I experienced just how much language a dog can understand with a dog I had named Rowley. He was a mutt that followed us home.
We lived in NYC in an apartment, so he was walked several times a day but otherwise was confined to the apartment, so he got really excited when it was time for a walk. We used to say, "Whose turn is it to walk the dog?" and he would go berserk, running and leaping around excitedly. I figured it was because the walks happened at pretty much the same times of day, he'd see us get out his leash, etc.
But then we visited a friend with the dog, my daughter, and one of her school friends, who had just gotten a yo-yo and took it with her. A friend of the friend was there, too, and when he saw the little girl with the yo-yo, he asked her if she could do any tricks with it like "walk the dog." Immediately, Rowley went into berserk mode, programmed by those words to expect an outing. I was amazed, since it was totally out of context, and he must have actually understood the words, not just the circumstances.
Another weird thing I never did figure out was how he'd know we were reaching a destination. We'd go off to someplace in the country to hike on weekends, and Rowley loved being let loose to run back and forth on the hiking trails. Wherever we went, he would sleep in the car just until maybe 10 minutes before our arrival at the trail, and then he'd wake up all excited. I tried to figure out if it was the car slowing down after going fast on highways, or if our voices took on a different tone when we were close to our destination. I never could detect any signals that would let Rowley know we were getting close, but he detected them.
