A lot of people misunderstand Negative Reinforcement by confusing it with Punishment. Remember that Reinforcement is any consequence that encourages a behavior to continue and a Punishment is any consequence that discourages a behavior from continuing.
Negative Reinforcement starts with a negative condition (like pain) that encourages an organism to perform a behavior that will trigger a reward of relief. The pre-existing negative state can be natural or induced by a trainer.
Example of Natural Negative Reinforcement: If a person has a headache, then takes Tylenol and finds relief, the relief from the headache is reinforcement to take more Tylenol in the future if the headache returns. This is negative reinforcement because the person started out in a negative state.
Negative Reinforcement starts with a negative state and ends with a neutral state.
Positive Reinforcement starts with a neutral state and ends with a positive state.
In a way, you could say that Negative reinforcement involves the use of a pre-punishment.
Many scientists in the field of psychology argue that it is not needed to define the differences between negative and positive reinforcement because they are both so similar. For example, if an animal is hungry so you give it some food, you could say that this was negative reinforcement because he was originally in a negative state of hunger and now he has food which puts him in a neutral state. You could also say that this was positive reinforcement because he got a treat that he loves which probably caused him pleasure.
Example of Positive Reinforcement: You tell your nephew that if he says you’re his favorite uncle you will take him to the Zoo. He then says you are his favorite uncle and you take him to the zoo. He has been positively reinforced.
Example of induced Negative Reinforcement: You put your nephew in a headlock and tell him you will only release if he tells you that you are his favorite uncle. He tells you that you are his favorite uncle and you release.
Which of these two examples do you think will work to better gain your nephew’s trust?
Negative Reinforcement in Parrot Training
In order to use negative reinforcement in parrot training, you would usually have to set up some sort of pre-punishment to induce a negative starting state from which you can then provide relief. If a bird gets thrown into a negative state at the start of each training session then he is essentially being punished for coming out to train. This will teach him to avoid training sessions. That would be bad 
For this reason, it is recommended that parrot trainers only use positive reinforcement when training parrots when ever possible.
One important exception for parrot trainers
If your parrot is scared of you or hates you, then your presence in a room with him will cause a negative state that can then be relieved by you leaving the room. In this case it would be wise of you to use this to your benefit. Enter the room and approach the birds cage to where you see he starts to get uneasy. Wait for the parrot to calm down and then leave the room. The bird is learning that when he is calm, you do good things. This is a good example of when negative reinforcement is not only the best solution when parrot training, it may be the only solution.
