The Extended Mind is an idea in philosophy of mind, that an individual’s mind is not, as might be intuitively assumed, fully contained within the individual’s brain, but in fact includes several aspects of the external world. The Extended Phenotype is an idea in evolutionary biology, that the composite set of an organism’s observable traits (its phenotype) is not, as might be intuitively assumed, fully contained within the organism itself, but in fact includes several aspects of the external world. As can be seen, there is an apparent similarity between these two ideas. Is this similarity only superficial, or is there a deeper relationship?
The Extended Phenotype
Let’s start with the Extended Phenotype. The gloss I gave above of what a phenotype is (“.. the composite set of an organism’s observable traits…”) is not quite right – or at least, it is not precise enough. We should say that something is part of an organism’s phenotype when there is a causal correlation between variation in some part of the genome and variation in the entity itself. For example, some humans have blue eyes, some have brown eyes, and so on and so on – there is variation in human eye colour. At the same time, there is variation in the human genome – and some of this variation correlates with the variation in eye colour. There are genes ‘for’ blue eyes, brown eyes, and the rest.
The Extended Phenotype is Richard Dawkins’ most substantive contribution to evolutionary theory. What Dawkins recognised was that some aspects of the world that are external to the organism just as much satisfy the definition of a phenotype as do eye colour, body shape and all the other aspects of an organism’s form that are more typically thought to constitute its phenotype. The canonical example is the beaver dam: there is causal covariance between dams and the genes for dam building. Beavers with the genes for dam building build dams, and those that don’t, don’t. There are genes ‘for’ dams, and dams are adaptations just as much as are eyes and all the other adaptations that exist within the body. Other examples are plentiful: termite mounds, bird nests, and so on. Once you start looking for them, you realise that extended phenotypes are everywhere.
The Extended Mind
“Where does the mind stop and the rest of the world begin?” It is with this question that the philosophers Andy Clark and David Chalmers launch the idea of the Extended Mind. Clark & Chalmers argue that the limits of the brain are no limit at all, and instead advocate an ‘active externalism’ to the question: the mind includes all those aspects of the world that contribute to cognitive processes.
To illustrate, they introduce a character Otto who, because he suffers from Alzheimer’s disease, must write down everything he knows about the world in a notebook, lest he forget it. As such, Otto’s notebook performs the same role for Otto as your memory does for you. My memory is certainly part of my mind – and so why would Otto’s notebook not be part of his mind? There are differences, to be sure (for example, I access my memory by introspection, Otto does not), but Clark and Chalmers argue that these differences are shallow ones. They write: “To focus on them would be to miss the way in which for Otto, notebook entries play just the sort of role that beliefs play in guiding most people’s lives”. As with the Extended Phenotype, once you embrace the idea, you start seeing it everywhere: the pen & paper I use to do arithmetic; the knot I put in a hankerchief to remind me to phone my mum today; and so on. A funny take on it all comes from the web-comic xkcd:
So what’s the deal?
First things first: the Extended Mind is not an Extended Phenotype of humans. It’s common, when people first come across the idea of the Extended Phenotype, to wonder if all the things humans do to the world (build buildings, dig holes, write their memories in notebooks) are extended phenotypes. Dawkins himself says this is one of the most common questions he receives on the topic. But the answer is no: there is no causal covariance between genes and buildings, or genes and notebooks. There are genes ‘for’ the cognition that enables us to build buildings and write down memories, but there are no genes ‘for’ the buildings or the memories themselves.
So there is no simple relationship or correspondence between the two ideas – and even if there were, that would not be interesting in and of itself. Far more interesting is the common mode of thinking that the two ideas share.
In both cases, the instinctive approach, well represented in both literatures, is to cut nature at the joints: both phenotype and mind end where the environment begins. There is also the radical approach which, crudely put, states that the phenotype and mind, on the one hand, and the environment, on the other, are so deeply intertwined with one another that questions about the limits of each are to some greater or lesser extent ill-posed – and hence that the traditional picture requires re-imagining, or re-building. Clark & Chalmers acknowledge the existence of this school of thought, which they call “externalism about mind”, at the very beginning of their essay. In evolutionary biology this school is represented by, among others, niche construction theory, which argues that contemporary evolutionary theory is simply unable to properly account for the effects that organisms have upon their environments.
It seems to me that the Extended Mind and the Extended Phenotype operate slightly differently from these more revolutionary approaches. They embrace externalism, but not without limits. Both present radical challenges to traditional or instinctive ideas, but they do so in a disciplined way. Not everything is an Extended Phenotype: there are strict conditions that must be met. And although the Extended Mind demands externalism, that externalism is not blind. It is instead an active externalism: what features of the world take part in cognitive processes?
The substantive similarity between the two ideas, then, is not one of the ideas themselves, but one of intellectual discipline. Although both are radical, neither are revolutionary. They are instead just the natural ends of useful ideas: the phenotype is the material expression of the genotype; the mind is what takes part in cognitive processes. Revolutionary ideas generate headlines, but disciplined radicalism is often the better approach.