Tania Lombrozo's newest post at NPR reminded me of a phenomenon I've often noticed: After going away on a trip for several days, when I return home it seems to me that my children have grown enormously over those few days!
It's not that they've actually grown, of course. My hypothesis is this: During my time away, my memory of my children grows a bit vaguer. Whereas my memory of them when I come home tonight might be an average of their appearance over the last few days, my memory when I come home after a week away might be an average of their appearance over a longer span of time -- maybe a month or two. Then when I return, they seem to have done a month's worth of growing in just that one week. The effect has been most striking during the periods my children have grown fastest (infancy to early childhood, and then my son's incredible middle-school growth spurt).
I'm not sure I'd test this hypothesis by drawing lines on the wall, as the researchers did in the article Lombrozo discusses. I suspect that my memory of my children's height is much more accurate than can be measured by wall markings -- e.g., that I'd easily notice an inch of growth, even if I might be off by several inches if asked to estimate their heights on a blank wall. A more valid measure, if it can be done right, might be to artificially age a picture by tweaking it slightly toward or away from the kindchenschema (the characteristic infantile facial features that slowly fade as we age).