The Smile Domino Effect

I walk down the main walk on my college's campus, and people look up, smile, wave if they know me. My aunt went to this college many years ago- and when I tried to tell her how people are so friendly here, she snorted in disbelief. "NO way. Not the same college as I went to." How did it change? Is it just the particular students in my year?

What gives a group its character? Who is the first person to smile at someone else, who then smiles at someone else, so on and so forth until everyone is actually nice to each other? If I had scowled at someone the first day, and that put them in a bad mood and they scowled at someone else...could that have broken the chain and now I would be living in a scowly, unfriendly enviroment? One of my own (unconcious) making?

How responsible are we for the enviroment we live in? And how much of it is out of our power?