Weeks ago now, I was walking on the trail by my apartment during what was basically the trail's rush-hour. That was entirely unintentional on my part. It's just that when I wanted to clear my head and take advantage of the nice weather happened to be the same time when lots of people were out on the trail, many of them heading home from work.
One such person was a Hispanic guy who looked like he was about my age and happened to start talking to me. It turned out that he was an immigrant who had only been in the country for a year, so his English was fairly broken. Since the only Spanish I know, I learned from Sesame Street ("Tu me gustas, that means I like you!"), there was a substantial language barrier, but we still somehow managed to have a fairly decent conversation.
Now, here's where context comes into play: before we started talking, I assumed he was a college student enjoying the nice weather, just like me. Likewise, he assumed that I was in high school and on my way home, just like him. No matter how hard I tried, I couldn't get across that language barrier that I was just out for a stroll, and that I needed to turn around to get back to my apartment before dark.
If he had just been out for a stroll, he probably would have caught on much quicker, but human nature seems to be that we assume everyone in a certain situation is there for the same reasons and in the same way that we are.
Come to think of it, I had a similar encounter in the elevator at the beginning of last school year. There was no language barrier this time, but a guy assumed that since I lived in the same dorm as he did, and since I lived on an Honors floor just like he did, I had to be a Freshman just like he was. It took me a bit to figure it out, because he was talking about "that class we have to take." As a Freshman, I probably would have caught on right away that he was referring to Honors Freshman Seminar. Just one year later, I had no idea.