4. The Measurement of Consciousness
© David Gamez, CC BY 4.0 https://doi.org/10.11647/OBP.0107.04
Consciousness just is not the sort of thing that can be measured directly. What, then, do we do without a consciousness meter? How can the search go forward? How does all this experimental research proceed?
I think the answer is this: we get there with principles of interpretation, by which we interpret physical systems to judge the presence of consciousness. We might call these preexperimental bridging principles. They are the criteria that we bring to bear in looking at systems to say (1) whether or not they are conscious now, and (2) which information they are conscious of, and which they are not.
David Chalmers,
On the Search for the Neural Correlates of Consciousness1
4.1 First-Person Reports about Consciousness (C-Reports)
I am standing with my friend Olaf in a field of poppies. ‘Look Olaf,’ I say, ‘the poppies are red, the sky is blue and the leaves are green.’ ‘By the blood of Grendel,’ he replies, ‘I can hear the sound of a bird singing and feel a sensation of warmth in my left foot.’
In earlier times my chat with Olaf would have been interpreted as a conversation about the world. Over the last three hundred years science has sucked colour, sound and warmth out of the world and reinterpreted them as consciousness. Statements like ‘The poppies are red’ or ‘There is a rusty helmet on the ground’ have become descriptions of consciousness.2
I am certain that I can speak about my consciousness. I cannot doubt that ‘The poppies are red’ is a true statement about my bubble of experience. I would be more willing to jettison the entire edifice of science, than abandon my belief that I can describe my consciousness.3
I can speak about my consciousness. I can describe my consciousness by pushing buttons and pulling levers. I can reply to questions about my consciousness by putting my brain into different states in a fMRI scanner.4
Olaf is alert. He can flexibly respond to novel situations. He can inwardly execute a sequence of problem-solving steps. He can execute a delayed reaction to a stimulus and respond to verbal commands.5 He is willing to bet a large amount of money that there is a rusty helmet in the field of poppies.6 These behaviours can be used to make reliable inferences about the contents and level of Olaf’s consciousness, even when he is not explicitly reporting his consciousness.7
I punch Olaf in the face. He falls to the ground and lies still. His stillness and lack of response are external signs that his brain is not associated with a bubble of experience, that his level of consciousness is zero.
When Olaf regains consciousness he exhibits groggy behaviour. l interpret this as a sign that he has a low level of consciousness. He is never quite the same again and often behaves in a similar way to a patient described by Damasio:
Suddenly the man stopped, in midsentence, and his face lost animation; his mouth froze, still open, and his eyes became vacuously fixed on some point on the wall behind me. For a few seconds he remained motionless. I spoke his name but there was no reply. Then he began to move a little, he smacked his lips, his eyes shifted to the table between us, he seemed to see a cup of coffee and a small metal vase of flowers; he must have because he picked up the cup and drank from it. I spoke to him again and again he did not reply. He touched the vase. I asked him what was going on and he did not reply, his face had no expression. […] Now he turned around and walked slowly to the door. I got up and called him again. He stopped, he looked at me, and some expression returned to his face—he looked perplexed. I called him again and he said, “What?”8
When Olaf is in this state he is not capable of executing a sequence of problem-solving steps. He does not flexibly respond to novel situations. He cannot execute a delayed reaction to a stimulus. We interpret his behaviour as a sign that he has zero consciousness, that he is not immersed in a bubble of experience.
Any behaviour that can be interpreted as a measurement of the level and/or contents of a person’s consciousness will be referred to as a c-report:
D2. A c-report is a physical behaviour that is interpreted as a report about a person’s consciousness.
A c-report is a measurement of consciousness. This measurement is indirect—Olaf’s bubble of experience does not appear in my bubble of experience.
Indirect measurements are standard scientific practice. When I measure the path of a particle, the particle does not directly appear in my bubble of experience. I have to create an experimental situation in which the particle creates a visible trace, such as a track of bubbles in a chamber. Theories about the physical world link the bubble track to the path of the invisible particle.
4.2 Reports about Non-Conscious
Mental Content (NC-Reports)
Olaf thinks a lot about his sweetheart Olga. As he crosses the field of poppies he is thinking about her corn-blond plaits, her inviting smile, her chequered billowing skirt, her strong smooth thighs. He is not aware of the stones in his boots, the white crosses in the field or the hot sun on his face. None of these are in his bubble of experience, although he could bring them into his bubble of experience if he stopped thinking about Olga’s thighs and focused on his body and surroundings.
As Olaf walks and thinks about Olga, the sensory data from the field of poppies is used by his brain to generate control signals that are sent to his muscles. This sensory data does not appear in his bubble of experience. It is unconscious or non-conscious information.
