Intelligence: Darwin vs. Wallace

It’s Charles Darwin’s birthday today! He’s 202. So in celebration I’ve written a post on the still ongoing controversy which the theory of evolution by natural selection caused and is causing, specifically with regards to the emergence of human intelligence.

Alfred Russel Wallace is widely seen as the co-discoverer of the theory of evolution by natural selection. While Darwin had been formulating his theory from as early as the late 1830s, he kept quite about it for more than twenty years while he amassed evidence to support it. In 1858 Alfred Russell Wallace, a naturalist of the same time, sent Darwin a letter outlining for him a theory of evolution which very closely mirrored Darwin’s own. The pair co-presented their theory to the Linnaean Society in 1858 but due to Darwin’s long time amassing evidence and refining his ideas, it was his book, On The Origin of Species, which was published in 1859 and set Darwin’s name firmly in the history books as the discoverer of natural selection.

While Wallace’s part in the discovery of natural selection is far from undocumented or unknown, it is largely for presenting ‘the same ideas’ as Darwin for which he is known and what is rarely discussed in the differences in their ideas. In this post I will briefly discuss a new(ish) paper by Steven Pinker on the evolution of human intelligence and some the differences between the thinking of Darwin and Wallace on the subject.

Darwin, unsurprisingly, asserted that the abstract nature of human intelligence can be fully explained by natural selection. In opposition to this Wallace claimed that it was of no use to ancestral humans and therefore could only be explained by intelligent design:

“Natural selection could only have endowed savage man with a brain a few degrees superior to that of an ape, whereas he actually possesses one very little inferior to that of a philosopher.”(Wallace, 1870:343)

Unsurprisingly most scientists these days do not agree with Wallace on either the point that the human brain could not be the result of natural selection or that as a result of this problem it must have been a product of design by a higher being. It would be both dismissive and dull to leave the discussion at that however, which is where Pinker comes in. Despite Wallace’s argument probably coming to the wrong conclusion he does bring up some very interesting questions which need answering, namely that of; “why do humans have the ability to pursue abstract intellectual feats such as science, mathematics, philosophy, and law, given that opportunities to exercise these talents did not exist in the foraging lifestyle in which humans evolved and would not have parlayed themselves into advantages in survival and reproduction even if they did?” (Pinker, 2010:8993)

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

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

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

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

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

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

taken from Call & Tomasello 2008

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Prairie Dog Communication

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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Erro Replicado

Replicated Typo is, as the name suggests, interested in transmission and change of cultural phenomena.  I’m also particularly interested in bilingualism.  That’s why I have to point out my recent discovery at Cognição, Linguagem e Música: A post by me, in Portuguese.

Well, more accurately, Pedro Lourenço Gomes has translated one of my recent articles.  It’s fascinating that some of my thoughts may reach people with whom I could not communicate directly.  Here’s an extract:

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

Translation: Há uma batalha prestes a começar. Uma batalha no mundo da modelagem cognitiva. Ou pelo menos uma escaramuça. Dois artigos a serem publicados na Trends in Cognitive Sciences debatem os méritos de abordar a cognição a partir de lados diferentes do microscópio.

Just for comparison, here’s the original run through Google translate : Há uma batalha prestes a começar. Uma batalha no mundo da modelagem cognitiva. Ou pelo menos um pouco de uma escaramuça. Dois artigos que serão publicados no Trends in Cognitive Sciences debate o mérito de abordar a cognição de lados diferentes do microscópio.

Actually, it looks like Google translate has done an OK job, although I don’t know anything about Portuguese.  I had a look for more translations of Replicated Typo posts by searching for “Replicated Typo” with various language filters.  Alas, I could find nothing.

Cognição, Linguagem e Música looks like a great blog with reviews of books and articles and lots of posts about music.

Language, Thought, and Space (V): Comparing Different Species As I’ve talked about in my last posts (see I, II, III, and IV) different cultures employ different coordinate systems or Frames of References (FoR) when talking about space.  FoRs

“serve to specify the directional relationships between objects in space, in reference to a shared referential anchor” (Haun et al. 2006: 17568)

As shown in my last post these linguistic differences seem to reflect certain cognitive differences:

Whether speakers mainly use a relative, ego-based FoR, a cardinal-direction/or landmark-based absolute FoR, or an object-based, intrinsic based FoR, also influences how they solve and conceptualise spatial tasks.

In my last post I also posed the question whether there is a cognitive “default setting” that we and the other great apes inherited from our last common ancestor that is only later overridden by cultural factors. The  crucial question then is which Frame of Reference might be the default one.

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Language, Thought and Space (III): Frames of Reference in Language and Cognition

In the second chapter of his 2003 book Space in Language and Cognition: Explorations in Cognitive Diversity, Stephen Levinson discusses a concept that has been crucial to discussions of space and ‘perspectivation’ in language: frames of reference. (see e.g. these posts on my blog Shared Symbolic Storage) The term as it is used today was coined by Gestalt theorists of perception in the 1920s and was used to signify the steady and constant background against which other objects could be made out and identified. It can be defined as
“‘a unit or organization of units that collectively serve to identify a coordinate system with respect to which certain properties of objects, including the phenomenal self, are gauged’ (Rock 1992: 404, emphasis in Levinson 2003: 24).

Language, Thought, and Space (II): Universals and Variation

Spatial orientation is crucial when we try to navigate the world around us. It is a fundamental domain of human experience and depends on a wide array of cognitive capacities and integrated neural subsystems. What is most important for spatial cognition however, are the frames of references we use to locate and classify ourselves, others, objects, and events.

Often, we define a landmark (say ourselves, or a tree, or the telly) and then define an object’s location in relation to this landmark (the mouse is to my right, the bike lies left of the tree, my keys have fallen behind the telly). But as it turns out, many languages are not able to express a coordinate system with the meaning of the English expression “left of.” Instead, they employ a compass-like system of orientation.

They do not use a relative frame of reference, like in the English “the cat is behind the truck” but instead use an absolute frame of reference that can be illustrated in English by sentences such as “the cat is north of the truck.” (Levinson 2003: 3). This may seem exotic for us, but for many languages it is the dominant – although often not the only – way of locating things in space.

What cognitive consequences follow from this?

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Language, Thought and Space (I): Lumpers and Splitters

There have been some very interesting discussions of the relationship between language and thought recently, including for example, Sean’s absolutely fascinating series of posts about the evolution of colour terms,  a great post on descriptions of motion in different languages over at the lousy linguist (here), Guy Deutscher’s article “Does Your Language Shape How You Think?” (for discussions, see e.h. here and here), a slightly less recent piece by Lera Boroditsky in the Wall Street Journal, and an excellent recent discussion of her article by Mark Liberman (here). (see also James’ post, including a great/terrible joke about Whorf).

One of the things that Deutscher wrote in his article was that:

“The area where the most striking evidence for the influence of language on thought has come to light is the language of space — how we describe the orientation of the world around us.”

As I’ve written a bit about this topic on my other blog, Shared Symbolic Storage, I’ll repost a short series of posts over the next couple of days.
As Deutscher said, this is a very fascinating avenue of linguistic research that gives much insight into the nature of language and cognition as well as their relationship. In addition, it also presents us with new facts and considerations we have to take into account when we think about how language and cognition evolved.

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Evolution of Colour Terms: 6 Categorisation Constraints

Continuing my series on the Evolution of Colour terms, this post reviews evidence for categorisation constraints on colour perception. For the full dissertation and for references, go here.

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