Imagine for a moment a mother and her four-year-old son in a busy shopping mall. She has to make three purchases and then get home in time to prepare supper. Her curious son has a different agenda. He is drawn to those counters loaded with the most alluring items--brightly colored basketballs, sporty race cars, a flaming red fire engine, even a pet store with an adorable Golden Retriever puppy wagging its tail in the window. Though Mom has a pretty good grip on her son's hand, she needs to use both hands occasionally, to handle merchandise, find a credit card, and to sign the purchase slip. So, at one of those times he manages to snatch free. She glances at him, assuming that he will stay close by until she can grab his hand again. But four-year-olds hold the Olympic record for the 5-mete…