For example, level 3 develops what research indicates is a foundational cognitive building block of addition: Mentally combining two groups into one larger group—even before knowing the specific number. A customer orders two types of items, and children label these two collections in two separate boxes (e.g., two red triceratops and three yellow brontosauruses). The customer asks for one box
and children move all the dinosaurs into a new box (Fig. 2). They then label the new box with the sum (the Find Result level).