Memory has long fascinated scientists. Researchers have already learned how to erase memories of fear, as well as how to plant false memories. Now, they want to erase all bad memories, at least those tied to drug addiction. Scientists looked at these particular memories because of how potent they are: drug cravings are triggered by something as simple as seeing a dollar bill or smelling cigarette smoke. The researchers began by creating a meth addiction in a group of laboratory mice who were trained to associate their addiction with certain sensory rewards.