They seem to consider the influence as the cause for similarity. Quoting from the end:
> They plan next to try the experiment in reverse: to scan incoming students who don’t yet know one another and see whether those with the most congruent neural patterns end up becoming good friends.
> They plan next to try the experiment in reverse: to scan incoming students who don’t yet know one another and see whether those with the most congruent neural patterns end up becoming good friends.