Almost everybody does it when being photographed. I have been watching it for years, and recently began wondering how this became a part of Japanese culture. I have asked students and friends “why the peace sign,” but no one seems to know, so I did a small amount of research on my own. This is what I came up with.
In the late 1960’s it was prevalent in the USA during the Vietnam War. The “hippy movement” also caught hold to some of the younger people in Japan. In the early 1970’s American figure skater Janet Lynn was famous in Japan for giving the peace sign, and it has also been linked to a Japanese television commercial for Konika/Nikon cameras in 1972. The peace sign started catching on, slowly replacing the word “cheese.”
I must admit, it is contagious, and really does become a reaction when being photographed. I don’t know about other people, but I like “peace” better than saying “cheese.” It helps me smile too!