I present a picture of Olga to Olaf’s right eye and a picture of Olaf’s ex-wife Ingrid to his left eye. He experiences a phenomenon called binocular rivalry in which Olga’s picture is perceived for a few seconds while Ingrid’s is non-conscious, and then Ingrid’s picture becomes conscious and Olga’s non-conscious. When Ingrid’s picture is non-conscious it is still being processed by Olaf’s brain, which responds to the shape of her sharp tongue in her hard mouth.9
I show Ingrid’s picture to Olaf for 30 ms in the middle of a sequence of scrambled images. Under these conditions Ingrid’s picture does not enter Olaf’s bubble of experience, but it does cause Olaf to complete word fragments with Ingrid-related words and alters the conductivity of his skin.10 When I ask Olaf to guess which picture was shown he picks Ingrid’s picture more often than chance.11
All of these behaviours can be used to identify mental contents that are being processed non-consciously. They are nc-reports:
D3. A nc-report is a physical behaviour that is interpreted as a report about non-conscious mental content.
4.3 Platinum Standard Systems
C-reports about consciousness can be found everywhere. The sigh of waves can be interpreted as a c-report. Or consider the following snippet of code:
1. string input = "";
2. cout<<"Hello"<<endl;
3. while (input != "Goodbye"){
4. getline(cin, input);
5. if (input == "Are you conscious?")
6. cout<<"Yes"<<endl;
7. else if (input == "Are you a cute leetle kitten?")
8. cout<<"Yes, my eyes are blue and I cry 'Mew mew mew'."<<endl;
9. else if (input == "Goodbye")
10. cout<<"Goodbye"<<endl;
11. else
12. cout<<"Nice weather for the time of year."<<endl;
13. }
A computer running this code will claim that it is conscious. It will also claim that it is a cute leetle kitten. Neither claim is convincing.
My wife is a zombie. She hides from light and shuffles home from work with dead eyes, drinks in the pub with dead eyes, makes love with dead eyes. Her physical body is not associated with a bubble of experience. Her zombie statements about ‘consciousness’ are not descriptions of a bubble of experience. They are just empty sounds produced by biochemical processes.
My wife is a professional phenomenologist. She says many things that appear to be descriptions of a bubble of experience. I cannot directly observe her lack of consciousness, so how can I prove that she is a zombie? How can I prove that other people’s bodies are really associated with bubbles of experience? This is the traditional problem of other minds.
To scientifically study consciousness we need a physical system that is associated with consciousness. Since it is impossible to prove that particular physical systems are conscious, we have to set aside philosophical worries about solipsism and zombies and assume that one or more physical systems are actually conscious. I will do this by introducing the concept of a platinum standard system:
D4. A platinum standard system is a physical system that is assumed to be associated with consciousness some or all of the time.12
The term ‘platinum standard system’ is a reference to the platinum-iridium bar that was the first working definition of a metre.13 Other objects were directly or indirectly compared to this platinum-iridium bar to measure their length. The length of this bar could not be checked because it was defined to be one metre long: when this bar expanded, everything else contracted.14
Platinum standard systems are the starting point for consciousness science. Consciousness is simply assumed to be associated with these systems. When we have identified the relationship between consciousness and the physical world in platinum standard systems, we can use this knowledge to make inferences about the consciousness of other systems.
I was awarded a grant to study consciousness and ordered a platinum standard system from the supplier. It was delivered yesterday. I poured myself a coffee and strolled over to inspect it. A decent enough specimen with a bushy red beard, around 2 m tall. It made angry noises and rattled the bars of its cage. I prodded it with a stick and topped up its bowl of brown nuggets.
The supplier states that this system is associated with a bubble of experience. They are a reputable firm, so I have confidence in their claim. On the first day of our experiments we strapped the platinum standard system into a chair, held up a red apple and asked it for a c-report. It stated that it was conscious of a red apple. A promising start, but it had a crafty look in its eye—it might have been lying. Or its consciousness might be a delusional world that is completely disconnected from its behaviour. I was assured that this system shipped with a bubble of experience, but the supplier did not guarantee that I would be able to use c-reports to measure its bubble of experience.
Scientists studying consciousness need to measure consciousness. While a platinum standard system’s c-reports can be cross-checked for consistency, there is no ultimate way of establishing whether they are correct. Since c-reports are the only way in which consciousness can be measured, it has to be explicitly assumed that c-reports from a platinum standard system co-vary with its consciousness:
A1. During an experiment on consciousness, the consciousness associated with a platinum standard system is functionally connected to the platinum standard system’s c-reports.
