As you might have heard, New York City is going to try to limit sodas served in restaurants to 16 ounces. How does 16 ounces translate to current soft drink sizes?
Take this quiz (New York Times Well Quiz) to find out whether you can judge the number of ounces from a picture of a cup. They say that one of the human development stages is being able to judge volume (with the classic beaker vs. graduated cylinder example), but I don’t know if I ever got the hang of it. My guesses were all wrong but I was close for the Burger King series. See how you do.
UC Berkeley's Student Dietetic Association 
I have no idea how to take that quiz… Oh well. I think in psychology last semester (or somewhere) they mentioned that more will get poured into wider/fatter cups/containers without people realizing it. (Hence, you should drink alcohol in a thinner glass or something like that….)