= Unilateral deviation
{title2=$(s_i,s_{-i})\mapsto(t_i,s_{-i})$}
A <unilateral deviation> changes only one player's strategy, holding the other players' strategies fixed. It is profitable if it strictly increases that player's <payoff>, or <expected payoff> for <mixed strategies>. The comparison does not allow the opponents to adjust in response to the deviation. In a sequential game, however, holding an opponent's complete <pure strategy> fixed still allows their prescribed actions to differ after different observed histories.
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