I read this quote from Kashmir Csaky who has worked with Parrots in depth. It does explain better than I am able about how reinforcing any behavior works both negative and positive. "Parrot behavioral tip for the day. What is a reinforcer? Most people think that a reinforcer is a reward or anything that the bird likes. Often time it is, but not always. Very frequently stimuli like yelling and other histrionics actually increase unwanted behaviors. A reinforcer increases the strength and duration of the behavior that it immediately follows. It increases the rate of future behavior in the same or similar circumstance. So, if a behavior continues it is being reinforced.
Using treats is the easiest way to teach and reinforce behavior. However, it is not the only way and there are many reinforcers that are more effective than food. Experiment with other possible reinforcers, such as the tone of your voice, touch, movement, toys, the list goes on and on. I learned that work, attention, especially awe, is highly reinforcing when I took two of my birds to an elementary school. They were doing tricks for the children and their behavior was eager and fluent. Then one of the children asked me, Why are you giving them food? They're dropping it all to the floor. I looked down and saw a pile of treats that had accumulated on the floor. We do not decide what is reinforcing for our birds. They decide what is reinforcing for them and it is not the same thing in every circumstance."