If you read Plaxco's book, he explains this and also is a link to a more in depth explanation.
Plaxco (not exact qoute)
1-conscious of every detail
2- conscious of some details, conditioned response on others (basically EVERYONE should be in this stage while training(provided you've been past stage one)-that's why we're there-right?)
3-"auto pilot" you have honed your skills and are now using you brain power to process the here and now-decision making. Although possible for you to "remind" yourself of what you need to do when making a shot, so potentially reverting to stage 2 in a gunfight.
Remember, our brain is like a computer-in training, you "program it" to perform a function and when that time comes to execute that program, you want it to do it without fail. That's why consistency is key so you don't have multiple programs that could cause hesitation, etc. It also has "x" amount of processing power, so the more you have to think about minute details, the slower your brain will function under stress.
www.unm.edu/~napperow/Chap5Coker.ppt
Cognitive Stage
High degree of cognitive activity
Attentional demands high, limited to movement production
Movements lack synchronization and appear choppy and deliberate
Numerous errors, typically gross in nature
Lacks capability to determine cause of errors or correct them
Associative Stage
More consistent
Attentional demands for movement production decrease
Fewer, less gross errors
Better at detecting cause of errors
Begin to develop appropriate error correction strategies
Autonomous Stage
Highest level of proficiency
Not all learners will reach this stage
Attention reallocated to strategic decision-making
Consistent
Confident
Make few errors and can generally detect and correct those errors that do occur