Our ancient (some might say naive) conception of human nature has held to three doctrines. The first is that we are the creators of our choices and actions. We are not puppets, but responsible and free agents, able to chart our own path in the world. The second is that humans are special and different from other animals. Third, we assume that our perceptions, at least most of the time, accurately represent the world as it is.
The scientific study of consciousness has cast doubt on these three beliefs. Take away our free will. No one should be surprised to discover that mothers' brains change during pregnancy. Attributing our moods and behaviors to hormones has become the new common sense. But the idea that our thoughts and actions are a direct result of brain activity can also be troubling. If “my mind made me do it,” in what sense do I have control over myself?
Much of Crick's research seems to suggest that the brain is a kind of machine and that we merely carry out its commands. One lab creates models of the brain's circuits, cell by cell, as if they were a giant arrangement of microscopic Lego pieces. Another team has built a complete map of the fruit fly brain, proof that one day we can do the same with our own complex circuits. Crick's research on Alzheimer's disease is a sobering reminder that our cognitive abilities depend entirely on healthy, functioning brains, and that when those brains break down, so do we.
The fact that much of the above research was based on studies of birds, mice, and flies also suggests—beyond the need to insulate humans from experimental health risks—that we do not accept the idea that humans are fundamentally different from other animals. Seriously anymore. We study animal brains because they tell us things about human brains. But if the gap between humans and other animals is closing, does this mean that we should place less value on human life, or respect the lives of other creatures much more? In both cases, the hierarchy of species upon which we built our moral world was disturbed.
Perhaps most troubling is the idea that we do not see the world as it is. We have known for centuries that the precise way the world appears to us is determined by our senses, not the objects themselves. For example, the green color of grass is created by our visual system. But recent research goes further. Our brains don't just color our perceptions (sometimes literally), they actually construct them. Brains are not passive receptors of perception, but rather “prediction machines” that see what you expect to see, and hear what you expect to hear.
