Being You: A New Science of Consciousness

by Anil Seth

Deduction means reaching conclusions by logic alone: if Jim is older than Jane, and Jane is older than Joe, then Jim is older than Joe. If the premises are true and the rules of logic are followed, deductive inferences are guaranteed to be correct. Induction involves reaching conclusions through extrapolating from a series of observations: the sun has risen in the east for

all of recorded history, therefore it always rises in the east. Unlike deductive inferences, inductive inferences can be wrong: the first three balls I pulled out of the bag were green, therefore all balls in the bag are green. This may or may not be true.

In seeking the ‘best explanation’, abductive reasoning can be thought of as reasoning backward, from observed effects to their most likely causes, rather than forward, from causes to their effects – as is the case for deduction and induction.

Here’s an example. Looking out of your bedroom window one morning, you see the lawn is wet. Did it rain overnight? Perhaps, but

it could also be that you forgot to turn off your garden sprinkler. The aim is to find the best explanation, or hypothesis, for what you see: given the lawn is wet, what is the probability (i) that it rained overnight, or (ii) that you left the sprinkler on? In oth...

Bayesian inference tells us how to do this. It provides an optimal way of updating our beliefs about som...

Bayes’ rule is a mathematical recipe for going from what we already know (the prior) to what we should believe next (the posterior), based on what we are learning now (the likelihood). Priors, likelihoods, and posteriors are often called Bayesian ‘beliefs’ because they represent states of knowledge rather than states of the world. (Note that a Bayesian belief is not necessarily something I-as-...

of me is a coffee cup as to say that I believe that Neil Armstrong...

Perception is a rolling process, not a static snapshot.

While perceptual predictions flow predominantly in a top-down (inside-to-outside) direction, prediction errors flow in a bottom-up (outside-to-inside) direction. These prediction error signals are used by the brain to update its predictions, ready for the next round of sensory inputs.

What we perceive is given by the content of all the top-down predictions together, once sensory prediction errors have

been minimised – or ‘explained away’ – as f...

Action is inseparable from perception. Perception and action are so tightly coupled that they determine and define each other. Every action alters perception by changing the incoming sensory data, and every perception is the way it is in order to help guide action.

Let’s check in one final time with our imagined brain, sealed inside its bony prison. We now know that this brain is far from isolated. It swims in a torrent of sensory signals from the world and the body, continually directing actions – self-fulfilling proprioceptive predictions – which proactively sculpt this sensory flow. The incoming sensory barrage is met by a cascade of top-down predictions, with prediction error signals streaming upward to stimulate ever better predictions and elicit new actions. This rolling process gives rise to an approximation to Bayesian inference, a GoodEnough Bayesianism in which the brain settles and resettles on its evolving best guess

about the causes of its sensory environment, and a vivid perceptual world – a controlled hallucination – is brought into being.

Understanding controlled hallucinations this way, we now have good reasons to recognise that top-down predictions do not merely bias our perception. They are what we perceive. Our perceptual world alive with colours, shapes, and sounds is nothing more and nothing less than our brain’s best guess o...

Consider the sea squirt. In its juvenile stage this simple animal has a well-defined though rudimentary brain, which it uses as it searches for an appealing rock or lump of

coral on which to spend the rest of its life filter-feeding on whatever drifts by. Having found one and attached itself, it digests its own brain, retaining only a simple nervous system. Some people have used the sea squirt as an analogy for an academic career, before and after finding a permanent university position.

When we experience the world as being ‘really out there’, this is not a passive revealing of an objective reality, but a vivid and present projection – a reaching out to the world from the brain.

What we call ‘hallucination’ is what happens when perceptual priors are unusually strong, overwhelming the sensory data so that the brain’s grip on their causes in the world starts to slide.

In cognitive science, the phenomenology of objecthood has been most thoroughly explored by ‘sensorimotor contingency theory’. According to this theory, what we experience depends on a ‘practical mastery’ of how actions

change sensory inputs. When we perceive something, the content of what we perceive is not carried by the sensory signals; instead it emerges from the brain’s implicit knowledge about how actions and sensations are coupled. On this view, vision – and all our perceptual modalities – are things an organism does, not passive information feeds for a centralised ‘mind’.

rating busy scenes as lasting longer than quiet scenes,

time perception can emerge, at least in principle, from a ‘best guess’ about the rate of change of sensory signals,

We can respond more quickly and more effectively to something happening in the world if we perceive that thing as really existing.

To put it another way, even though perceptual properties depend on top-down generative models, we do not experience the models as models. Rather, we perceive with and through our generative models, and in doing so out of mere mechanism a structured world is brought forth.

A chair has a mind-independent existence; chairness does not.

Another good example is provided by motion aftereffects, such as the waterfall illusion. Stare straight at a waterfall (or at a video

of a waterfall) for a while then look away, perhaps at a rockface next to it. The rockface will appear to move upwards, while also appearing to remain in the same place.

It may seem as though the self – your self – is the ‘thing’ that does the perceiving. But this is not how things are. The self is another perception, another controlled hallucination, though of a very special kind.

From the sense of personal identity – like being a scientist, or a son – to experiences of having a body, and of simply ‘being’ a body, the many and varied elements of selfhood are Bayesian best guesses, designed by evolution to keep you alive.

I think the correct – but admittedly strange – answer is that both are the real Eva.

We intuitively treat experiences of self differently from experiences of the world.

When it comes to the experience of being you it seems harder to resist the intuition that it reveals a genuine property of the way things are – in this case an actual self – rather than a collection of perceptions. One intuitive consequence of assuming the existence of an actual self is that there can be only one such self, not two, or two thirds, or many. The idea that the self is somehow indivisible, immutable, transcendental, sui generis, is baked

into the Cartesian ideal of the immaterial soul and still carries a deep psychological resonance, esp...

But it has also been repeatedly held up to sceptical scrutiny by philosophers and religious practitioners, as well as more recently by psychedelic psych...

Kant, in his Critique of Pure Reason, argued that the concept of the self as a ‘simple substance’ is wrong, and Hume talked about the self as a ‘bundle’ of perceptions. Much more recently, the German philosopher Thomas Metzinger wrote a very brilliant book called Being No One – a powerful deconstruction of the singular self. Buddhists have long argued that there is no such thing as a permanent self and through meditation have attempted to reach entirely s...

sense of self with heady mixtures of ritual and dimethyltryptamine. In neurology, Oliver Sacks and others have chronicled the many ways in which the self falls apart following brain disease or damage, while split-brain patients – who we met in chapter 3 – raise the possibility that one self might become two. Most curious of all are craniopagus twins, who are not only physically conjoined but also share some of their brain structures. What could it mean to be an individual self, w...

embodied selfhood

perspectival self

volitional self.

For many people the notion of ‘free will’ captures that aspect of being-a-self which they’re least willing to give up to science.

Fig. 16: Ernst Mach, Self-portrait (1886).

All these ways of being-a-self can be in place

prior to any concept of perso...

the identity that can be associated with a name, a history, and a future. As we saw with the teletransportation paradox, for personal identity to exist, there has to be a personalised prior history, a thread of autobiogr...

narrative...

The social self is all about how I perceive others perceiving me.

It is the part of me that arises from my being embedded in a social network. The social self emerges gradually during childhood and continues to evolve throughout life, though it may develop differently in conditions like autism. Social selfhood brings with it its own gamut of emotional possibilities, from new ways to feel bad – like guilt and shame – to ways of feeling good, such as pride, love, and belonging.

For each of us – in normal circumstances – these diverse elements of selfhood are bound together, all of a piece, all subsumed within an overarching unifie...