drghirlanda

Neuroscience, evolution, and culture

Tag Archives: culture

What makes a dog breed popular?

Some time ago I wrote about fashions in dog breeds, pointing out the wild fluctuations in popularity in many breeds. Why do these occur? Owning a dog is a serious commitment in terms of time and money, and it would seem natural to try to acquire a dog that is healthy and with a good temperament. I set to find out whether this is actually the case with my colleagues Alberto Acerbi, Hal Herzog, and James Serpell.

In our new paper Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity, we show that, surprisingly, people do not prefer breeds that are better behaved or healthier. On the contrary, the most popular breeds are the most unhealthy, with a host of genetic defects that are at least partly related to intense selection to adhere to quirky breed standards, and possibly with more behavioral problems such as fear of other dogs, aggressiveness, or separation anxiety. We obtained these results crossing data from the C-BARQ database of dog behavior created by James (the actual data used in our analysis are here), data about dog registrations provided by the American Kennel Club to Hal Herzog (available here), and previously published health data (references 14-17 in the paper).

Thus many people (at least those interested in breed dogs) prefer to acquire a dog that is socially recognized to meet a certain “standard” than a healthy and well behaved dog. If you are unfamiliar with breed standards, I can tell you that they are quite exacting, and to many may appear just pointless. Here is, for example, what the nose of a bulldog is supposed to look like:

The nose should be large, broad and black, its tip set back deeply between the eyes. The distance from bottom of stop, between the eyes, to the tip of nose should be as short as possible and not exceed the length from the tip of nose to the edge of underlip. The nostrils should be wide, large and black, with a well-defined line between them. Any nose other than black is objectionable and a brown or liver-colored nose shall disqualify.

(From the AKC web site)

Note: “disqualify” means that the dog should not be considered a “true bulldog.”

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The age of human cultural capacity

Venus of SchelklingenWhen did humans evolve, to its full extent, the capacity to create complex culture? We consider this question in a paper appearing in the May 7th issue of Scientific ReportsHere is a quick summary.

Human cultural capacity has been traditionally dated to about 30-40 thousands of years ago, based on an impressive cultural explosion in Europe around that time, leaving us such evidence as sophisticated stone tools and plenty of “art” (objects without any clear practical use), like the figurine depicted to the right, the lion man, and striking cave paintings.

There is a problem, though. If cultural capacity evolved in Europe 30-40 thousand years ago, how did all the human groups that where living outside Europe get it? We have no evidence of genetic flow from Europe to the rest of the world, through which the genes responsible for cultural capacity could have spread. It appears that humans must have had the capacity to create complex culture before they fragmented geographically over a large area. This conclusion, however, appears equally problematic because the first split between human populations is currently dated at about 170,000 years ago. Thus humans would have had the capacity for complex culture for more than 100,000 years before complex culture actually appeared. Although this appears unreasonable, we argue that things actually went this way.

First, we note that archaeologists have unearthed stone tools of complexity comparable to that of the European cultural explosion, but much older (more than 200,000 years old). We also note that other indicators of behavioral modernity appeared earlier than 170,000 years ago, such as genes believed to be important for language and the morphology of the speech apparatus.

Second, we summarize recent work in cultural evolutionary theory showing that cultural evolution is, in its initial stages, exceedingly slow. The reason is essentially that culture is a cumulative process: Complex culture can be created only by building on already existing culture. Thus in the initial stages of cultural evolution there was not enough raw material to be elaborated upon, and the creation of culture was slow. Additionally, human groups were at this time small and scattered over a large area, hence it is likely that cultural elements have been invented many times but disappeared (we make a couple of examples in the paper).

The bottom line is that there is no evidence inconsistent with an early origin of cultural capacity, and current understanding of cultural evolution shows that a long gap between the genetic evolution of the capacity and the actual invention is, in fact, quite expected.

And, we suggest in the paper, Neanderthals may have had the same cultural capacity as ourselves.

Empirical support for openness-persuasiveness dynamics

A recent study by Aral & Walker provides support that the openness-persuasiveness dynamics we suggested a few years ago actually goes on in cultural evolution. In short, we had put forward mathematical and simulation models to support the notion that learning from others produces individuals that, over time, become more conservative (less likely to learn from others) and more persuasive (more likely to convince others of one’s own ideas). These predictions have been confirmed by Aral & Walker, who showed that older Facebook users are more difficult to convince do adopt a Facebook app than younger users, and yet are better at convincing others to adopt the app. Up to now, we only had indirect evidence about openness (older people score low on openness in personality tests), and no evidence on persuasion.