A functional connection between consciousness and c-reports is a deviation from statistical independence—not necessarily a causal connection.15
A1 captures the idea that our consciousness is connected to our c-reports. When our consciousness changes, our c-reports change. This assumption does not specify the amount of functional connectivity between consciousness and c-reports, which will vary with the type of c-reporting. A1 is also explicitly limited to experiments on consciousness.16
Outside of experiments on consciousness it is possible that a system’s consciousness could be disconnected from its behaviour. Information gathered by consciousness experiments could be used to make inferences about the presence of consciousness in these situations. It could also be used to make deductions about the consciousness of systems that are not platinum standards, such as brain-damaged patients (see Section 9.2).
I contact the supplier. They issue me with a certificate that guarantees that their platinum standard systems’ c-reports are functionally connected to their consciousness (A1). We resume our experiments and identify a neural firing pattern that always occurs when the platinum standard system is conscious, and never occurs when it is not conscious. We have found the correlates of consciousness! We write up the results and submit our paper for publication.
The paper is rejected. We are devastated and enraged. One reviewer argues that our platinum standard system could have several consciousnesses. The second reviewer suggests that its bubble of experience could have features that are impossible to c-report under any circumstances. The third reviewer points out that it might be conscious when it is not c-reporting—it would just be unable to remember or report its consciousness. At best we have identified a correlate of part of its consciousness, not a true correlate of consciousness.
The systematic study of consciousness will be difficult or impossible if platinum standard systems are potentially associated with ghostly ecosystems of unreportable consciousnesses, or if many aspects of consciousness cannot be c-reported. Scientific studies have to assume that this is not the case:
A2. During an experiment on consciousness all conscious states associated with a platinum standard system are available for c-report and all aspects of these states can potentially be c-reported.17
This assumption states that every aspect of all of the conscious states that are associated with a platinum standard system can potentially be c-reported, even if they are not actually reported during an experiment.18 So we can use a variety of c-reports to extract a complete picture of a platinum standard system’s consciousness (see Section 4.8).19
A2 is incompatible with panpsychism.20 If all matter is conscious all the time, then c-reports cannot be used to measure all of a platinum standard system’s consciousness. If panpsychism was true, an apparently unconscious brain that was c-reporting zero consciousness would be associated with a bubble of experience.21
4.4 Pinning Consciousness to the Physical World
When I was a lad my father shone 700 nm light into my eyes and said ‘Red … red … red.’ My mother shone 450 nm light into my eyes and said ‘Blue … blue … blue.’ At a later point in time I c-report that there is a red patch in my bubble of experience. To make this report I use the association that I have learnt between an experience and a word. When I say that I am conscious of the red patch I am saying that I am having approximately the same colour experience that I had when I learnt the word ‘red’. The incoming electromagnetic waves have activated the same brain areas that were activated when I learnt the word ‘red’ as a child, which presumably are associatively linked to particular language or conceptual areas. My description of my conscious experience is a comparison with earlier experiences.22
We are sitting in a bare whitewashed room. A human ear is on the table in front of us. The colour of the torn edge of the ear is similar to the colour that I experienced when my father shone 700 nm light into my eyes. I make a c-report: ‘I am experiencing the colour red.’ The colour of the torn edge of the ear in your bubble of experience is similar to the colour that you experienced when your father shone 700 nm light into your eyes. You make a c-report: ‘I am experiencing the colour red.’
We both report that we are experiencing ‘red’, so we are apparently having the same conscious experience. But what if the colour produced by 700 nm electromagnetic waves in my bubble of experience is completely different from the colour produced by 700 nm electromagnetic waves in your bubble of experience? We have learnt the same mapping between incoming electromagnetic wave frequencies and colour names, so we will both make identical reports about the electromagnetic waves that we are exposed to, but nothing guarantees that these reports correspond to identical colour experiences. This is the classic problem of colour inversion, which is illustrated in Figure 4.1.23
Figure 4.1. Problem of colour inversion. a) A person teaches us the word ‘red’ by pointing to a coloured patch and making the sound ‘red’. Your colours are inverted relative to mine, so my red is your turquoise, and so on. We both learn to associate the colour that we experience with the sound ‘red’. b) We observe a severed ear on a table. The colour of the torn edge of the ear is similar to the colour that we experienced when we learnt the word ‘red’, so we both report that we are experiencing the colour red. The colours in our bubbles of experience are very different, but there is no way of detecting this in our external behaviour. Image © David Gamez, CC BY 4.0.
