I want logic to back up what I think, not someone's opinion. Give me something substantive that can be measured. Thus far I have no reason to conclude you have a window that is any better than mine as to how chickens think.
Logic isn't "something that can be measured". Logic is something that is apparent without measurements. If I state "all apples are red, I have an apple, what color is it?", the logical answer is "red". It doesn't require you to actually see the very apple I have.
Here's the logic: Striving for the feeling of happiness is something that motivates an animal to do what's good for it. As far as a chicken knows, it's good for it to be able to walk wherever it wants to walk. It gives it more exercise, more places to find food, more hiding places, more places to lay eggs and to to dust bathe, and less likelihood of contracting parasites. Hence, chickens ought to feel happier the greater their ability to roam. Chickens in the jungle that were the happiest walking around in a small area likely reproduced less than chickens who roamed over a larger area. Hence, getting to walk where it wants to walk should logically increase its happiness compared to being constrained. It shouldn't be able to understand that it's safer from predators when it's penned up.
And even if they are happier walking around in a small area, what's the logic behind them being happier without even having the option of moving further?
Do you have any logical reason for a chicken to be happier without the ability to walk beyond the chicken run?