The more general approach to assessing personality variables in foreign policy decision-making is to ascribe the motivation of decision makers to their personality traits. By so-doing, certain variables external to the human elements but which act as boosters through which the personality elements influence foreign policy decision-making, are often ignored. Through a historical analysis of idiosyncratic effects on Nigerian leaders’ foreign policies, this article establishes that even though personality elements perform well as explanatory variables in foreign policy analysis, they do not solely explain the variance in decision outcomes. They require other factors to activate their expression as foreign policy determinants.