So why does hearing the theme music of Super Mario Bros. or catching a whiff of something that smells like an old arcade help to bring us out of a funk and lift our spirits when we have no way to recapture the original experience? Well, it seems that nostalgia isn’t just about the place or the thing. “On a basic level, recalling these positive memories simply puts us in a more positive mood,” explains Cordaro. “On a more complex level, recalling these experiences makes us feel a stronger sense of social connectedness with others. We’ve done some research looking at what people usually describe as a ‘typical nostalgic experience’ and find that people typically think about positive experiences in which the self is the protagonist, but they are surrounded by and interacting with others.
— Interesting coverage in Edge of an article in social psychology about nostalgia