About 20 years ago I had one of those wonderful moments when research takes an unexpected but fruitful turn. I had been studying toddler memory and was beginning a new experiment with two-and-a-half- and three-year-olds. For the project, I had built a small-scale model of a room that was part of my lab. The real space was furnished like a standard living room, with an upholstered couch, an armchair, a cabinet and so on. The miniature items were as similar as possible: they were the same shape and material, covered with the same fabric and arranged in the same positions. For the study, a child watched as we hid a miniature toy--a plastic dog we dubbed Little Snoopy--in the model, which we referred to as Little Snoopy's room. We then encouraged the child to find Big Snoopy, a large version of the toy hiding in the same place in his big room. We wondered whether children could use their memory to figure out where to find the toy in the large room.
The three-year-olds were very successful. After they observed the small toy being placed behind the miniature couch, they ran into the real room and found the large toy behind the real couch. But the two-and-a-half-year-olds, much to my and their parents surprise, failed abysmally. They cheerfully ran into the big room, but most of them had no idea where to look, even though they remembered where the tiny toy was hidden in the miniature room and could readily find it there.