In the standard colour inversion scenario a single set of colours is linked in different ways to electromagnetic waves. Our bubbles of experience could also contain completely different sets of ‘colours’ that have no overlap between them. Or our consciousnesses could be different in more radical ways—different geometries, different experiences of space and time, differences that I am unable to imagine because I cannot imaginatively transform my bubble of experience into these other states.
In these scenarios two systems in similar physical states are associated with radically different bubbles of experience. Since they are making the same c-reports the differences between their bubbles of experience will not show up in scientific experiments. It will be impossible to systematically study the relationship between consciousness and the physical world under these conditions.
To address this issue scientists studying consciousness have to assume that identical states of the physical world are associated with identical conscious states. This can be expressed using the philosophical concept of supervenience.24 Since we are only concerned with a pragmatic approach to the science of consciousness, it is not necessary to assume that consciousness logically or metaphysically supervenes on the physical world. We just need to assume that the natural laws are such that consciousness cannot vary independently of the physical world:
A3. The consciousness associated with a platinum standard system nomologically supervenes on the platinum standard system. In our current universe, physically identical platinum standard systems are associated with indistinguishable conscious states.
4.5 Which Systems are Platinum Standards?
It is not known when consciousness emerges in the embryo or infant.25 We do not know whether birds or cephalopods are conscious.26 Brain-damaged people can inaccurately report their consciousness.27 No-one knows whether computers are capable of consciousness. We try and fail to use our imagination to decide whether consciousness is present in these systems.
I am an adult. I can smoke, drive and vote. Ten doctors claim that my brain is functioning normally. My brain does not contain unusual chemicals that might affect its operation. I am certain that this normally functioning adult human brain is associated with consciousness some of the time. If consciousness supervenes on the physical world (A3), then similar brains will be associated with similar consciousness:
A4. The normally functioning adult human brain is a platinum standard system.28
The normally functioning adult human brain is the only system that we confidently associate with consciousness. At a later point in time we might make further assumptions that extend the number of platinum standard systems. For example, we might assume that the red nodules on the genitals of an alien race are platinum standard systems.29
The science of consciousness is limited by the set of systems that we assume to be platinum standards. It is a science of the relationship between consciousness and platinum standard systems. Many relationships between consciousness and the physical world might not appear in normally functioning adult human brains. This would reduce the accuracy of our deductions about consciousness in non-human systems (see Section 9.2).
Some of the definitions and assumptions that have been introduced so far are illustrated in Figure 4.2.
Figure 4.2. Some of the definitions and assumptions that are required for scientific experiments on consciousness. The normally functioning adult human brain is a platinum standard system (A4), which is associated with consciousness (D4). Consciousness nomologically supervenes on the platinum standard system (A3) and all of it can be c-reported (A1, A2). Image © David Gamez, CC BY 4.0.
4.6 The Correlates of a Conscious State
Yesterday I lost consciousness in the street. My body lay crumpled on the concrete. Insects crawled over my face. Cappuccino-carrying commuters stepped over me on the way to the office. My body was just a thing—a part of the physical world that was not associated with a bubble of experience.
I am conscious now. The state of my brain now is different from the state of my brain when I lay unconscious on the street. If consciousness supervenes on the physical world (A3), something must be present in my brain now that is absent when consciousness is absent. This is a correlate of consciousness, which is defined as follows:
D5. A correlate of conscious state is a minimal set30 of one or more spatiotemporal structures in the physical world. This set is present when the conscious state is present and absent when the conscious state is absent. This will be referred to as a CC set.31
‘Spatiotemporal structures’ is a deliberately vague term that captures anything that might be correlated with consciousness, such as activity in brain areas, electromagnetic waves or quantum events. Chapters 6–8 discuss some of the spatiotemporal structures that might be members of CC sets.
Correlates defined according to D5 will be associated with consciousness wherever they are found.32 Suppose CC sets only contain electromagnetic wave patterns. When a particular electromagnetic wave pattern occurs in your brain, you are immersed in a particular bubble of experience. When the electromagnetic wave pattern is absent, you have a different bubble of experience or no consciousness at all. None of the other types of spatiotemporal structure in your brain have any effect on your bubble of experience.
I distract you with a soft toy: ‘Here reader, look at this, look… look… look at Teddy.’ While you are playing with its ears I extract your brain from your skull and keep it alive in a jar. I provide stimulation patterns that mimic the sensory-motor responses of your discarded body. I ensure that the electromagnetic wave pattern in your brain is identical to the one that was present when you were playing with Teddy. This is associated with a bubble of experience in which you are playing with Teddy, so you continue to have this experience.
