operates beyond the horizon of conscious awareness we are blind to its workings. This system presents the fruit of its vast labors to us as though out of nowhere, and in a multitude of forms, from guid ing the syntax of a sentence to constructing complex full-blown mathematical proofs.
This back-of-the-mind attention typically comes to the center
of focus when the unexpected happens. You're talking on your cell phone while driving (the driving part is back-of-the-mind) and sud denly a horn honk makes you realize the light has changed to green.
Much of this system's neural wiring lies in the lower part of our brain, in subcortical circuitry, though its efforts break into awareness by notifying our neocortex, the brain's topmost layers, from below. Through their pondering, Poincare and Gauss reaped breakthroughs from the brain's lower layers.
"Bottom-up" has become the phrase of choice in cognitive sci ence for such workings of this lower-brain neural machinery.2 By the same token, "top-down" refers to mental activity, mainly within the neocortex, that can monitor and impose its goals on the subcor tical machinery. It's as though there were two minds at work.
The bottom-up mind is:
• faster in brain time, which operates in milliseconds
• involuntary and automatic: always on
• intuitive, operating through networks of association
• impulsive, driven by emotions
• executor of our habitual routines and guide for our ac
tions
• manager for our mental models of the world