Beyond cigarette consumption, nicotine addiction also affects general cognitive functions and decision making processes, with for example, a tendency for smokers to prefer immediate small rewards over bigger, delayed ones. Numerous theories have been developed to model addiction, but an important framework states that addictive drugs modify the activity of dopamine (DA) neurons in reward signaling and in decision making. A powerful computational theory relies on unexpected reward for generating phasic DA release, which acts as teaching signals for appropriate learning and behavioral conditioning. In our lab, we have developed approaches in mice to investigate, from the molecular to the cognitive level, the mechanisms underlying nicotine addiction and of the resulting modifications of the decision making system and individual behaviors. We have dissected how nicotine, through its action on DA cells modifies different traits of an individual, from its reaction to stress, its social behavior or its exploration / exploitation balance. Addiction can thus be viewed as the result of a maladaptive decision process, but may also be considered as a particular and extreme situation illustrating the impact of DA dynamics modifications on personality.