I discard your brain’s biological tissue and replace it with silicon chips that are programmed to produce the same pattern of electromagnetic waves. You remain contentedly unaware of what is going on and continue to play with Teddy’s ears in your bubble of experience. Suppose that the same pattern of electromagnetic waves occurs by chance when I drop my phone. This will also be associated with a bubble of experience in which you are playing with Teddy’s ears.
Definition D5 enables me to state assumption A3 more precisely:
A3a. The bubble of experience that is associated with a CC set nomologically supervenes on the CC set. In our current universe, physically identical CC sets are associated with indistinguishable conscious states.
A correlation between A and B is the same as a functional connection between A and B—they are different ways of stating that A and B deviate from statistical independence.33 So a CC set can be described as a set of spatiotemporal structures that is functionally connected to a conscious state. This way of describing the relationship between consciousness and the physical world will play a role in what follows, so it will be formally stated as a lemma:
L1. There is a functional connection between a conscious state and its corresponding CC set.34
4.7 A Causal Relationship between Consciousness and the Physical World?
A science that invokes mental phenomena in its explanations is presumptively committed to their causal efficacy; for any phenomenon to have an explanatory role, its presence or absence in a given situation must make a difference—a causal difference.
Jaegwon Kim, Mind in a Physical World35
I was looking for love on the Internet. ButiDD’s profile looked promising: witty lines, sexy curves, hot pics. We arranged a date on Friday 5 August 2005 at 15:00 in a cafe on Hampstead Heath. When we met there was no chemistry. Conversation ground to a halt. I ate my cake. To cut through the boredom and silence I remarked ‘I am conscious of a sweet taste in my mouth.’ These sound vibrations led, through a complex chain of causes and effects, to Hurricane Katrina.
C-reports have physical effects. Speech vibrates the air, writing makes marks, gestures depress buttons and pull levers. These physical effects lead to further chains of causes and effects, which can be amplified into a hurricane or dissolve into background noise. Consciousness appears to be the source of c-reports, so it is natural to assume that it is the sort of ‘thing’ that can cause effects in the physical world.
A clearer definition of causation will help us to understand the relationship between consciousness and c-reports. First I will distinguish between conceptual and empirical theories of causation.36 Conceptual theories of causation elucidate how we understand and use causal concepts in our everyday speech. Empirical theories of causation explain how causation operates in the physical world—by reducing it to the exchange of physically conserved quantities, such as energy and momentum, or linking it to physical forces.37
Conceptual analyses of causation are popular in philosophy, but it is difficult to see how our use of ‘causation’ in everyday speech can help us to understand the causal interactions in the brain’s neural networks and the relationship between consciousness and the physical world.
Empirical theories of causation can precisely identify causal events and exclude cases of apparent causation between correlated events. They can easily relate the causal laws governing macro-scale objects, such as cars and people, to the micro-scale interactions between molecules, atoms and quarks. Empirical theories of causation are a much more appropriate starting point for studying the causal relationships between consciousness and c-reports.
A detailed discussion of the advantages and disadvantages of different theories of empirical causation is beyond the scope of this book, but it will be easier to analyze the c-reporting of consciousness with a concrete theory in mind. For this purpose I will use Dowe’s theory of empirical causation. This is the most fully developed conserved quantities approach and it has the following key features:38
- A conserved quantity is a quantity governed by a conservation law, such as mass-energy, momentum or charge.
- A causal process is a world line39 of an object that possesses a conserved quantity.
- A causal interaction is an intersection of world lines that involves the exchange of a conserved quantity.
This account of causation will be referred to as e-causation. The framework developed in this book relies on there being some workable theory of e-causation, but it does not depend on the details of any particular account. If Dowe’s theory is found to be problematic, an improved version can be substituted in its place.40
A car moves along a road at 5 m/s and knocks a fat man down (Figure 4.3a). In this e-causal interaction energy-momentum is transferred from the car to the man. This macro-scale e-causal interaction can be reduced down to the micro-scale e-causal interactions between the physical constituents of the car and man, in which atoms in the car’s bumper pass energy-momentum to atoms in the man’s legs (Figure 4.3b).
We can distinguish between true and false causes of this event. The car’s engine temperature is a macro-scale property of the physical world that moves along at the same speed as the car and also collides with the man (Figure 4.3c). However, the macro property of engine temperature does not exchange energy-momentum with the man, so it does not e-cause him to fall down, although it can e-cause other macro-scale effects, such as skin burns. Similar e-causal accounts can be given of the laws of other macro-scale sciences, such as geology, chemistry and biology.41
Figure 4.3. The relationship between macro- and micro-scale e-causal events. a) A car moving at 5 m/s collides with a fat man and knocks him down. This is a macro-scale e-causal event in which the car passes energy-momentum to the man. b) The macro-scale e-causal interaction between the car and man can be reduced down to the micro-scale exchanges of energy-momentum between atoms in the car and man. c) The temperature of the car’s engine is a macro-scale property that moves at 5 m/s and collides with the man. The engine temperature exchanges a small amount of energy-momentum with the man in the form of heat, but not enough to e-cause him to fall down. Image © David Gamez, CC BY 4.0.
