We love our dogs. In the 30,000 years humans and dogs have lived together, man’s best friend has only become a more popular and beloved pet. Today, dogs are a fixture in almost 50% of American households. From the way dogs thump their tails, invade our laps and steal our pillows, it certainly seems like they love us back. But since dogs can’t tell us what’s going on inside their furry heads, can we ever be sure?