Cassidy is a teacher who loves to try piagetian questions on her young son. one day in the car she asked him who the fastest runners in his class were. to confirm she asked, "kevin is faster than bill, right?" and later she asked, "nate is faster than kevin, right?" waiting a while, she asked, "is nate or bill faster?" she smiled when her son said, "_____," because he was demonstrating _____.