At home alone with Peggy, I brought her from the living room to play in the bedroom while I worked there. Peggy had been playing with tinker-toy connectors of this sort (sketch of wooden cylinder with holes on the top, bottom, and around the side).
Even when I put her, sitting, on a multi-folded quilt, Peggy dismissed her block, ring tower, and rattle to play with this object. It was round and should roll. thrown onto the quilt, it did not roll much. Peggy threw it on to the floor and pursued it when it rolled. Most striking were those situations, they were frequent, when the piece landed on its flat side and did not roll at all. These clearly puzzled Peggy. She picked up the piece, put it in her mouth, tried again.

Relevance: Peggy may have solved this problem represented by this piece sometimes rolling and sometimes not. The incident suggests a clear experiment – give her two objects, of about the same size: a ball and a cylindrical solid, follow her experimenting with both to see if she can dependably get the cylinder to roll. Problem: how can we tell whether she has it figured out or not ? Does she lose interest ? Does she get it to roll consistently ?

Finally, this contrast, if still a puzzle to her, could be a situation where we could witness the mouthing “shape-verification” that Mimi believes she has seen.