It is generally assumed that the amount of energy-momentum in the physical universe is constant (as long as the reference frame of the observer remains unchanged). When part of the physical world gains energy-momentum, this energy-momentum must have come from elsewhere in the physical universe. It is also generally assumed that the net quantity of electric charge in the universe is conserved. If part of the physical world gains electric charge, another part of the physical world must have lost charge or there must have been an interaction in which equal quantities of positive and negative charge were created or destroyed. Similar arguments apply to other physically conserved quantities, which leads to the following assumption:
A5. The physical world is e-causally closed.
According to A5, any change in a physical system’s conserved quantities can in principle be traced back to a set of physical e-causes that led the system to gain or lose those conserved quantities at that time.
In everyday language we say that a person reports or describes their consciousness. This might naively be interpreted as the idea that consciousness directly or indirectly alters the activity of the brain’s speech areas, sending spikes to the larynx that lead to sound vibrations in the air.
The problem with this naive picture is that consciousness could only e-cause a chain of events leading to a c-report if it could pass a physically conserved quantity, such as energy-momentum or charge, to neurons in the c-reporting chain—for example, if it could push them over their threshold and cause them to fire.42 If the physical world is e-causally closed (A5), then a conserved quantity could only be passed from consciousness to a brain area if consciousness is a physical phenomenon, i.e. if consciousness is the correlates of consciousness.43
Consciousness is the correlates of consciousness if physicalism is correct. But it would be premature and controversial to base the scientific study of consciousness on this assumption. It is also absurd to claim that a bubble of experience is a pattern of invisible wave-particles. It would be much better to find a way of measuring consciousness that does not depend on the assumption that physicalism is true.
I have assumed that a conscious state is functionally connected to a CC set (L1) and that c-reports are functionally connected to consciousness (A2). To fully account for the measurement of consciousness we need an e-causal connection between CC sets and c-reports. This can be addressed by introducing a further assumption that fits in naturally with the current framework:
A6. CC sets e-cause a platinum standard system’s c-reports.
This states that the correlates of consciousness are the first stage in a chain of e-causation that leads to c-reports about consciousness.44,45 It can be difficult to measure e-causation, so in some circumstances A6 can be substituted for the weaker assumption:
A6a. CC sets are effectively connected to a platinum standard system’s c-reports.46
Assumption A6 is illustrated in Figure 4.4.
By themselves A6 and A6a do not say anything about the strength of the relationship between CC sets and c-reports. There could be a very weak e-causal chain leading from a CC set to a c-report, which could primarily be driven by unconscious brain areas. The weaker the connection between CC sets and c-reports, the more experiments will be required to identify CC sets.
Figure 4.4. Assumptions about the relationship between CC sets, consciousness and first-person reports. The labels S1, CC1, R1, etc. refer to any kind of spatiotemporal structure in the brain, such as the activation of a brain area, neural synchronization, electromagnetic waves, quantum events, and so on. They are only illustrative and not intended to correspond to particular anatomical paths or structures. An e-causal chain of sensory spatiotemporal structures, S1-S3, leads to the appearance of a spatiotemporal structure, CC1, that is functionally connected to consciousness. In this example the contents of consciousness are determined by sensory events, but in principle they could be independent of S1-S3—for example, if the subject was dreaming. CC1 is assumed to be the first stage in an e-causal chain of spatiotemporal structures, R1-R3, that lead to a verbal description of consciousness. Image © David Gamez, CC BY 4.0.47
4.8 The Limits of C-Reporting
You are looking at your reflection in a mirror. You see greying hair, burst capillaries, lengthening deepening lines. A tired sad sagging face. Your youth has gone. You will die soon. A sense of helpless fatality washes over you. You imagine how your face will look in the grave, under the wet earth, your empty eye sockets staring blankly at blackness, while the world rolls along and your existence fades away without trace.
