As children develop, their capacity to comprehend parity and disparity becomes more sophisticated. For example, if you give a 4-year-old two small pieces of cake, and a 10-year-old one big piece of cake that amounts to the exact same amount, the 4-year-old will surely protest. No matter how hard you try to explain to the young one that two smalls equal one big, until you swap the plates, or surrep...
