Probability in Premack's principle

RabbitWho

Hello, I hope you're having a lovely day

http://en.wikipedia.org/wiki/Premack%27s_principle
http://en.wikipedia.org/wiki/David_Premack

Reinforcement is a relative property.Responses A, B, C have a descending rank order of probability. A will therefore reinforce both B and C. C will reinforce neither. This suggests that reinforcement is an absolute property. However, B corrects this view. B will reinforce C, but not A. B is both a reinforcer and not a reinforcer. Reinforcement is therefore a relative property.[2] < This makes absolutely no sense to me.
When drinking is more probable than running, drinking reinforces running. When the probabilities are reversed, running reinforces drinking.


Historically, consummatory responses, eating and drinking, have served exclusively as reinforcers, but consummatory responses are, like any other response, subject to reinforcement.
How are consummatory responses subject to reinforcement? Does this just mean that food is no good as a response if the organism is full?

*What does probability refer to here? Why are they using the word probability? Can someone give me a more real life example than the experiment with the kids and the candy machine? What are they actually saying here?


Reinforcement and punishment, traditionally contrasted as opposites, are in fact equivalent except for sign. If response A leads contingently to B, and B is more probable than A, A will increase in frequency (reinforcement); conversely, if A leads contingently to B, and B is less probable than A, A will decrease in frequency (punishment). The major contrast is not between reward and punishment; but between reward and punishment as contrasted with freedom. Freedom is the condition in which stimuli are freely (not contingently) available to an individual.

What do they mean by sign? Do they mean whether it's + probable vs. - probable?
What are they saying in that bit in Italics.



Thanks

Edit:
Okay I found this:
http://www.youtube.com/watch?v=jCgnOKpMvwA

According to another video that one is wrong because it uses food and the point is to be able to use other activities, not food, like getting a monkey to learn something he finds boring by allowing him to play with a fun puzzle afterwards.
*Well that makes me think that "more probable" is just something they say instead of saying "preferable" because they don't want to credit the organism with consciousness and they want a word that takes into account the fact that preferences depend on the situation. (You wouldn't want to eat ice cream if you were full) Is that right?
I'm still lost when it comes to the things in italics though.



-


[It says this is where psychology threads go but my thread on Instrumental Conditioning was moved to Biology so I apologize if there's some nuance I'm not aware of about where to put the threads... ]