Stick up your thumbs and interlace your fingers. Extend your arms to their full length in front of you. Look directly at your thumbnails. The area covered by your thumbnails is the high resolution part of your visual field. The rest is low resolution. When you look at your nose in the mirror only sketchy information is coming in from your gold earrings and beard. You cannot detect substantial changes that occur outside of the high resolution area.48
The limited extent of our high resolution vision is not a problem in daily life. When we require more information about a feature of our environment we make a rapid eye movement (known as a saccade) to bring this feature into high resolution vision. As you look in the mirror you are moving your eyes every ~200 ms. You inspect the pores on your nose, flick across to your left cheek, look up at your eyebrow, and so on.49
Depressed you pluck out a protruding hair. You squeeze a painful spot and wipe a stain from the mirror. A chewed-up cabbage leaf is trapped between your teeth. You remember your dental appointment tomorrow.
Your consciousness changes several times per second.50 As you look at your face in the mirror you are receiving fresh sensory information from your eyes and body and attending to different senses (moving from vision, to touch, to audition, etc.). You are shifting between past, present and possible futures: between memory, perception and imagination.
Describe your consciousness now. You were in a reverie—try again. The clock reads 22:59:50.874. Describe your consciousness when it changes to 23:00:00.000. Get ready … now.
When you started to describe your consciousness you were alert and speaking coherently. This external behaviour was a c-report of a high level of consciousness. Immobility and incoherent mumbling would have been a c-report of a low level of consciousness.
When the clock changed to 23:00:00.000 you started to describe your consciousness in natural language. But your consciousness changed when you uttered the first word—it became consciousness of that word. The consciousness that you had at 23:00:00.000 vanished when you started to describe it. Natural language is too slow to c-report consciousness in real time.
Ok, try a different strategy. The clock reads 23:01:46.340. Describe your consciousness when it changes to 23:02:00.000. Get ready … now.
This time you tried to remember your state of consciousness at 23:02:00.000. You converted an online bubble of experience into an offline bubble of experience. This memory preserves some washed-out unstable information about the visual consciousness that you had at 23:02:00.000. It holds little detail about the sounds, smells, tastes and body sensations that were in your bubble of experience at that moment. Your memory is also fragile—it is not like a computer file. As you describe your memory of your consciousness at 23:02:00.000 it becomes contaminated with details that came before or after the moment that you are trying to remember.
One more attempt. The clock reads 23:05:51.087. Describe your consciousness when it changes to 23:06:00.000. Get ready … now.
You could not accurately remember what your nose looked like at 23:06:00.000. So when I asked you to describe your consciousness you moved your eyes to look at your nose. You used the world as external memory.51 Your face is pretty stable, so perhaps you could use this method to generate a complete description of your consciousness at 23:06:00.000. However, this would not provide a description of your consciousness at 23:06:00.000: it would be a description of a series of moments of consciousness in which different aspects of your face enter the high resolution part of your bubble of experience. When you moved your eyes to obtain information about your nose, your consciousness at 23:06:00.000 was replaced with a new bubble of experience in which you were ‘zoomed in’ on your nose.
We cannot accurately describe a state of our consciousness. Natural language is too slow and vague. Our memory does not store enough details. Our consciousness at a given moment cannot be reconstructed by re-accessing information from our environment.52
Fixate your eyes on the small cross in the centre of the screen. Rest your index finger on the button in front of you. When I say ‘now’ I want you to press the button if there is a small red square in the bottom left hand corner of your visual field. Get ready … now.
Under controlled experimental conditions I can extract a small amount of accurate information about a specific aspect of your consciousness at a given time. The details of the measurement are set by the experimental conditions. The subject is only required to answer a simple yes/no question, without any need for memory or natural language.
This measurement method has the limitation that a subject can only answer one or two yes/no questions before their consciousness changes. This problem can be partly overcome by resetting their consciousness after each measurement. We can then use a large number of high precision probes to obtain a detailed measurement of one state of a subject’s consciousness.53
As an example, consider an experiment that measures a subject’s visual consciousness. To begin with the subject is asked to fixate on a cross on a screen. When they are looking at the cross it is replaced with a picture that remains on the screen for 200ms. This is long enough to ensure that the subject becomes conscious of the picture, and short enough to prevent them from moving their eyes while they are looking at it. The brief exposure attracts their attention—reducing the chance that their visual consciousness is remembering or imagining something else. The subject’s fixation on the cross ensures that their bubble of experience contains the same part of the picture each time. When the subject’s visual consciousness is put into this state one aspect of it can be measured with high precision. Repetition of this procedure can be used to progressively build up a detailed description of this state of consciousness.54
High precision measurement combined with the resetting of consciousness under experimental conditions is the most promising method for obtaining detailed descriptions of consciousness. But there are limits to the types of consciousness that can be reset, and a subject’s consciousness cannot be put into exactly the same state each time. These problems will reduce our ability to obtain detailed accurate measurements of consciousness.55
4.9 Formal Descriptions of Consciousness (C-Descriptions)
At present we are completely unequipped to think about the subjective character of experience without relying on the imagination—without taking up the point of view of the experiential subject. This should be regarded as a challenge to form new concepts and devise a new method—an objective phenomenology not dependent on empathy or the imagination. Though presumably it would not capture everything, its goal would be to describe, at least in part, the subjective character of experiences in a form comprehensible to beings incapable of having those experiences.
