John Searle has a comprehensive review in the New York Review of Books (click on the link above). He disagrees with Humphrey but lays out the author’s argument in sufficient detail to make one want to read the book.
I intend to.
He agrees that the evolutionary account is not by itself sufficient to explain consciousness. But he thinks that with certain crucial additions we can account for qualitative subjectivity: “If this X factor [his expression for qualitative subjectivity] has to do with anything, it has to do with time.” He calls this aspect of consciousness the “extended present.” And he says we have no verbal way of describing the extended present. But he thinks we can understand it if we see how it resembles a work of art. He claims that we will get a deeper understanding of consciousness if we see the “analogy between a work of art and ‘a work of sensation.'” He thinks that studying Impressionism, Abstract Expressionism, and other kinds of art will enable us to explain what is so special about our conscious experience. For example, Humphrey writes, the painter Bridget Riley, a leading op artist,
explicitly acknowledges the “dual province of the senses,” making central to her vision the distinction between sensation and perception…. Riley is not interested in representing the outside world as she perceives it, as an impersonal fact. She wants only to show how it affects her—her eyes, her body.
Analogously, Humphrey continues, Monet, in his approach to painting a century earlier, “set out almost obsessively to capture the peculiar quality of present-tense experience,” or what he called “instantaneity.” For Humphrey, this is an example of how, in depicting a visual experience at a particular moment in time, some artists give precedence to describing how it feels to have that experience, rather than to describing the external realities that produced that experience. The conclusions that Humphrey draws from these observations, however, are difficult to follow:
Suppose, as an exercise in metaphor, we put a painting by Riley or Monet on the right-hand side of the mind-brain identity equation in place of the brain, will the painter’s tricks for depicting instantaneity genuinely help?
I think they not only help, they go right to the heart of it.
He thinks we have almost explained qualitative subjectivity, but we need one last thing, and that is feedback. To get consciousness we need a feedback mechanism whereby the “command signal” responds to the incoming stimulus by actually modifying the incoming sensory pathways in the brain. But he thinks the story that he told us already, about the primitive reaction of organisms to stimulus, is sufficient to explain the feedback mechanism. He writes, “Indeed, feedback has been a feature of sensation all along. Ever since the days when sensory responses were actual wriggles at the body surface, these responses have been having feedback effects by modifying the very stimulation to which they are a response.” So sustained feedback, together with a “very fine tuning,” by which he means “a precise matching of output with input, so as to provide exactly the right degree of reinforcement of the signal in the loop,” will produce consciousness. And the payoff, he tells us enthusiastically, the evolutionary advantage of all of this, is that it gives us a sense of “the Self.” It turns out that this is really the primary function of consciousness, not to give us information about the world, which comes from unconscious perception, but to give us a sense of the Self. And this also triumphantly answers the question why consciousness matters. “Consciousness matters,” he tells us, “because it is its function to matter. It has been designed to create in human beings a Self whose life is worth pursuing.”
Discoverers and Discoveries 