As Hawkins notes, invariant representations can be viewed as a bug, as well as a feature, in human cognition; negative stereotyping and bigotry might have roots in such invariance. The strong element of prediction involved in perception also has a downside: It could underlie people's tendency to see what they want to see. Overall, though, Hawkins' model underscores the considerable capabilities of human intelligence. It provides a plausible explanation of how the speed and agility of human thought can exceed the capacities of computers, even though the latter have components that operate far faster than neurons.
The model may also offer insight into creativity, which arguably arises from the brain's propensity to make predictions. In Hawkins' view, there is a continuum between everyday actions and perceptions and the production of great novels or symphonies. The cortex during normal waking moments combines its invariant memories with the details of what is happening now; it is constantly predicting things that are similar to, but at least slightly different from, what it has experienced in the past. Our brains are geared to come up with something new.
Hawkins ventures that memory and prediction will be crucial to an understanding of consciousness, but he acknowledges that his model does not probe deeply into how and why consciousness exists. He draws a link between consciousness and memory through a thought experiment: If your memories of yesterday's activities were erased, so would be your sense that your behavior had been conscious. He speculates as to why vision, hearing, and other senses are (normally) experienced as qualitatively distinct, even though their inputs are all converted into patterns in the cortex. The answer, he suggests, might involve the diverse connections between the cortex and other parts of the brain.
In his final chapter, Hawkins writes enthusiastically about the prospects for intelligent machines. He expects rapid progress in the development of brain-like systems in the next several decades, citing speech recognition, vision, and smart cars as promising near-term applications. He imagines super-intelligent systems that will predict the weather, foresee political unrest, and understand higher-dimensional spaces. Yet he emphasizes that intelligent machines will not be similar to us. They will have something like a cortex and senses, but not human-like bodies, emotions, or experiences--things it would be very difficult, and generally pointless, to give them. They will not strive for power, wealth, status, or pleasure. They will not be angry at being "enslaved."
To illustrate the error of likening machines to human beings (and vice versa), Hawkins draws on a well-known thought experiment: A man who understands no Chinese is placed in a room with a wall slot through which he receives questions written in Chinese. Following a rule book, he replies to the questions with other Chinese symbols. To an outside observer, he seems to understand Chinese. But in fact, he has no idea what the questions or answers are about.
For Hawkins, the story of the Chinese Room points to limitations of conventional A.I. and of the Turing Test, the standard that a computer is intelligent if a human inquirer cannot distinguish its replies from a person's. Hawkins adds, however, that the Chinese Room would display intelligence if it contained a memory system that could make predictions about the content of the Chinese messages passed through the slot. This is an interesting wrinkle but a debatable point. One can imagine the man in the room adeptly foreseeing which symbols will follow which others but still not knowing what they mean.
The man who first asked us to imagine the Chinese Room was John Searle, a Berkeley philosopher who has written influentially about mind, language, and other subjects. His point was that a computer manipulates symbols but attaches no meaning to them; it understands nothing. Searle revisits the Chinese Room in Mind: A Brief Introduction. He rebuts the common counterargument that it is the overall system--man, room, rule book--that understands Chinese. The point is the same, he contends, even if the man is in an open field and has memorized the rule book. Indeed, Searle believes his original argument did not go far enough in debunking computer intelligence; something is a computer, he elaborates, only if an intelligent observer interprets it as such.
At the core of Mind: A Brief Introduction is Searle's effort to situate mental activity in the physical world. Consciousness, he argues, is a biological phenomenon; it is a process of the brain, much as digestion is a process of the stomach. He emphasizes, however, that consciousness cannot be dismissed as an illusion or defined in terms of lower-level neurobiological processes. Conscious states exist insofar as someone experiences them--they have a "first-person ontology"--and in this regard they are distinct from physical phenomena that have a "third-person ontology." The pain of banging into a coffee table (unlike the table itself) is real only because you feel it. Searle terms his position "biological naturalism" and contrasts it with the conventional categories of materialism and dualism.
Searle's picture leaves open the possibility of free will, defined here in contradistinction to determinism. In this view, quantum mechanical indeterminism at the micro-level may produce free will as a higher-level feature of the brain. In making decisions, the brain would draw upon the unpredictable behavior of its constituent particles. But wouldn't such freedom consist of mere randomness? Searle argues that this objection involves a fallacy of composition, confusing the properties of a system with those of its parts. Our pervasive experience of free will, he acknowledges, may be an illusion. But if so, it is a strange illusion, one that requires vast biological resources to maintain yet somehow survived evolution's travails.
Searle ranges broadly across the subject of mental phenomena, poking holes in much received philosophical and scientific wisdom. A key feature of conscious experience, he notes, is its unified structure; one normally encounters sights, sounds, and so on as part of one's overall environment. Neurobiology, he ventures, will ultimately benefit more from a "unified-field" approach to consciousness than from the currently favored "building-block" emphasis. Searle also takes issue with philosophical arguments that humans perceive not the real world but merely "sense data." Such claims, he contends, rely on slippery language and dubious assumptions.
The concept of the unconscious, Searle argues, is indispensable for explaining some forms of human behavior, but it is sometimes pushed beyond its applicability. Unconscious mental states, in his telling, are states that could in principle become conscious. It is possible, for instance, to believe that George W. Bush is president even when you are sound asleep. In Searle's view, however, cognitive scientists are incorrect to say, for example, that people see by performing "unconscious" computations on visual stimuli. The brain processes involved, much like the workings of the liver, are not the sort of thing that could be conscious; hence they are nonconscious rather than unconscious.
Searle closes with a discussion of the elusive concept of the self. A longstanding philosophical tradition, initiated by David Hume, regards the self as "a bundle of perceptions"; we have a series of experiences but not an inner essence. Searle argues, to the contrary, that consciousness, a capacity to initiate action, and an ability to act on the basis of reasons do amount to a self--a "non-Humean self" that is more than just a set of experiences. Having such a self provides continuity between one's past, present, and future; it is what enables a person to take responsibility and make plans.
Mind: A Brief Introduction and On Intelligence are thought-provoking and, no less important, anxiety-reducing. By dispelling overstated mechanistic claims arising from recent trends in neurobiology and philosophy, these books serve to combat public fears and forestall a possible backlash against science and technology. Humans can be part of the natural world without being mere machines, and without being outdone by our own machines.
These books cast light on how it is possible to have a rich mental life while living in a physical universe. In so doing, they throw up roadblocks against any push for political authoritarianism or social engineering that might arise from increased knowledge of how brains work. Far from advancing tyranny, neurobiology may be starting to provide a deeper understanding of what human freedom is all about.�
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