1) When humans and dogs interact, both release "oxytocin" - also called "the hormone of love" which reduces stress. It is the same hormone that women release when they are breat-feeding. Scientist postulate that this is the reason why people with dogs are less likely to have heart-attacks and more likely to survive a heart-attack.
2) It only takes 25 years to create a new "breed" of dog. For example- the Dogo Argentino was created over 25 years to take down boars (without killing it) while able to be around children.
4) Dogs, like humans, read facial expressions from left to right (because we make expressions a-symmetrically). However, dogs to not read eachother's faces left-to-right and no other animal has been discovered to read faces in this way.
5) Studies have shown that dogs do not feel "sorry," but rather are expressing submissive behaviors in reaction to our reprimands. (For example, control groups of dogs also so "guilt" or submissive behaviors when they hadn't done something wrong.)
6) Dog-owners are able to tell the difference between six different dog barks (separation, strangers, hunger, playful etc...)
Source: Howstuffworks.com Podcast, "Does your dog really love you?"