Addiction: The physical and mental state of dependence on a substance or stimulus, to the point where withdrawal symptoms occur whenever the substance is not present in the body.
Explanatory Style: How individuals describe their successes and failures to others, indicating an optimistic or pessimistic bent, which researchers believe tells much about the teller's psychological state.
Genetic Variability: The biological reality that offspring of any given species will differ from its parents, and that some offspring will survive by adapting to changing conditions.
Motivation: The process of starting, directing, and maintaining physical and psychological activities; includes preferences for one activity over another and persistence of responses.
Phobia: An intense, irrational aversion to something; an overwhelming fear of an objectively harmless stimulus that interferes with normal functioning.