Ray Kurzweil - How to Create a Mind - The Secret of Human Thought Revealed

Another definition of qualia is the feeling of an experience. However, this definition is no less circular than our attempts at defining consciousness above, as the phrases “feeling,” “having an experience,” and “consciousness” are all synonyms. Consciousness and the closely related question of qualia are a fundamental, perhaps the ultimate, philosophical question (although the issue of identity may be even more important, as I will discuss in the closing section of this chapter).

So with regard to consciousness, what exactly is the question again? It is this: Who or what is conscious? I refer to “mind” in the title of this book rather than “brain” because a mind is a brain that is conscious. We could also say that a mind has free will and identity. The assertion that these issues are philosophical is itself not self-evident. I maintain that these questions can never be fully resolved through science. In other words, there are no falsifiable experiments that we can contemplate that would resolve them, not without making philosophical assumptions. If we were building a consciousness detector, Searle would want it to ascertain that it was squirting biological neurotransmitters. American philosopher Daniel Dennett (born in 1942) would be more flexible on substrate, but might want to determine whether or not the system contained a model of itself and of its own performance. That view comes closer to my own, but at its core is still a philosophical assumption.

Proposals have been regularly presented that purport to be scientific theories linking consciousness to some measurable physical attribute—what Searle refers to as the “mechanism for causing consciousness.” American scientist, philosopher, and anesthesiologist Stuart Hameroff (born in 1947) has written that “cytoskeletal filaments are the roots of consciousness.” 2 He is referring to thin threads in every cell (including neurons but not limited to them) called microtubules, which give each cell structural integrity and play a role in cell division. His books and papers on this issue contain detailed descriptions and equations that explain the plausibility that the microtubules play a role in information processing within the cell. But the connection of microtubules to consciousness requires a leap of faith not fundamentally different from the leap of faith implicit in a religious doctrine that describes a supreme being bestowing consciousness (sometimes referred to as a “soul”) to certain (usually human) entities. Some weak evidence is proffered for Hameroff’s view, specifically the observation that the neurological processes that could support this purported cellular computing are stopped during anesthesia. But this is far from compelling substantiation, given that lots of processes are halted during anesthesia. We cannot even say for certain that subjects are not conscious when anesthetized. All we do know is that people do not remember their experiences afterward. Even that is not universal, as some people do remember—accurately—their experience while under anesthesia, including, for example, conversations by their surgeons. Called anesthesia awareness, this phenomenon is estimated to occur about 40,000 times a year in the United States. 3 But even setting that aside, consciousness and memory are completely different concepts. As I have discussed extensively, if I think back on my moment-to-moment experiences over the past day, I have had a vast number of sensory impressions yet I remember very few of them. Was I therefore not conscious of what I was seeing and hearing all day? It is actually a good question, and the answer is not so clear.

English physicist and mathematician Roger Penrose (born in 1931) took a different leap of faith in proposing the source of consciousness, though his also concerned the microtubules—specifically, their purported quantum computing abilities. His reasoning, although not explicitly stated, seemed to be that consciousness is mysterious, and a quantum event is also mysterious, so they must be linked in some way.

Penrose started his analysis with Turing’s theorems on unsolvable problems and Gödel’s related incompleteness theorem. Turing’s premise (which was discussed in greater detail in chapter 8) is that there are algorithmic problems that can be stated but that cannot be solved by a Turing machine. Given the computational universality of the Turing machine, we can conclude that these “unsolvable problems” cannot be solved by any machine. Gödel’s incompleteness theorem has a similar result with regard to the ability to prove conjectures involving numbers. Penrose’s argument is that the human brain is able to solve these unsolvable problems, so is therefore capable of doing things that a deterministic machine such as a computer is unable to do. His motivation, at least in part, is to elevate human beings above machines. But his central premise—that humans can solve Turing’s and Gödel’s insoluble problems—is unfortunately simply not true.

A famous unsolvable problem called the busy beaver problem is stated as follows: Find the maximum number of 1s that a Turing machine with a certain number of states can write on its tape. So to determine the busy beaver of the number n , we build all of the Turing machines that have n states (which will be a finite number if n is finite) and then determine the largest number of 1s that these machines write on their tapes, excluding those Turing machines that get into an infinite loop. This is unsolvable because as we seek to simulate all of these n -state Turing machines, our simulator will get into an infinite loop when it attempts to simulate one of the Turing machines that does get into an infinite loop. However, it turns out that computers have nonetheless been able to determine the busy beaver function for certain n s. So have humans, but computers have solved the problem for far more n s than unassisted humans. Computers are generally better than humans at solving Turing’s and Gödel’s unsolvable problems.

Penrose linked these claimed transcendent capabilities of the human brain to the quantum computing that he hypothesized took place in it. According to Penrose, these neural quantum effects were somehow inherently not achievable by computers, so therefore human thinking has an inherent edge. In fact, common electronics uses quantum effects (transistors rely on quantum tunneling of electrons across barriers); quantum computing in the brain has never been demonstrated; human mental performance can be satisfactorily explained by classical computing methods; and in any event nothing bars us from applying quantum computing in computers. None of these objections has ever been addressed by Penrose. It was when critics pointed out that the brain is a warm and messy place for quantum computing that Hameroff and Penrose joined forces. Penrose found a perfect vehicle within neurons that could conceivably support quantum computing—namely, the microtubules that Hameroff had speculated were part of the information processing within a neuron. So the Hameroff-Penrose thesis is that the microtubules in the neurons are doing quantum computing and that this is responsible for consciousness.

This thesis has also been criticized, for example, by Swedish American physicist and cosmologist Max Tegmark (born in 1967), who determined that quantum events in microtubules could survive for only 10 −13seconds, which is much too brief a period of time either to compute results of any significance or to affect neural processes. There are certain types of problems for which quantum computing would show superior capabilities to classical computing—for example, the cracking of encryption codes through the factoring of large numbers. However, unassisted human thinking has proven to be terrible at solving them, and cannot match even classical computers in this area, which suggests that the brain is not demonstrating any quantum computing capabilities. Moreover, even if such a phenomenon as quantum computing in the brain did exist, it would not necessarily be linked to consciousness.