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Mind & Self

Humanity, Metaphor & the Recursive Mind

Brian King wonders what there is about human minds that’s unique to us.

There is a cliché, derived from Aristotle, that ‘man is the rational animal’. While all animals have sensations, appetites and fears, only humans, it is said, have the power to reason. The idea that the human mind is radically different from that of any other animal reigned supreme for over two thousand years. Then it was called into question from the middle of the nineteenth century by naturalistic explanations that emerged with the advent of evolutionary theory, primatology, and eventually neuroscience. The new thinking went, there is a difference between a human mind and, say, the mind of a chimpanzee but it is a difference of degree, not of kind. Is it any more significant than the difference between the mind of a chimpanzee and a baboon? Is there something radically different that humans can do with reason which no other animals can? Are the minds of humans a step change from the minds of our closest living evolutionary relatives, chimpanzees and bonobos?

The gradual process of evolution is sometimes interrupted by sudden jumps, and fossil evidence suggests that such a jump occurred with regard to the human brain. The human cerebral cortex (the outer layer of the brain), and in particular, the frontal lobes or neocortex, developed quite suddenly in evolutionary terms; and it is this part of the brain that seems to be the seat of reason.

Some figures will also support the claim. While an average mouse brain has 75 million neurons, and a chimpanzee’s 7 billion, the average human’s has 86 billion. Also tellingly, in the human brain each neuron has far more dendrites (wires linking neurons) than in other animals’ brains, and therefore a different order of interconnectivity between the brain cells. In human brains there are over 125 trillion synapses (brain cell connections) – more than there are stars in 1,500 galaxies!

The suddenness of this development can be seen by comparing the brain sizes of various early types of hominids. While Australopithecus, 4 million years ago, had an average brain size of about 500cc, in Homo erectus, 1.8 million years ago, the average brain size was just under 1000cc. For Homo sapiens, average adult brain size became its present norm of 1500cc about 200,000 years ago. Nearly all that growth was in the outer layers of the cranium and particularly in the prefrontal cortex, which deals with abstract reasoning, making social/moral choices, empathy, and language. A large proportion of the trillions of synapses operate here.

I want to use these points as a springboard for addressing the question of whether there can be a description of the difference between humans and other animals which preserves the principles of evolution and yet maintains the distinctiveness of humans. To do this I want to look at our brain’s capacity to use metaphors and to think recursively. How are these capacities interconnected? How might they relate to the interconnectivity of our neurons? Finally, how can these explain the higher intelligence and abstract thought of humans in naturalistic, non-spiritual terms.

Time For A Metaphor

Metaphors enable us to see things of one type in terms of things of another type so that our understanding may be improved. For example, the Biblical phrase ‘The Lord is my shepherd’ might enhance the idea of one’s relationship with God. But it has been argued by many (such as George Lakoff and Ian McGilchrist) that metaphors are far more fundamental than that. Metaphors can be used to describe one action in terms of another, for example, ‘he defended his position vigorously and won the debate’ – as though the debate was a battle. Metaphors can also describe one relationship or structure in terms of another. So we talk of ‘the orbit of the electrons around the nucleus of an atom’, as though an atom were a miniature Solar System. In fact, metaphors can be used for expressing any idea in terms of another, and furthermore they are prevalent throughout our verbal lives. Often we do not even realise we are using them. For instance, we may say, “The time is approaching when we need to leave”, as though time were something coming towards us. We also often depict time as a line along which we can move in our imagination, both forwards and back, and it could be that our sense of time past and future is helped by this simple spatial metaphor. Or we may say, “I see what you mean”, as though understanding were a form of sight; or, “I get it”, as though understanding was a form of grasping or holding; or, “I can follow your line of argument”, as though an argument is some kind of path. When reasoning we often seem to utilise some kind of imaginary space. We also tend to see abstract things in tactile or physical ways, such as ‘He hardened his attitude’, as though attitudes were material things; or ‘You need a solid foundation for that argument’, as though arguments were like physical structures. Generally, complex thoughts are more easily communicated in simpler terms. For example, we may refer to ‘the conflict between conservative and revolutionary forces in a political party that might tear it apart’, as though the party was a fragile creature or object being pulled in opposite directions. The metaphor makes the idea of the vulnerability of the political party more clearly understood, and we understand it because of our shared human experiences.

It can be seen then that what everyday (as opposed to poetic) metaphors have in common is describing one thing in terms of something more familiar. And the most familiar things we are acquainted with are simple spatial sense, properties of objects and our bodies, and our feelings. Therefore, sophisticated conceptual thought is rooted in our most common or basic animal perceptions and experiences via metaphor. Lakoff, McGilchrist and others argue – in, for example, Lakoff’s The Neural Theory of Metaphor (2008) – that in this way, metaphors are an essential part of thought. Metaphors enable us to think beyond our immediate experiences and so develop conceptual thought, which is metaphorically derived from our simple physical or bodily experiences, as the above examples suggested. Abstract things can only easily be understood in terms of other things with which we are already familiar. This simple rule means that, ultimately, everything is understood in terms of what is most immediately obvious or intuitive to us.

A possible criticism of this idea is that if our understanding of the world is based on metaphors and models we derive from basic experiences, does this mean that we cannot understand anything radically new or different? If all thinking is based on seeing things in terms of things we already understand, then won’t new discoveries and ideas be in those old established frameworks? Perhaps this is why physicist Richard Feynman said of quantum mechanics that if you think you understand it you don’t understand it. What he possibly meant was that quantum physics is so strange, so detached from our normal experiences of the world, that there are no metaphors or everyday models that could help us understand it. Rather, quantum mechanics is a mathematically-derived theory describing a realm whose behaviours are not like those of our everyday experience.

