Disclaimer: The following is but a brief clarification on what the human brain does when one's behaviour is reinforced or punished. Thorough, exhaustive, and scholarly it is not.

Summary: Punishment, reinforcement, etc. of a behaviour creates an association in the mind of the affected party between the behaviour and the corresponding punishment, reinforcement, etc., the nature of which can only be known by the affected party. Take care when reinforcing or punishing others, as you may be effecting an unwanted association.

I've noticed the behaviourist concept of reinforcement thrown around a great deal on this site, and am worried a fair number of those who frequent it develop a misconception or are simply ignorant of how reinforcement affects humans' brains, and why it is practically effective.

In the interest of time, I'm not going to go into much detail on classical black-box behaviourism and behavioural neuroscience; Luke already covered the how one can take advantage of positive reinforcement. Negative reinforcement and punishment are also important, but won't be covered here.