Ever since I took Psych 100 at Queens, I've had a fascination with describing people's quirks (very much including my own) with genuine--if pop--psychology. My stepfather and I had a discussion a while ago about the fact that I'm a clutterbug, and he attributed it to my being such a visual person that things are literally "out of sight, out of mind" for me (e.g. if I don't see my new box of highlighters, I will buy more on the assumption that I'm out).
This makes sense to me. I also tend to do this when grocery shopping, for instance buy 2 of something I have 3 of because it's a dry good and therefore lives in the back of my cupboard, but forget to buy milk even though I'm almost out because it's in the front of my fridge.
Anyway, I've been trying to remember what that's called, and I finally did, which is why I'm blessing all of you with this long-winded explanation. The Wikipedia article is short, so I'm going to quote the whole thing, more or less:
Object permanence is the term used to describe the awareness that objects continue to exist even when they are no longer visible.
Jean Piaget conducted experiments with infants which led him to conclude that this awareness was typically achieved at eight to nine months of age, during the sensorimotor stage of cognitive development. Such experiments consisted of behavioral tests with infant subjects. The infant would be shown a desirable object or toy, for example, and the toy would then be covered by a blanket or otherwise obscured from view while the infant was watching. Some of the infant subjects would immediately exhibit signs of confusion or dismay. Piaget interpreted these behavioral signs as evidence of a belief that the object had somehow 'vanished' or simply ceased to exist.
Piaget concluded that some infants were too young to understand object permanence, which would tend to explain why they cry when their mothers were gone ("out of sight, out of mind"). A lack of object permanence can lead to A-not-B errors, where children reach for a thing at a place where it should not be.