By Nick Chater

Now in fiction, while some characters are ‘two-dimensional’, others seem to have real ‘depth’. They can, indeed, assume in our imagination a vividness that may equal, or even exceed, that of some of our living acquaintances. We may attribute to them attitudes and beliefs beyond the printed page.

Yet such apparent depth is, of course, ‘in the eye of the beholder’: there are no facts about Anna Karenina’s life, save what Tolstoy gives us; no hidden motives lurking between the lines.

As for fictional characters, so for real people. The sense that behaviour is merely the surface of a vast sea, immeasurably deep and teeming with inner motives, beliefs and desires whose power we can barely sense is a conjuring trick played by our own minds. The truth is not that the depths are empty, or even shallow, but that the surface is all there is.

As we have already seen, it is awfully tempting – especially for psychologists – to suspect that while our everyday, common-sense explanations of ourselves and each other, as guided by beliefs, desires, hopes and fears, may be wrong in detail, they are right in spirit.

Anna’s leap to her death is, one may think, guided by some beliefs, desires, hopes and fears, even though she may not be able to tell us quite which beliefs, desires, hopes and fears. Her introspection is imperfect or perhaps untrustworthy.

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But the problem with our everyday view of our minds is far deeper: no-one, at any point in human history, has ever been guided by inner beliefs or desires, any more than any human being has been possessed by evil spirits or watched over by a guardian angel.

Beliefs, motives and other imagined inhabitants of our ‘inner world’ are entirely a figment of our imaginations. The stories we tell to justify and explain our own and others’ behaviour aren’t just wrong in detail – they are a thoroughgoing fabrication from start to finish.

Our flow of conscious thought, including our explanations of our own and each other’s behaviour, are creations in the moment, not reports of (or even speculations about) a chain of inner mental events.

Our mind is continually interpreting, justifying and making sense of our own behaviour, just as we make sense of the behaviour of the people around us, or characters in fiction.

If you cross-examine me, or any other reader, about Anna’s motivations (Q: ‘Did she think that jumping under the train would mean certain death?’ A: ‘Yes.’ Q: ‘Did she believe that Seryozha would be better off without her?’ A: ‘Possibly – though almost certainly quite wrongly’; and so on), I will generate answers, as quick as a flash.

So we clearly have the ability to fabricate justifications at will, but these justifications cannot, of course, be conjectures about Anna’s mental life, because Anna, being a fictional character, has no mental life.

If Anna were real, and had survived, we could cross-examine her, in her Swiss sanatorium, with just the same questions, and she too could reply, quick as a flash. And, for that matter, were you to cross-examine me about some prosaic aspect of my own life (for example, why I took the train, rather than driving, to London), I can come back with a string of explanations (about carbon emissions, traffic congestion, parking etc.).

The sheer inventiveness of our minds implies that the real Anna could be interpreting and justifying her own thoughts and behaviour, in retrospect, using exactly the imaginative powers that we are using when considering her as a fictional character by the imaginative work of Tolstoy himself in creating her story.

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And this suggests that this very same inventiveness could underlie the stream of justifications we provide to explain our everyday lives to ourselves and each other.

I want to convince you that the mind is flat: that the very idea of mental depth is an illusion. The mind is, instead, a consummate improviser, inventing actions, and beliefs and desires to explain those actions, with wonderful fluidity.

But these momentary inventions are flimsy, fragmented and self-contradictory; they are like a film set, seeming solid when viewed through the camera, but constructed from cardboard.

An improvising mind, unmoored from stable beliefs and desires, might seem to be a recipe for mental chaos. I shall argue that the opposite is true: the very task of our improvising mind is to make our thoughts and behaviour as coherent as possible – to stay ‘in character’ as well as we are able.

To do so, our brains must strive continually to think and act in the current moment in a way that aligns as well as possible our prior thoughts and actions. We are like judges deciding each new legal case by referring to, and reinterpreting, an ever-growing body of previous cases.

So the secret of our minds lies not in supposed hidden depths, but in our remarkable ability to creatively improvise our present, on the theme of our past.

The argument has two parts. First, I attempt to clear away what I take to be fundamental and widespread misunderstandings of how our mind works. I then turn to present a positive account of the brain as a ceaseless improviser.

More concretely, we will explore the psychological evidence that talk of beliefs, desires, hopes and fears is pure fiction. Yet it is such convincing fiction, and so effortlessly and fluently invented by our own brains, that we take it for reality.

We’ll find that almost everything we think we know about our minds is false. This is not the story from the psychology textbook. According to that story, common sense is roughly on the right track, but just needs to be modified, adjusted and filled out.

But these modifications and adjustments never seem to work. The common-sense mind and the mind we discover through experiment just don’t seem to fit together. The common-sense story needs to be abandoned, not patched up.

Is mental depth an illusion?

