It's no secret that we need calories to fuel our body's basic energy needs. Yet many of us find it difficult to take in the right amount—and the right kind—of fuel. No matter how many guidelines we're given, we still crave what we know is bad for us.


Quite simply, cognition refers to thinking. There are the obvious applications of conscious reasoning—doing taxes, playing chess, deconstructing Macbeth—but thought takes many subtler forms, such as interpreting sensory input, guiding physical actions, and empathizing with others. The old metaphor for human cognition was the computer—a logical information-processing machine.

