FREDERICK, MD–A Pavlovian response mechanism was triggered in Jamie Bolz Monday, when the 5-year-old reflexively shrieked at the top of his lungs upon seeing a large, colorful Toys 'R' Us sign during a family car trip. "Ahhhhhhhh! Toys 'R' Us! Toys 'R' Us!" Bolz involuntarily shouted despite countless lectures from his mother about proper car-trip conduct. Behavioral psychologists have likened Bolz's response to the well-documented Burger King-salivation reflex.