by share certain similarities in that they both arise suddenly and momentarily. However, their following nominals show distinctive aspects, specifically, complements of at focus on the resultant states and those of by describe events. This paper argues that this difference is attributable to the schematic meanings of the prepositions. Although both prepositions express causality of momentary emotion, they have different schematic meanings, viz. target (at) and agent (by). Given the schematic meaning of target, the nominals following at are static and resultative. In contrast, since the schematic meaning of agent relates to dynamic changes, the complements of by describe dynamic situations. Based on the underlying assumption that the collocation patterns of at and by with emotion terms and following nominals are semantically motivated by their schematic meanings, this study examines at and by in three phases. The first phase comprises a qualitative analysis of historical data relating to the emergence of the schematic meanings of the prepositions; the second involves a corpus analysis, using the COCA to determine the emotion causality of prepositions and their conceptual rationale in emotion constructions synchronically; and the final phase consists of an experimental analysis to identify their different conceptualizations in emotion constructions.