We have submitted a comment to the journal relating Aral & Walker’s intriguing findings to our theory. You can find a slightly extended version here, essentially with more references to relevant work.

Human Cognitive Uniqueness conference videos are online!

Watch them here!

Videos and slides for Understanding Human Cognitive Uniqueness

I am starting to post videos and slides from Understanding Human Cognitive Uniqueness on the conference page. They will be uploaded as they get ready.

The videos have been recorded and edited by Malene Schjoenning.

Understanding Human Uniqueness Flyer

We have prepared a flyer to advertise the Conference on Human Cognitive Uniqueness that will take place at Brooklyn College on May 29-30. Feel free to use it to advertise the Conference yourself!

The Logic of Fashion Cycles

As announced a few weeks ago, our paper “The Logic of Fashion Cycles” has been published, and is freely available on the PLoS ONE website. You can find a good summary at The National Post.

New paper: The logic of fashion cycles

Plos ONE has accepted our paper “The logic of fashion cycles,” where Alberto Acerbi, Magnus Enquist and myself present a new theoretical model to understand fashion cycles (see my previous post on dog breeds). You can download a preprint, and here is the abstract:

Many cultural traits exhibit volatile dynamics, commonly dubbed fashions or fads. Here we show that realistic fashion-like dynamics emerge spontaneously if individuals can copy others’ preferences for cultural traits as well as traits themselves. We demonstrate this dynamics in simple mathematical models of the diffusion, and subsequent abandonment, of a single cultural trait which individuals may or may not prefer. We then simulate the coevolution between many cultural traits and the associated preferences, reproducing power-law frequency distributions of cultural traits (most traits are adopted by few individuals for a short time, and very few by many for a long time), as well as correlations between the rate of increase and the rate of decrease of traits (traits that increase rapidly in popularity are also abandoned quickly and vice-versa). We also establish that alternative theories, that fashions result from individuals signaling their social status, or from individuals randomly copying each other, do not satisfactorily reproduce these empirical observations.

Fashions in dog breeds

I have recently attended a one-day course on data visualization with Edward Tufte and I have tried to put his advice on virtual paper in this supergraphic on the popularity of dog breeds, using AKC data (courtesy of Hal Herzog). The graph shows the popularity of 100 breeds over time (most popular breeds first), indicating the maximum in popularity and other peaks (if any). I have produced this graph as an inspiration for my ongoing work on cultural dynamics (some features are idiosyncratic to the data analyses I am making). Here are a few things I see in the graph:

  • Many breeds have had a clear peak of popularity, after which their diffusion declined to low values. This applies especially, but not only, to breeds used purely as pets – such as the all-time favorite, the poodle.
  • The faster a breed rises in popularity, the faster it goes back to its pre-spike level (this is not only a visual impression, it can be put on strong statistical grounds). A similar phenomenon has been observed for first names.

What else can you see? And how to explain it? In am working, with Alberto Acerbi and Magnus Enquist on an explanation of fashion cycles based on the cultural dynamics of preferences, as foreshadowed in our previous work on how social learning influences openness to new information. The paper is now under review at Plos ONE.

Video: Pete Richerson, How Possibly Language Evolved

Part of the Cultural Evolution Seminar Series at Brooklyn College

(Download video, 620 MB)

Abstract: Human language has no close parallels in other systems of animal communication. Yet it is an important part of the cultural adaptation that serves to make humans an exceedingly successful species. Evolutionary scholars have have converged on the idea that the cultural and innate aspects of language were tightly linked in a process of gene-culture coevolution. They differ widely about the details of the process, particularly over the division of labor between genes and culture in the coevolutionary process. Why is language restricted to humans given that communication seems to be so useful? A plausible answer is that language is part of human cooperation. Why did the coevolutionary process come to rest leaving impressive cultural diversity in human languages? A plausible answer is that language diversity functions to limit communication between people who cannot freely trust one another or where even truthful communications from others would result in maladaptive behavior on the part of listeners.

Pete Richerson‘s primary research for many years has focused on the phenomena of cultural transmission of information and the evolutionary phenomena that derive from cultural transmission. He has been especially interested in the trade-offs involved in using other people as a source of information. Even if we imagine that the cultural system of humans has been adaptively optimized by natural selection, maladaptive cultural variants can still evolve. People cannot take advantage of normally adaptive rules like “imitate the successful” without incurring the risk that the appearance of success is a sham behind which lurks a culturally transmissible pathology. Prof. Richerson has investigated such processes with mathematical models, laboratory experiments, and most recently field investigations.