PatK, I'm glad you posted this. It's been clear to me since childhood that many animals have at least some basic emotions like humans, and in dogs, it can be a very individual just as it is in people.
MRI studies on dogs
(below) by a neurologist are interesting. The first was a pilot study made in 2015, the latter an expansion.
How dogs love us | Dr. Gregory Berns
Below, his lecture is pretty long. I found the most interesting parts starting at 42:55 to the almost the end at 1:18:37. Those segments of his findings discuss Service/Assistance dogs, Olfactory/smell, Reward vs Praise, The Choice Test, Jealousy/aggression, and Impulse Control to the end of the video.
Gregory Berns: Decoding the Dog's Mind with Awake Neuroimaging