Another point you could fix using intuition would be complete disinterest. It makes sense to put it at 0 on the [-1, 1] interval.
Assuming rational utility maximizes, a board that results in a disinterested agent would be:
Then each agent cannot influence the rewards of the other, so it makes sense to say that they are not aligned.
More generally, if arbitrary changes to one players payoffs have no effect on the behaviour of the other player, then the other player is disinterested.