Thomas Nagel, What Is It Like to Be a Bat?56
Alice and Bob measure your consciousness at 14:02:00.050 and submit written reports of the results. Alice’s report contains several thousand words of natural language, similar to the work of Husserl, Heidegger and Merleau-Ponty. Bob’s report contains natural language descriptions of the experimental probes that he ran on your consciousness. It is written in the style of a methods section in a paper on experimental psychology. When you read either of these reports you are satisfied that they are a complete and accurate description of your consciousness at 14:02:00.050.
This verification process is inexact. It relies on an inaccurate memory of your state of consciousness. It is far from a complete validation. But it will have to do—it is all we can do.57
Formal descriptions play an important role in science. We have formal descriptions of many aspects of the physical world (mass, charge, voltage, magnetic field, etc.) that can be used to generate testable predictions. The Earth and Sun can be described as point masses of 5.97 × 1024 kg and 1.99 × 1030 kg. We can use this description of the Earth and Sun to predict the gravitational force between them (by substituting the masses for m1 and m2 in Newton’s equation F=Gm1m2/r2).58
Scientific theories of consciousness will eventually use mathematics to map between descriptions of consciousness and descriptions of the physical world (see Section 5.5). This will enable us to make strong testable predictions about the conscious state that is associated with a physical state. This will only become possible when consciousness can be described in a formal way that can be manipulated by algorithms and mathematical equations. This will be referred to as a c-description:
D6. A c-description is a formal description of a conscious state.
C-descriptions must be compatible with mathematics and they must be applicable to both human and non-human consciousness. We will have to develop methods for converting c-reports into c-descriptions and vice versa.
Natural language cannot be used for c-descriptions. It is vague, ambiguous, highly compressed and context dependent. Natural language descriptions of consciousness are difficult to analyze with algorithms and it is not obvious how they can be integrated with mathematical equations. Natural language also cannot be used to describe the consciousness of non-human systems, such as infants, bats or robots.59
C-descriptions could be written in a markup language, such as XML or LMNL. Markup languages are more precise and tightly structured than natural language, and they can be read by both humans and computers. They can capture complex nested hierarchies, which would enable them to describe the relationships between different parts and aspects of a conscious state.60
Mathematics could be used for c-descriptions. For example, Balduzzi and Tononi have suggested how conscious states can be described using high dimensional mathematical structures.61 Other mathematical techniques could be used to describe consciousness, such as category theory or graph theory.
An adequate c-description format is essential for the scientific study of consciousness. C-descriptions are at a very early stage of development and we are only just starting to explore solutions.
4.10 Summary
Scientists studying consciousness need to accurately measure conscious states. Consciousness is measured through first-person reports (c-reports), such as speaking or body gestures, which cannot be independently checked. This raises the philosophical problems of zombies, solipsism, colour inversion and the causal relationship between consciousness and the physical world. These problems cannot be solved. They can be neutralized by making assumptions that guarantee that consciousness can be accurately measured. The results of the science of consciousness can then be considered to be true given these assumptions.
I started by assuming that consciousness is functionally connected to first-person reports (A1). I then assumed that everything about a conscious state can be reported during an experiment and that there are no ghostly consciousnesses floating around that cannot be reported (A2). I handled colour inversion scenarios by assuming that consciousness supervenes on the brain (A3, A3a). First-person reporting does not break the causal closure of the physical world (A5) because reports about consciousness are e-caused by the correlates of consciousness (A6). All of these assumptions apply to systems that are assumed to be conscious (platinum standard systems) during experiments on consciousness. I assumed that normally functioning adult human brains are platinum standard systems (A4).
Consciousness cannot be described in real time using natural language, so we have to use experimental probes to measure specific aspects of a conscious state, and then reset the state and apply more probes until a complete measurement is obtained. The final output of a measurement of consciousness should be a c-description written in a tightly structured formal language, such as category theory or XML, that will support the development and testing of mathematical theories of consciousness.
This chapter also introduced the concept of a CC set. A CC set is a set of spatiotemporal structures in the physical world that is correlated with a conscious state (D5). The science of consciousness attempts to develop mathematical theories that describe the relationship between CC sets and conscious states. This is covered in the next five chapters.
