What research has been done into the subjective preferences of different kinds of animals, and how that impacts their welfare needs?
For an example that most people would be familiar with, dogs tend to want to be much more active than cats. If you don't take your dog for a walk regularly or give it a lot of space to run around, that's a negative experience. Conversely, cats tend to be quite content to lie around and chill.
For a more controversial example, keeping pigs in enclosed spaces. Many years ago I worked at an intensive piggery operation. Despite a lot of public concern by animal welfare advocates about sow stalls and keeping pigs in small cages, it seemed to me that the pigs themselves didn't mind at all. They would quite contentedly walk into a cage without any objection, they wouldn't bolt for freedom when we let them out, they didn't try to get out of their cages, etc. And it's not as if they are just generically placid creatures that don't complain about anything. For example, social isolation seems to distress them greatly - on the rare occasions where we would need to separate one pig from the others for a few minutes (we did our best to avoid this, specifically because of the distress it caused them) they would panic and scream and try to get free so they could get back to the others.
Basically, I wonder to what extent do we mistake what animal welfare issues exist because we focus on the things that we humans would not like, rather than the things that the animals themselves don't like? To use another pig example, they really really love food. Every living thing loves food, but pigs really love food. I know the greedy pig is a stereotype, but it's a stereotype for a reason. But this would sometimes lead to situations where a sow would become overweight and to look after her long term health we would put her on a diet. They hate diets. Those sows on restricted feed schedules were angry and miserable as heck. And I think we just overlook how subjectively bad something like that is for them because we think "oh yeah, diets suck, I know what that's like, but it's worth it for your health". But we don't know what it's like for them, we only know what it's like for us.
I don't even really know how you would possibly go about trying to measure and quantify these things. How much does it bother fish to be in a small pond with thousands of other fish? How could you tell? But I'd be interested to hear about the work that's gone into this area, and I think I'd be almost as interested to hear about the research methods as I would the results.