How might a neuroscientist try to demonstrate that certain aspects of happiness are universal across all humans regardless of environment or culture?

A neuroscientist might use functional magnetic resonance imaging (fMRI) to show that some aspects of happiness are universal across culture and environment. fMRI allows a scientist to map which regions of the brain are active in real time, as a person is experiencing something or performing a cognitive task. 

The scientist could map the brain activity of a variety of subjects from different cultures while they are experiencing happiness. If the same areas of the brain lit up, this would indicate that at least some part of the experience of happiness is universal.

It would be important to frame the experiment to eliminate differences in culture. For example, it would be better to ask each individual to recall the happiest moment of their life and how they felt that day, as opposed to giving them a specific scenario (for example, a life event such as their wedding day) to recall, since different cultures may not experience life events in the same way.