Do you give out/withhold affection to modify behavior?
I give out affection to modify behaviour, yes. Head scratches, talking (some of my guys find talking very affectionate), quick cuddles or belly rubs. I tend to give affection when reinforcing something that I like. I suppose you would say then that on the opposite end I remove affection to modify behaviour as well, but generally in this way I remove ATTENTION when doing so. I don't just remove affection, in which case still leaves you a lot of things you could do or say, but rather I remove attention from my dogs (ignoring them). But I suppose it would still encompass affection.
Use affection as a reward?
Yes, as described above.
Do you belive that showing affection while a dog is reactive or fearful reinforces reactive and fearful behaviors?
This is something that is very dog dependent. I don't give in to the old adage that 'coddling a fearful dog will make it more fearful". Not at all. I have found throughout my life that with true phobias and fears (rather than just discomforts), you cannot
reinforce fear, it's just not possible. I have found showing affection to truly fearful dogs in fearful situations usually either does nothing at all to change the behaviour, or it does help. And much to my surprise when I joined some forums I found out that there has been quite a lot written about this, and that there are so many others out there that agree with me!
You can't reinforce fear, because fear is a very primitive thing, found in some of the most basic animals that are thought to have a limited range of emotion. It is limbic, beyond the scope of operant abilities. Dog that are experiencing true fear (this does not include things like simple wariness, or shyness, or "fear periods", but rather deep-rooted fear in the form of phobias). Fear is so more complex than most people can imagine.
So to make it simple:
Would I coddle and pick up a puppy who entered the vet for the first time? Or who didn't want to walk by the trash can the first time it met one? Nope.
Would I re-assure and comfort my human fearful girl, by massage and using quiet, low-frequency sounds said in a slow tone of voice, and using touch to calm, if she got frightened by a person or we had company in the home? You betcha. And I've only noticed great things from it. I think to refuse your dog affection, during times of extreme stress and anxiety, is only doing a disservice to your dog. Often when your dog is truly afraid, it comes to you - most people who have dogs with phobias will realize this (the other option is fleeing in sheer panic and running anywhere but where the stimulus is). It's coming to you because you are its safe zone, because it feels you will provide safety and protection, that you will let no harm come to it. What message do you think you're sending when you either push the dog away or ignore any attempts at it trying to communicate its fear to you?
Like I said, fears and phobias are very complex situations. What people use this adage, they are lumping a whole lot of things under one umbrella. And it's not that black and white, it's just not.
Observations of wild canids and domestic canids as well, have shown that dogs DO seek comfort from one another, and do provide, in some manner, comfort to each other. Obviously this comfort is a different type of comfort than we humans provide, but it's the resulting emotion that matters, not how it was delivered. Humans and dogs have very different styles of comfort.
In a litter of puppies, their dam IS their comfort. When mama is around, they think that all is well. I think this is almost fundamental of normal puppies. Over the years I have seen so much of this to be true. When you take a litter outside for the first time (you'd have to do it across litters), compare taking the litter with the dam, and leaving the mother inside. If you take a litter outside without their dam, their first instincts are usually to lie in a huddle. This is called "packing". They are doing it a) because their dam isn't available and they aren't sure what to do, and b) packing is a behaviour that provides comfort (because they feel more safe) between siblings. However if you take a litter of pups outside with their dam, often the puppies will show little to no fear of the new area, and will go off and explore. I was fascinated as I observed litters over the last number of years to see this. The amount of comfort a dam provides to her young just by BEING there is astounding. Because it's what they understand. As they move out of the litter their comfort eventually comes from non-family - you or perhaps other dogs in your household. They can't help it, they are social creatures with social needs, and comfort, and acknowledgement of the animal's emotional state, is what they need.
Now, this is very dog-dependent and breed-dependent, but generally dogs like to sleep in huddles together. Such as the following (care of my lovely puppers):
http://img.photobucket.com/albums/v340/macmillk/Snuggle9.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle8.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle7.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle6.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle5.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle3.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle4.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle1.jpg
http://img.photobucket.com/albums/v340/macmillk/Snuggle.jpg
This is just another version of the packing behaviour, albeit modified to more mature animals. If dogs have an entire house to sleep in, with a dozen or more beds, why is it they choose to all try to sleep in the one same place together? Because it provides an aura of safety, it's comforting, knowing there is a "buddy" there that has your back. It's not just about warmth (most of these pictures are taken in hot summer days!). This is one of the ways dogs can provide comfort, there are many others.
Do you think it's mean to use affection as a means of shaping behaviors?
Not at all, unless of course you simply don't give affection at all. They are much too social to live a life of robotic non-affect.