By clearly showing his appreciation, Rick's boss is activating a reaction in Rick's mind. Much like little children when a person is given praise for something they've done correctly then they immediately want to do more things that are right and this causes a chain of reactions; the person will do good or well in the future because they like the praise they are being given and they want more of it. Because his boss is giving praise or appreciation for his work Rick will want to work more and even better because he'll want to get that same praise again at some point, thus Rick becomes a harder worker.
Hope this helped you a little!