A main goal of marketing is to evoke a sense of familiarity that enhance consumers' psychological and behavioural responses. Yet, little is known about why consumers sometimes respond negatively toward familiarity and respond positively toward novelty. Specifically, the question of how affective motivation drives consumers to favor novelty is important in achieving enhanced marketing. Interest or curiosity is an emotion related to a strong approach motivation and exploratory behavior toward novelty. This thesis explores the relevance and implications of interest to consumer psychology and behavior. The investigation is grounded in emotion differentiation, appraisal theories of interest, and a functional account of emotion. It draws from literature on the exposure effect, differentiation of positive emotions, the emotion of interest, metacognitive experience of fluency, new product and innovation management, and advertising.The thesis begins with a review of the relevant literature that shows how consumers tend to paradoxically favor both familiarity and novelty (Chapter 1). In this conceptual review, I propose that the differentiation between liking and interest can explain this previously unresolved paradox.Specifically, familiarity appears to evoke liking, whereas novelty elicits interest. This chapter contributes to our understanding of how and why consumers gravitate toward novelty by providing an explanation: consumers' have dualistic tendency to favor familiarity and novelty simultaneously.The remaining chapters present three streams of research which show that consumers tend to favor novelty because it generates the emotion of interest. Chapter 2 contributes to the innovation management literature by showing that consumers' subjective perceptions of novelty toward a product design, instead of the deviation of design itself, can enhance product evaluation and behavior toward the product. Chapter 3 contributes to the advertising literature by applying appraisal theories to the elicitation of consumer interest and demonstrates that the simple advertising cue of novelty can evoke the emotion of interest. Chapter 4 contributes to the literature on consumer research by showing that disfluency (i.e., metacognitive difficulty) can serve as a cue for novelty -one that evokes interest and enhances product evaluation. This provides a potential explanation to the conflicting findings between the positive effects of fluency (through familiarity) and disfluency (through novelty) on product evaluation.Taken together, this set of studies is the first to demonstrate the relevance and implication of interest to consumer psychology and behavior. I show that product design can benefit from considering the appraisal structure of interest and, specifically, it accounts for consumers' subjective perception and affective response toward design newness. I also find that a consumer's novelty appraisal is a significant determinant of perceived interestingness of an advertisement and this can be evoked by simple advertising ...