First an initial guess at the minimax value must be made, possibly based on statistical information obtained elsewhere.
Then BNS calls search that tells whether the minimax of the subtree is smaller or bigger than the guess.
These results are analogous, respectively, to "prove best" and "disprove rest" heuristic search strategies.
[1] Experiments with random trees show it to be the most efficient minimax algorithm.
[citation needed] The default nextGuess function above may be replaced with one which uses statistical information for improved performance.