It's one of those things that everyone knows they should be better at than they are. After a meal, you stand there in the kitchen, eying the food remaining in the pot and contemplating your cabinet full of oh-so-conveniently-sized blue-lidded Ikea plastic containers. If you're anything like everyone else, the container you grab, however, is inevitably much too large for the amount of food you have to put in it. "Oh, that looked like more," you grumble as you press down the lid and stick it in the fridge (which is quite possibly already overflowing with half-filled plastic containers from other nights like this).
This is pathetic. Why can't well-educated, otherwise functioning adults make simple volume judgments? According to Piaget, this is the sort of behavior one should expect from someone in the preoperational stage of development—from ages two to seven! (Piaget had two short, fat beakers filled with the same amount of water, then poured the water from one beaker into a tall, thin beaker, and small children think the beaker with the higher water level has more water.) Now, obviously we are slightly more sophisticated than these two-to-seven-year-olds, since we would, having watched the contents being transferred, know intellectually that they were the same. However, presented merely with the two different containers, we would likely judge them to contain different amounts. The problem is that we apparently lack the skills to judge how much volume a certain amount will fill when its shape is changed. This is not only inexcuseable but somewhat surprising. How are volume judgments not important enough evolutionarily for them to stick?
The good news: it is possible, though extensive training, to master the formidable art of leftovers-packing. I should know, for I have conquered. Behold: the goddess of food volume judgments!
By "extensive training," of course, I basically mean paying attention. I was kind of surprised that one day I just decided, "This is pathetic. I am smarter than Ikea plasticware," and then I suddenly had acquired this ability. Seriously. The first and only real step is just always to select a container smaller than the one you think you need. I have yet to actually run out of container before I ran out of food.
I'm wondering if I will ever not be amazed at my newfound skill. Also, how long it will take for my roommate to get really fed up with my prancing about the kitchen in triumph...