^A The animal experimental literature is generally unwilling to call animals “addicts” and instead refers to their behavioral actions as “self-administering drugs.” As we will see later in the book, animals self-administer the same drugs that humans do, and animals self-administering drugs show most of the same behaviors that humans self-administering drugs do.

^B Ahmed and colleagues used saccharin in the water rather than sugar because saccharin has no direct nutritive value but tastes sweet to both rats and humans.

^C The Anonymous meetings (AA, Narcotics Anonymous, Gamblers Anonymous, etc.) and their 12-step cousins also include additional elements that seem to access important decision-making components. One example is the presence of a “sponsor” (someone you can call 24/7), who provides a low-cost option to pull one away from the high-value drug-taking option. Suicide hotlines also work this way, providing a very low-cost option (a phone call) that can short-circuit a dangerous path.

^D Why people prefer even dollar amounts is not known. Perhaps even dollar amounts are easier to calculate with. Perhaps people are suspicious of odd amounts because they are concerned that there’s a trick being pulled (like the extra used by American gas stations). Perhaps people can measure the even dollar amounts more easily, which may draw their attention. Whatever the heuristic, people do prefer even dollar amounts.⁴³