In poker, certain aggression plays like steals can be very effective; players must occasionally reply to them with defensive plays with hands they might not otherwise play. If, for example, an opponent to a player's right frequently steals when the player has posted a blind, the player can be reasonably sure that the opponent is often doing so with inferior hands (otherwise he wouldn't be doing it so often), the player can likely defend his blind (call or raise back) with more hands than he might otherwise.