My experience is the opposite. Easy stuff is simpler to pair up. Really hard stuff is solo. E.g. I expect Ph.D. work to be mostly a solo project. Not that it's

My experience is the opposite. Easy stuff is simpler to pair up. Really hard stuff is solo. E.g. I expect Ph.D. work to be mostly a solo project. Not that it's impossible to do hard work collaboratively but I think a lot of heavy thinking is solo (Einstein, Newton e.g.) and it's hard to keep other people synchronized.