In the end, there aren't really that many differences between them; there is more variation from person to person then there is from subject to subject. Certainly the greatest difference I notice is one of passion; the good artists and the good engineers share a passion for what they do, and it's easy (for me) to talk to passionate people --- polite or no, passion is infectious and soon I don't care a whit about turn-taking or eye contact. The students who lack passion --- who are in engineering for the money or art because it's "easy" are the ones that make small talk.
I can't speak for the original poster, but I have taken both art and computer science classes. From what I have seen the eye contact issue is definitely a real force. Also I've noticed minor differences in body language, particularly hand movements when talking. It is hard to explain, as I am not a particularly talented people observer, but I have noticed that art students do talk with their hands in a different way than computer science students do.
