They definitely do show sympathy, sadness, fear and joy, which are unrelated to being rewarded with food and trained behaviour.

I don’t see why they shouldn’t have a full range of emotions. It seems simpler and more natural than developing a transactional response only.

The bigger question is what emotions even are. If it’s a chemical or biological reaction then it’d be weird if other mammals didn’t have about the same emotions as humans.

It’s difficult to see how an animal feels unless you know it well. I can mostly see how my own dog is doing, but I have no idea what mood a random dog on the street is in.