Yet while the textbooks don’t take a radical line, a growing number of philosophers, psychologists and neuroscientists do. I will point to the root cause of the problem with the common-sense view of the mind: that mental depth is an illusion.

We imagine that mirroring the outer world of people, objects, stars and noises there is an inner world of rich sensory experiences (the subjective experience of people, objects, stars and noises), not to mention our emotions, preferences, motives, hopes, fears, memories and beliefs.

The possibilities for exploration in this inner world seem vast. Just paying close attention to what we see and hear, and the states of our bodies, seems to reveal that our inner perceptual world is wonderfully rich; and that we just need to step off from direct sensory experience into the realm of the imagination that dreams, meditations and hypnosis seem to provide.

Or we can explore the vast archives of our memories, perhaps reliving fragments of childhood or student life; or we can discourse with ourselves endlessly about our beliefs and values.

There are many who suspect that the scale of our inner world is far greater still – that we should add into the mix subliminal perception, which slips into our minds without our noticing; that we have unconscious beliefs, motives, desires and perhaps even unconscious inner agents (for Freud, the id, ego, and superego; for Jung, the collective unconscious). And perhaps there is a self, or many selves, or a soul.

Many believe that with the right meditative practice, psychotherapy or even hallucinogenic drug, the doors to the rich inner world of the unconscious might be prised open. And, turning to neuroscience, it is natural to imagine that the contents of our inner world might one day be accessible to brain-scanners – which might ‘read off’ our beliefs, motives and feelings, whether conscious or not.

But all of this depth, richness and endless scope for exploration is utterly fake. There is no inner world. Our flow of momentary conscious experience is not the sparkling surface of a vast sea of thought – it is all there is.

And, as we shall see, each momentary experience turns out to be startlingly sketchy – at any moment, we can recognise just one face, or read just one word, or identify just one object.

And when, like our imagined Anna, rehabilitating in the Alps, we begin to describe our feelings, or explain our actions, we are only creating stories, one step at a time, not exploring a pre-existing inner world of thoughts and feelings.

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The more outré ‘inner worlds’ of dreams, or mystical or drug-induced states, are similarly nothing more than streams of invention – acts of the imagination, not voyages of inner discovery. And the interpretation of dreams, far from boring deep into our psyche, is no more than one creative act set atop another.

The aim of Part One is to help reinterpret our intuitions about the nature of our own minds, and to undercut misconceptions that have been repeated and even amplified in many areas of philosophy, psychology, psychoanalysis, artificial intelligence and neuroscience.

But if the intuitive picture – of a rich and deep ‘inner sea’ of which our conscious thought is merely the glittering surface – is so utterly wrong, the obvious question is: what possible alternative story about human thought and behaviour could there be?

In Part Two, we take up this question. If the mind is flat, then our mental lives must exist purely at the ‘mental surface’. Our brain is an improviser, and it bases its current improvisations on previous improvisations: it creates new momentary thoughts and experiences by drawing not on a hidden inner world of knowledge, beliefs and motives, but on memory traces of previous momentary thoughts and experiences.

The analogy with fiction is helpful here too. Tolstoy invents Anna’s words and actions as he writes the novel. But he strives to make Anna’s words and actions as coherent as possible – she should ‘stay in character’ or her character should ‘develop’ as the novel unfolds.

And when we interpret the behaviour of other people, and of ourselves, the same aim applies: a good interpretation is one that does not just make sense of the present moment, but links it with our past actions, words, and indeed interpretations.

Our brain is an engine that creates momentary conscious interpretations not by drawing on hidden inner depths, but by linking the present with the past, just as writing a novel involves linking its sentences together coherently, rather than creating an entire world.

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Conscious experience is therefore the sequence of outputs of a cycle of thought, locking onto, and imposing meaning on, aspects of the sensory world. That is, we consciously experience the meaningful interpretations of the world that our brain creates, seeing words, objects and faces, and hearing voices, tunes or sirens.

But we are never conscious either of the inputs to each mental step or each step’s internal workings. So we can report nothing to explain why we see an outcrop of rock as a pack of dogs, a fleeting facial expression as condescending or kindly, or why a line of poetry conjures up a vision of mortality or reminds us of childhood.

Each cycle of thought delivers a consciously experienced interpretation, but no explanation of where that interpretation comes from.

This is an exclusive extract from Nick Chater's new book The Mind is Flat - The Illusion of Mental Depth and The Improvised Mind published by Penguin.

Nick Chater, Professor of Behavioural Science, is a co-creator of our 3-day course Behavioural Science in Practice at The Shard. He lectures on the DBA and teaches Behavioural Sciences for the Manager on the Executive MBA and Executive MBA (London). He also teaches Principles of Cognition on the suite of MSc Business courses and Emotions in Business on the Undergraduate programme.

Follow Nick Chater on Twitter @NickJChater

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