It's a mistake to think animals are so different from us. They don't all have the same nuanced emotions, for instance cats seem to lack guilt, they're not nearly as wired to be social, but dogs, being pack animals have it in abundance.
Exactly. We and gorillas share much more behavior than most realize. Everything from desire for friendship and love to desire for social status and achievement work pretty much EXACTLY the same. A book which made me realize this is "Sex and War: How Biology Explains Warfare and Terrorism and Offers a Path to a Safer World". Title seems a bit unrelated to this topic, but this book basically shows that pretty much all our motivations are inherited from our great ape ancestors (and are shared by chimps – out closest living specie in terms of behavior).
These are just hints to similar behaviour, _no definite proof_ is available and impossible to obtain.
Which is why behavioural biologists don't even go down that path of "humanizing" animals - all they do is link certain behaviour to certain actions (famous example: anal-sniffing as sexual behaviour in guinea-pigs or dogs). Looking at animals through the "human glass" can lead to some insights, but can certainly lead to terribly wrong results, too:
It's like overfitting a statistical model, you'll get noise where you expect results.
Could some animals have some richer emotions which we don't have? For example, some animals with Tetrachromacy can have a reacher color space than us. http://en.wikipedia.org/wiki/Tetrachromacy
Many birds can see ultraviolet, it's fairly common since it seems to allow them to differentiate flowers the same way many insects do. Some flowers look completely different in the UV spectrum (http://www.dailymail.co.uk/sciencetech/article-473897/A-bees...). This is why it's important that many types of pet birds have some natural daylight.
As for emotions, that's a harder thing to prove. Dolphins are intelligent enough they should be classified as sentient non-human persons according to more progressive scientists. They have the richest range of emotions we've seen outside of chimpanzees, and to be honest, chimpanzees are so very nearly human it's quite amazing. They don't seem to lack any faculties that humans have, but some of their emotions are just less pronounced or developed.
Sometimes it seems the only reason that chimpanzees aren't affected more emotionally is that they don't understand the implications of what's happening. It's just ignorance more than a lack of emotion.
What might exist in the way of emotions humans don't have is things that are bio-chemical. Nature has a way of "rewarding" behaviors that are productive with a positive feeling. Do cuttlefish feel something other than love when doing their dances? What does an octopus, which has a nervous system entirely unlike a mammal or fish, feel when going about their day?
I read "progressive" as an ethical statement. Unless you can demonstrate a "scientific default" ethical system that all scientists should adhere to, this seems like valid distinction
Progressive means the scientists advocate reform or "new, liberal ideas". All of which is fine in their private capacity, but if these scientists are influenced in their scientific output by being progressive then they're not doing their job.
Many animals, e.g. tropical fish, have a four-dimensional color perception, compared to our three-dimensional one; thus making them easily distinguish colors that appear identical to us.
Some animals can also see polarised light
http://larouchepac.com/node/17209
Mantis shrimp can see the four linear and two circular polarization so the complete polarization picture. Oh and they have 12 color components. Oh and trinocular vision
"cats seem to lack guilt, they're not nearly as wired to be social"
Our Burmese cats actually do seem to be a bit guilty after they do something bad, also they are very social. Having said that, Burmese cats do have a reputation for being amongst the most dog-like of cat breeds.
I would say it is a mistake to assume either way without good reason. In some respect humans are very much like other species, and in other respects very unlike those same species. When we are around animals we inevitably feel a closeness that can cloud our judgement and make us assume motives that may or may not be there. It is bad science to assume the motives are what we feel they must be.
Even rats have empathy as proven in an experiment: http://www.wired.com/wiredscience/2011/12/rat-empathy/
We're about 80% the same as animals when it comes down to it. The difference is important, absolutely, but not as significant as you'd think.