What happens to the language, emotions and decisions of a body governed by two hemispheres that no longer communicate with each other? The methodical answer to this question, which also allows us to understand how the hemispheres distribute functions, earned Roger Sperry the Nobel Prize–shared with Torsten Wiesel and David Hubel–in 1981. Sperry, along with his student Michael Gazzaniga, discovered an extraordinary fact that, just like Libet’s experiment, changed how we understand our construction of reality and, with it, the fuel of consciousness.
Without the corpus callosum, the information available to one hemisphere cannot be accessed by the other. Therefore, each hemisphere creates its own narrative. But these two versions are enacted by the same body. The right hemisphere only sees the left part of the world and also controls the left part of the body. And vice versa. Additionally, a few cognitive functions are fairly compartmentalized in each hemisphere. Typical cases are language (left hemisphere) and the ability to draw and represent an object in space (right hemisphere). So if patients with separated hemispheres are shown an object on the left side of their visual field, they can draw it but not name it. Conversely, an object to the right of their visual field is accessed by the left hemisphere and as such can be named but not really drawn.
Sperry’s great discovery was understanding how our consciousness creates a narrative. Imagine the following situation: patients with separated hemispheres are given an instruction in their left visual field; for example, that they will be paid money to lift up a bottle of water. Since it was presented to the left visual field, this instruction is only accessible to the right hemisphere. The patients pick up the bottle. Then they ask the patients’ other hemisphere why they picked it up. What do they respond? The correct answer, from the perspective of the left hemisphere–which did not see the instruction–should be ‘I don’t know.’ But that’s not what the patients say. Instead, they invent a story. They put forth reasons, such as that they were thirsty or because they wanted to pour water for someone else.
The left hemisphere reconstructs a plausible story to justify the participants’ action, since the real motive behind it is inaccessible to them. So the conscious mind acts not only as a front man but also as an interpreter, a narrator who creates a story to explain in hindsight our often inexplicable actions.
‘Performiments’: freedom of expression
Perhaps the most striking aspect of these fictional narratives created by patients with separated hemispheres is that they aren’t deliberate falsifications to hide their ignorance. The narrative is true, even to those fabricating it. Consciousness’s ability to act as an interpreter and invent reasons is much more common than we recognize.
A group of Swedes from Lund–near Ystad, where the detective Kurt Wallander also deals, in his own way, with the intricate tricks of the mind–produced a more spectacular version of the interpreter experiment. In addition to being scientists, these Swedes are magicians and, as such, know better than anyone how to force their audience’s choices, in making them believe illusions in a magic show as well as making them think they’ve made a decision completely freely in a science laboratory. Their way of putting free will in check is the show business equivalent of the project begun by Libet.
The experiment or trick, which here is the same thing, works this way: people are shown two cards, each showing a woman’s face, and they must choose which woman they consider more attractive and then justify their decision. That much is pretty straightforward. But sometimes the scientist–who also acts as the magician–gives the participants–who also act as the audience–the card they didn’t choose. Of course, the scientist does so using sleight of hand so that the switch is imperceptible. And then something extraordinary happens. Instead of saying, ‘Excuse me, I chose the other card’, most of the participants start to give arguments in favour of a choice they actually never made. Again they resort to fiction; again our interpreters create a story in retrospect to explain the unknown course of events.
In Buenos Aires, I set up, with my friend and colleague Andrés Rieznik, a combination of magic and research to develop our own performiments, performances that are also experiments. Andrés and I were investigating psychological forcing, a fundamental concept in magic that is almost the opposite of free will. It uses a set of precise tools to make spectators choose to see or do what the magician wants them to. In his book Freedom of Expression, the great Spanish magician Dani DaOrtiz explains exactly how the use of language, pacing and gaze allows magicians to make audience members do what they want them to. In the performiments, when the magician asks the crowd whether they saw something or not, or whether they chose the card ‘they really want’, the performer is actually following a precise, methodical script to investigate how we perceive, remember, and make decisions.
Using these tools we proved what magicians already knew in their bones: spectators don’t have the slightest idea that they are being forced and, in fact, believe they are making their choices with complete freedom. The spectators later create narratives–sometimes very odd ones–to explain and justify choices they never made, but truly believe that they have made.
We then moved this experiment from the stage to the lab. There we performed an electronic version of a forcing magic trick. We showed participants a very rapid sequence of cards. One of them was presented for slightly more time. This change remained unnoticed to our participants but made them choose in almost half of the trials the ‘forced’ card. The advantage of doing this experiment in the laboratory is that we could measure, while participants were observing the flashing deck and making their choices, their pupil dilation, an autonomic and unconscious response that reflects, among other things, a person’s degree of attention and concentration. And with this we discovered that there are indications in the spectators’ bodies that reveal whether the choice was freely made or not. Approximately one second after a choice, the pupil dilates almost four times more when people choose the forced card. In other words, the body knows whether it has been forced to choose or not. But the spectator has no conscious record of that. So our eyes are more reliable indicators of the true reasons behind a decision than our thoughts.
