behavior, but the interactions between them.  The number of neurons determines the complexity of patterns that can be extracted from the environment.  A simple example in computer science is the perceptron; if you have one neuron, you can make a linear decision between two choices.  As you connect more and more neurons, you’re able to increase the complexity of the decision by adding another linear filter; eventually you can be arbitrarily complex, but at low numbers of neurons you’re going to be really limited in the number of patterns that you can decode.

But the level of complexity also has an impact on how we interact with each other:

In the Ultimatum Game, two players are allotted a sum of money, say $100, and the first player can offer a portion of this $100 to the second player who can either accept or reject. If the second player accepts, they get the amount of the money, and the first player gets the remainder. If they reject, both players get zero. Just to give you an example, suppose the money is $100, and the first player offers $10 out of the $100 to the second player. If the second player accepts, he gets the $10 and the first player gets $90. If he rejects, both players go home with zero. If you place yourself in the shoes of the second player, then you should be inclined to accept any amount of money if you just care about making money.

Now, if he offers you zero, you have the choice between zero and zero, so it’s ambiguous what you should do. But assuming it’s a positive amount, so $10, you should accept the $10, go home with $10 and let the other guy go home with $90. But in experiments with undergraduates, Western undergraduates, going back to 1982, behavioral economists find that students give about half, sometimes a little bit less than half, and people are inclined to reject offers below about 30 percent.

…I was thinking that the Machiguenga would be a good test of this, because if they also showed this willingness to reject and to make equal offers, it would really demonstrate the innateness of this finding, because they don’t have any higher level institutions, and it would be hard to make a kind of cultural argument that they were bringing something into the experiment that was causing this behavior.  I went and I did it in 1995 and 1996 there, and what I found amongst the Machiguenga was that they were completely unwilling to reject, and they thought it was silly. Why would anyone ever reject? They would almost explain the subgame perfect equilibrium, the solution that the economists use, back to me by saying, “Well, why would anybody ever reject? You lose money then.” And they made low offers, the modal offer was 15 percent instead of 50, and the mean comes out to be about 25 percent.

We found we were able to explain a lot of the variation in these offers with two variables. One was the degree of market integration. More market-integrated societies offered more, and less market integrated societies offered less. But also, there seemed to be other institutions, institutions of cooperative hunting seemed to influence offers. Societies with more cooperative institutions offered more, and these were independent effects.

This creates a puzzle because typically people think of small-scale kinds of societies, where you study hunter-gatherers and horticultural scattered across the globe (ranging from New Guinea to Siberia to Africa) as being very pro social and cooperative. This is true, but the thing is those are based on local norms for cooperation with kin and local interactions in certain kinds of circumstances. Hunter-gatherers are famous for being great at food sharing, but these norms don’t extend beyond food sharing. They certainly don’t extend to ephemeral or strangers, and to make a large-scale society run you have to shift from investing in your local kin groups and your enduring relationships to being willing to pay to be fair to a stranger.

This is something that is subtle, and what people have trouble grasping is that if you’re going to be fair to a stranger, then you’re taking money away from your family. In the case of these dictator games, in order to give 50 percent to this other unknown person, it meant you were going home with less money, and that meant your family was going to have less money, and your kids would have less money. To observe modern institutions, to not hire your brother-in-law when you get a fancy job or you get elected to an office is to hurt your family. Your brother-in-law doesn’t have a job now. He has to have whatever other job he has, a less good job.