One of the clearest examples of how sensation and perception are different processes comes whenever you are transferring a substance from one container to another. How many times has this happened to you?
Last week, I was pouring myself my evening scotch. There seemed to be just a bit left in the bottle, so I figured I would pour the rest in. Much to my surprise, there were about 2 1/2 shots worth. I almost overflowed my cocktail glass. And no, I wasn't drunk. I only have one per night.
This morning, I was pouring my morning coffee and the same thing happened. There seemed to be just a little bit left in the pot. I almost overflowed my mug.
Similar things have happened with solids too. I have a dish that I usually use to grab a serving of nuts. It seemed like there was just about 1 serving or so left in the can. So I started pouring it in to my dish. Almost overflowed it.
I remember doing this with salt recently, but I don't remember the exact story. I think I was refilling my salt shaker from the canister.
There have been psychophysical studies that found people perceive more liquid in a tall thin glass than a short fat glass. It's not just that looks "can" be deceiving. They usually are.