These experiments deal with the old philosophical dilemma of responsibility and, to a certain extent, question the simplistic notion of free will. But they do not topple this notion, not by a long chalk. We don’t know where or how Libet’s unconscious spark originates. At this point we can only make conjectures about the answers to these questions, as Lavoisier did with his theory of the caloric.
The prelude to consciousness
We saw that the brain is capable of observing and monitoring its own processes in order to control them, inhibit them, shape them, halt them or simply manage them, and this gives rise to a loop that is the prelude to consciousness. Now we will see how three seemingly innocuous and mundane questions can help us to reveal and understand the origin of and reason for this loop, and its consequences.
Why can’t we tickle ourselves?
We can touch ourselves, watch ourselves, caress ourselves, but we can’t tickle ourselves. Charles Darwin, the great naturalist and father of contemporary biology, took on this question in depth and with rigour. His idea was that tickling only works if one is taken by surprise, and that unexpected factor disappears when we do it to ourselves. It sounds logical, but it is false. Anyone who has ever tickled someone knows that it is just as effective–or even more so–if the victim is warned ahead of time. The problem of the reflexive impossibility of tickling oneself then becomes much more mysterious; it is not only that it isn’t a surprise.
In 1971, Larry Weiskrantz published an article in Nature entitled ‘Preliminary Observations on Tickling Oneself’. For the first time, tickles took centre stage in the research on consciousness. Then it was Chris Frith, another illustrious figure in the history of human neuroscience, who began to take tickling seriously–despite the oxymoron–as a privileged window into the study of the conscious mind.
/> Frith built a tickler, a mechanical device to allow people to tickle themselves. The detail that converted the game into science is the ability to change the intensity and delay in its action. When the tickler works with a scarce half-second delay, the tickling is felt as if someone else were doing it. When some time passes between our actions and their consequences, that produces a strangeness which makes them be perceived as being performed by others.*
Why doesn’t the image we’re looking at move when we move our eyes?
Our eyes are in constant movement. They make an average of three saccades or abrupt shifts per second. In each one, our eyes move at top speed from one side of an image to the other. If our eyes are moving all the time, why is the image they construct in our brains still?
We now know that the brain edits the visual narrative. It is like the camera director of the reality we construct. The stabilization of the image depends on two mechanisms that are now being tested out in digital cameras. The first is saccadic suppression; the brain literally stops recording when we are moving our eyes. In other words, for the split-second when our eyes are in motion we are blind.
This can be shown in a quick experiment at home: stop in front of a mirror and direct your gaze to one eye and then the other. When you do this your eyes will, of course, move. Yet, what you will see in the mirror are your immobile eyes. That is the consequence of the microblindness that occurs in the exact moment that our eyes are moving.
Even if we edit the mental movie as our eyes move, there is still a problem. After a saccade, the image should move the way it does in home movies or in Dogme films, when the frame instantly shifts from one point in the image to another. But that doesn’t happen. Why not? It turns out that the receptive fields in the neurons of the visual cortex–somewhat analogous to the receptors that codify each pixel of an image–also move to compensate for the eye movement. That generates a smooth perceptive flow, in which the image remains static despite the frame constantly shifting. This is one of many examples of how our sensory apparatus reconfigures drastically according to the knowledge that the brain has of the actions it is going to carry out. Which is to say, the visual system is like an active camera that knows itself and changes its way of recording depending on how it is planning to move. This is another footprint of the beginning of the loop. The brain informs on itself, it has a record of its own activities. This is the prelude to consciousness.
While in a very different framework, this is the same idea that governs the impossibility of tickling ourselves. The brain foresees the movement it will make, and that warning creates a sensory change. This anticipation cannot work consciously–one cannot deliberately avoid feeling tickles, nor voluntarily edit the visual flow–but therein lies the seed of consciousness.
How do we know that the voices in our head are ours?
We talk to ourselves all day long, almost always in a near whisper. In schizophrenia, this dialogue melds with reality in thoughts plagued with hallucinations. Chris Frith’s thesis is that these hallucinations result from the inability of schizophrenic patients to recognize that they are the creators of their inner voices. And since they don’t recognize them as their own, as with tickling, they cannot control them.
This argument withstands fierce experimental scrutiny. The region of the brain that codifies sounds–the auditory cortex–responds in a subdued way when we hear our own voice in real time. But if the same speech is played back and heard in a different context, it generates a cerebral response of greater magnitude. This difference is not observed in the auditory cortices of schizophrenics, whose brains do not distinguish when their voices are presented in real time or in a replay.
