A parent comes to you for help to get her 15 year-old son “Tim” to clean his room.  Everybody (from advice columns in the newspaper to her church pastor) tells her that she needs to reward him for doing this job; but she is unsure about how to pick a reward.  What advice would Thorndike, Hull, Meehl, Skinner, Premack, Timberlake & Allison Response Deprivation theory, and Guthrie give about picking a reward for Tim?