from well.blogs.nytimes.com: How hard will your child work for food? In an experiment, researchers at Pennsylvania State University gave preschool children the opportunity to “work” for a food reward. All the child had to do was click a computer mouse four times to earn a cinnamon-flavored graham cracker. But earning additional treats required progressively more effort. A second treat required eight clicks. Then 16. Then 32. Some children were satisfied after one cracker, while others kept clicking for a few additional crackers. Most of the preschoolers were done after about 15 minutes, but some children stayed with it, accumulating as many as 2,000 clicks before the researchers ended the task after 30 minutes.