This is why we should be eating off small plates at home and buying the small donuts instead of the regular sized one. You get more satisfaction for the same sized meal or equivalent satisfaction for a smaller one.
I admit to using smaller forks and smaller plates when I'm grabbing a quick meal for in front of the PC - makes the food look larger, and it's easier to handle, too.
Beyond just the magical thinker, I'd assume the restaurant didn't use both size glasses at the same time so no easily-available means for comparison existed.
