Final answer:
The phenomenon of a lottery winner not being any happier a year after winning is best explained by hedonic adaptation, which suggests that people tend to return to their baseline level of happiness over time, regardless of major life events.
Step-by-step explanation:
The situation described, where a lottery winner is no happier a year after winning a $10 million prize than before, is best explained by the concept of hedonic adaptation. This psychological phenomenon is the process by which individuals return to a baseline level of happiness despite major positive or negative events or life changes. According to studies such as those by Diener, Lucas, & Scollon (2006) and Brickman, Coats, & Janoff-Bulman (1978), after the initial excitement of winning the lottery wears off, the individual's level of happiness tends to return to what it was before the event.
This phenomenon is also reflected in the research of Lyubomirsky (2001), who discusses the role of cognitive and motivational processes in well-being and the idea that personal happiness is only partially influenced by external events. Therefore, the answer to the question posed by the student is a) Hedonic Adaptation.