As indicated in the introduction, a dominant hypothesis in the field is that there are various forms of impulsive behavior that may each contribute in unique ways to understanding addictions. This hypothesis emerged mostly because of descriptive differences between the purported subtypes (e.g., inhibiting an inappropriate behavior seems conceptually very different than reasoning about a delayed reward or risky outcome). Stronger evidence for this notion might include: 1) independent determination of individual differences in performance of various tests of impulsivity in both humans and animals, 2) unique relationships between each measures of impulsivity and addiction (i.e., each phenotype is predictive of or affected by exposure to drugs of abuse in dissociable ways) and 3) different underlying neurobiological mechanisms that configured each for of impulsive behavior.
