This article reviews a program of research on positivity and negativity effects in person perception. The focus is on studies in which perceivers receive information about the positive and negative behaviors of a target person (or group) and then make trait inferences. The research program was initially grounded in a theoretical approach based on trait-behavior relations (Reeder & Brewer, 1979) and then evolved toward a multiple inference model (MIM). According to MIM, perceivers make multiple inferences about the motives and traits of a target person (Reeder et.al., 2004). The rationale underlying this theoretical development is discussed in some detail.