[This is an excerpt from Part II of my latest book On Consciousness: Science & Subjectivity.]
Looking directly at the brain we see great orderly forests of neurons, each receiving input from thousands of others via bushy dendritic twigs and branches, and each sending forth its output by way of a single output limb called an axon.
Neurons send out electrical pulses 40–1,000 times per second, and they are all active at the same time.
A structure like the cortex is an immense, looming starship unto itself, containing by recent estimates 86 billion neurons. The interconnectedness of neurons is also remarkable; we can reach any single neuron in the brain from any other in less than seven steps. Cortical neurons project in vast elegant fiber bundles to the brain clumps nestling tightly underneath; 600 million of them project from one hemisphere to the other, and comparable numbers hang in great loops under each hemisphere to connect distant points between front and back. It is quite a beautiful and regular arrangement.
The brain is massively parallel — many things are happening at the same time — largely unconscious in its details, and widely decentralized in any task. The brain seems to show a distributed style of functioning, in which the detailed work is done by millions of specialized neural groupings without specific instructions from some command center. By analogy, the human body works cell by cell; unlike an automobile, it has no central engine that does all the work. Each cell is specialized for a particular function according to instructions encoded in its DNA, its developmental history, and chemical influences from other tissues. And the cell is of course the body’s basic unit of organization. In its own way the human brain shows the same distributed style of organization.
All this is widely understood today. What is rarely remarked, however, is that we can create access to any part of the brain using consciousness (see below, Figure 1). To gain control over alpha waves in the cortex we merely sound a tone or turn on a light when alpha is detected in the EEG, and shortly the subject will be able to increase the amount of alpha at will.
To control a single spinal motor neuron we merely pick up its electrical activity and play it back over headphones; in a half-hour subjects have been able to play drumrolls on their single motor neurons!
Of course we are not conscious of the details of control; conscious feedback seems to mobilize unconscious systems that handle the details. Biofeedback control over single neurons and whole populations of neurons anywhere in the brain is well established, and is considered to be “so ubiquitous that there seems to be no form of Central Nervous System activity… or part of the brain that is immune to it” (Buchwald, 1974).
What is odd about this, of course, is that consciousness of feedback from any neural activity is sufficient to establish control, though the great complexity of those activities is entirely unconscious. It is as if mere consciousness of results creates access to complex and unconscious systems that usually run things, free from interference.
We come to similar conclusions when we look at psychological evidence. Here are two examples.
1. The mental lexicon, meaning and grammar.
Perhaps half a second after you glance at a word on this page it is converted into a semantic code, to interpret its meaning, guided by the rules of grammar. Going from words to meanings requires a large, unconscious mental lexicon. The lexicon of educated speakers of English contains about 100,000 words. We can understand each one instantly, as soon as it is shown in a sentence that makes sense. Words are complicated things. The Oxford English Dictionary, for example, devotes 75,000 words to clarifying the many different meanings of the word set.
Set can be a verb, noun, or adjective. It can be a game in tennis or a collection of silverware. We can set a value on an antique, or build a stage set. Glamorous people make a jet-set, and unlucky ones a set of fools. The sun sets, but it is certainly not set in concrete. Mathematicians use set theory, and psychologists talk about set as readiness.
Consider your spontaneous experience of each of the following uses of set:
1. tennis: set
2. tools: set
3. put: set
4. value: set
5. stage: set
6. jet: set
7. fools: set
8. sun: set
9. theory: set
10. ready: set
Notice how quickly we change our minds about the meaning of set. In each example you probably had little difficulty understanding the intended meaning, given the first word of each pair to provide a frame (context). Simply becoming conscious of tools imparts an entirely different meaning to set.
This ability to combine two separate pieces of information has never been shown for unconscious input (e.g. Greenwald, 1992; MacKay, 1973). It seems that conscious‐ ness is required to integrate the meaning of each word pair. But everyday language always combines words: that is the role of grammar and semantics, both great unconscious bodies of knowledge. It therefore seems that understanding language — or anything else that integrates separate bits of information — demands the gateway of consciousness.
This is another case of the principle that consciousness creates widespread access to unconscious sources of knowledge, such as the mental lexicon, meaning and grammar. We will see this point again.
2. Autobiographical memory.
The size of long-term memory is unknown, but we do know that simply by paying attention to as many as 10,000 distinct pictures over several days, we can learn to recognize each of them without attempting to memorize them. Stephen Kosslyn writes:
“The capacity of our visual memories is truly staggering; it is so large that it has yet to be estimated…Perhaps the most staggering results are reported by Standing (1973) who showed some of his subjects 10,000 arbitrarily selected pictures for 5 seconds each… His findings showed that there is no apparent upper bound on human memory for pictures.”
Moreover, with immediate recall, Standing estimated that if one million vivid pictures were shown, 986,300 would be recognized if one were tested immediately afterward; even after a delay, he estimates that 731,400 would be recalled… Standing collected response times when subjects decided whether they recognized pictures; the results suggested the truly astounding conclusion that subjects could search 51,180 pictures per second in long-term memory! (Kosslyn, 1980, p. 129).
Remarkable results like this are common when we probe memory by merely asking people to choose between known and new pictures. Such “recognition tests” work well apparently because they represent the original conscious experience in its entirety. Here the brain does a marvelous job of memory search, with little conscious effort. You can get an everyday sense of this impressive performance from recognizing a film seen only once, many years ago, with a sudden sense of familiarity. Often we can even predict the rest of the film based on a single scene.
It seems that we create memories of the stream of experience merely by paying attention to something; but human beings are always paying attention, suggesting that autobiographical memory may be very large indeed.
Once again we have a vast unconscious domain, and we gain access to it using consciousness. Mere consciousness of some event helps to store a memory of it, and when we experience the same event again, it also helps us to recognize it, even out of millions of memories.
3. Consciousness is a gateway to vast domains of knowledge and control.
In sum, it seems that consciousness gives us vast access to billions of neurons in the brain and body, to the mental lexicon, and to an inestimably large source of autobiographical memories. Mere unaided consciousness may be sufficient to create rapid learning and accurate recognition.
Consciousness is also needed to trigger a great number of automatic routines that make up specific actions. All these effects of consciousness are unconscious. Consciousness may be considered as the gateway to these unconscious sources of knowledge.
Global Workspace Theory (GWT) began with this question: “How does a serial, integrated and very limited stream of consciousness emerge from a nervous system that is mostly unconscious, distributed, parallel and of enormous capacity?”
GWT is a widely used framework for the role of conscious and unconscious experiences in the functioning of the brain, as Baars first suggested in 1983.
A set of explicit assumptions that can be tested, as many of them have been. These updated works by Bernie Baars, the recipient of the 2019 Hermann von Helmholtz Life Contribution Award by International Neural Network Society form a coherent effort to organize a large and growing body of scientific evidence about conscious brains.
