What source can he give you? It's clearly a personal annecdote that is shared between a lot of people that use vim. What kind of source are you thinking about?
Not saying that this is a good study - I haven't even read it. Merely providing it as an example that at some point a study has been made in this area.
I'm not saying that you can't do it, you obviously can. It's just weird asking for studies for something that was clearly a personal annecdote. It's like asking someone: "Which knife is your favorite knife?" getting an answer and asking for a study that validates the answer.