It turns out to be very difficult to understand the mind’s quirks when we don’t experience them ourselves. How can someone perceive their inner mental conversations as if they were external voices? They are inside us, we produce them, they are obviously ours. Yet there is a space in which almost all of us make the same mistake, again and again: in dreams. They are also fictions created by our imagination, but dreams exercise their own sovereignty; it is difficult, almost impossible, for us to appropriate their stories. What’s more, many times it is impossible to recognize them as dreams or products of our imaginations. That is why we feel relief when we wake up from a nightmare. In some sense, then, dreams and schizophrenia have similarities, since they both revolve around not recognizing the authorship of our own creations.*
In short: the circle of consciousness
These three phenomena suggest a common starting point. When an action is carried out, the brain not only sends a signal to the motor cortex–so the eyes and hands move–but also alerts itself to readapt beforehand. In order to be able to stabilize the camera, in order to be able to recognize inner voices as its own. This mechanism is called efferent copy, and it is a way that the brain has of observing and monitoring itself.
We have already seen that the brain is a source of unconscious processes, some of which are expressed in motor actions. Shortly before being carried out, they become visible to the brain itself, which identifies them as its own. This sort of cerebral signature has consequences. It happens when we move our eyes, when we can’t tickle ourselves, when we mentally recognize our own voice; we can think generically of this mechanism as an internal communication protocol.
A useful analogy here might be how, when a company decides to launch a new product, it lets its different departments know so that they can coordinate the process: marketing, sales, quality control, public relations, etc. When the company’s internal communications (its efferent copy) fail, incoherencies result. For example, the purchasing group observes that there is less availability of some raw material and has to guess the reason because it is not aware of the new product launch. In the same way, due to the lack of internal information, the brain comes up with its idea of the most plausible scenario for explaining the state of things. We can see in this analogy a metaphor for schizophrenia. It serves to convey the image of how delusions arise from a deficit in an internal communication protocol.
This is of course just an exercise of thought. There is no doubt that the company is not conscious of itself. But it sets a prerequisite of consciousness when it begins to inform itself of its own knowledge and its own states in a way that can be broadcast to different sections. However, this discussion may become less rhetorical and more concrete in the near future, when we build machines that can express all the features of consciousness. Will we consider them conscious? What rights and obligations will they have?
The physiology of awareness
We live in unprecedented times, in which the factory of thoughts has lost its opacity and is observable in real time. How does brain activity change when we are conscious of a process?
The most direct way to tackle this question is to compare cerebral responses to two identical sensory stimuli that, due to internal fluctuations–in attention, concentration or waking state of the subjects–follow completely different subjective trajectories. In one case we consciously recognize the stimulus: we can talk about it and report on it. The other occurs without a conscious trace, affecting the sensory organs and continuing its cerebral trajectory in a way that doesn’t result in a qualitative change in our subjective experience. This would be an unconscious or subliminal stimulus. Let’s think about the most tangible and common case of an unconscious stimulus: imagine that someone is speaking to us while we are placidly falling asleep. The words progressively vanish; we still hear sound arriving to our ears.
Let us begin by seeing how a subliminal image is represented in the brain. Sensory information arrives, for example, in the form of light to the retina, and turns into electrical and chemical activity that spreads through the axons to the thalamus, in the very centre of the brain. From there, the electrical activity spreads to the primary visual cortex, located in the back of the brain, near the nape. So, about 170 milliseconds after a stimulus reaches the retina, a wave of activity occurs in the brain’
s visual cortex. This delay is not only due to the conduction times in the brain but also to the construction of a cerebral state that codifies the stimulus. Our brain lives, literally, in the past.
The activation of the visual cortex codifies the properties of the stimulus–colour, luminosity, movement–so well that in the laboratory an image can be reconstructed based on the pattern of cerebral activation produced. What is most surprising is that this happens even if the image is presented subliminally. In other words, an image remains recorded for a while (at least) in the brain, even though that cerebral activity doesn’t produce a conscious mental image. With the proper technology, this recorded image can be reconstructed and projected. So today we are literally able to see the unconscious.
This whole river of cerebral activity that happens in the underground of consciousness is similar to that provoked by a privileged stimulus which is able to access the narrative of consciousness. This is interesting in and of itself and represents the cerebral trail of unconscious conditioning that was sketched out by Freud. But the unconscious is, in phenomenological and subjective terms, very different from the conscious mind. What happens in the brain to differentiate one process from the other?
The solution is very similar to what makes a fire spread or a tweet go viral. Some messages circulate in a local atmosphere, and certain fires remain confined to small sectors of a forest. But every once in a while, due to circumstances intrinsic to the object (the content of the tweet or the intensity of the fire) or the network (the dampness of the ground or the time of day in a social network), the fire and a tweet take over the entire network. They spread massively in an expansive phenomenon that begins to fuel itself. They become viral, and uncontrollable.
The Secret Life of the Mind Page 12