Mutual experience* presents a paradox.
*Mutual experience, simply put for purposes of this post, is doing the same thing as someone else. It could be simultaneous (e.g. riding a roller coaster with a friend) or temporally divided (e.g. reading a novel after a friend has read it).
There is little in life that is a more consistent source of pleasure than mutual beneficial experience. It explains the joy in reading old yearbook entries (where friends write of inside jokes) and the pleasure of jogging our memories with a friend or lover over a pleasant past mutual experience.** The pleasure of mutual experience is behind the nauseating (to me, but pleasing to many others) back-and-forth over travel experiences.
**It may be more than momentary. One study has shown that couples’ reminiscences of events of shared laughter improve overall satisfaction with their relations.