What has all this to do with neuroscience? Neuroscience has shown that neural connections are established physically when ideas are connected in thought, either causally, logically, or metaphorically. The complexity of our cerebral hemispheres suggests that interconnectivity is key to our great ability to understand the world – that is, our ability to depict complex things in terms we are familiar with, using metaphor.

Ready For Recursion

A similar argument can be made for what is called recursive thinking or ‘thinking in brackets’. These terms can denote two (related) things: one is including one idea in the middle of another line of thought; the other is bracketing a number of entities together, such as when we make a generalisation or classification. The latter could also involve summing up a line of thought with an idea or even a symbol (such as a word) so that it can more easily be part of a more complex line of ideas. For a simple example: we take the ideas of mother and of sister and combine them, as in ‘mother’s sister’, into one idea, ‘aunt’. Then we may combine this with the idea of daughter, as in ‘aunt’s daughter’, to form the idea of ‘cousin’. Parcelling up our ideas in this way helps us to develop complex thoughts.

For another instance, we may develop an idea of what behaviour a choice will entail, and call it a ‘worthwhile’ endeavour. This might for example involve revising hard for the exams, with all the long nights of reading and making notes and the steadfast refusal to go out and enjoy yourself, and the ultimate reward of success in the exam and the value of the learning process itself, and the value of the knowledge thereby gained. Having in this way gained an understanding of the meaning of the word, we can then use the adjective ‘worthwhile’ without all the preceding description and narrative, to describe some other activity. The word ‘worthwhile’ starts to stand for more than the initial example: it stands for any complex narrative that involves hard work, test of character, endurance, sacrifice of present pleasure for future rewards, and ideas of what is of real value. So words are used like containers or bags to denote not just simple ideas but complex sets of ideas. This possibility of being able to load complex ideas into simple verbal units or thoughts, which in turn can be used in even more complex thinking, which can then itself be simplified to one idea or word, and so on, means that there is practically no end to the potential for nesting ideas one inside another.

An argument can also be made that we understand larger numbers by thinking of them as combinations of smaller units. Interestingly, we cannot think of larger numbers without language – try thinking of ‘147’ without any use of language/signs (mathematical signs are a form of language) – whereas the concepts of ‘one’, ‘two’ or ‘three’ are probably clear enough to visualise without the use of words. Mathematical notation also involves using a simple sign for often quite a complex operation.

The idea of classifying things (‘all dogs are mammals’), or having group or collective names (a ‘murder’ of crows), as well as the existence of abstract ideas such as ‘hope’ or ‘equality’, are arguably also developments from our ability to box up a set of ideas into one idea. It’s even possible that such core ideas about ourselves as the ‘soul’ or the ‘self’ originate in this ability to think of our experiences as contained in one unit. This in turn allows us to consider ourselves in certain ways: whether we are good or bad; whether we deserve what we get, and so on – such that we can judge ourselves and so become moral beings. So nesting, or recursion, is an aspect of language or thought that, arguably, differentiates humans from non-humans. And it can allow us to structure our thinking. Complex thinking is not just one thing after another, but one thing contained in another, like Russian dolls. We can say that, “The sunset is beautiful”, and, “John thinks that the sunset is beautiful”, and also that this whole sentence containing the two previous phrases – and that one (and that one! and so on ad infinitum) – are examples of nesting.

The other type of recursion I mentioned refers to the idea of temporarily going off at a tangent in the middle of a line of argument or narrative, such as when you say, “Mr Brown, who was wearing the same kind of coat as my brother, asked what time the bus was leaving.” The phrase inside the commas is a detour before coming back to the main point. This kind of sentence structure is a common example of recursion. Perhaps its genesis is from primitive hunters on the track of prey making a detour to find, say, water, before continuing their quest. It could be then that recursive thinking is itself a metaphor of detour behaviour. This would be an example not of thinking of one thing in terms of another, but of thinking as itself an activity emulating behaving in a certain way.

Conclusive Connections

Interestingly, the phenomena of recursion and metaphors may be connected. In his 2010 book The Tell-Tale Brain, V.S. Ramachandran argues that composite tool use, such as a sharp stone attached to a long stick (a spear) could have been a model for structure in sentence formation. He has found potential neurological evidence for this idea, showing that very close neural routes in the brain are used for structuring sentences, for thinking logically, and for fitting together physical things such as tools.

There seems to be a neurological basis for both recursion and for metaphor, and it involves brain areas not developed in other primates and so is a distinctly human trait. There remains however a question of whether language is necessary for this sort of thinking. It is clear though that even if it doesn’t initially generate these capacities, language greatly facilitates our ability to think in recursive and metaphorical ways.

So does our complex recursive and metaphorical use of language in fact differentiate us from all other animals – especially considering the advanced cognitive skills of such animals as chimpanzees and dolphins? They certainly have the ability to learn and recognise quite a few signs (words) for things, needs, or activities, to structure them in various meaningful ways (use grammar), and use them to convey some kind of meaning. However, the limitations on the use of (human) vocabulary and grammar in these animals means that their (human) ‘language’ is very poor compared to ours. More significantly, their apparent inability to use recursive or metaphorical language probably means that they cannot use language for anything like complex symbolic or abstract thinking. This indicates that human beings are different from other animals in the unique ways we can use metaphor and recursion to develop thought and ideas beyond a level other animals can think at.

Brian King is a retired Philosophy and History teacher. He has published an ebook, Arguing About Philosophy, and now runs adult Philosophy and History groups via the University of the Third Age.