Technological advances in products and systems have brought emotional design or emotional engineering to the forefront of research. While several measures to assess emotional expression of products have been developed, the source of the emotion rating of a product or system was often unclear. The purpose of this dissertation is to conduct three studies to examine the causes of emotional ratings and to establish if product-specific emotion rating scales are useful for capturing accurate user evaluations. Three studies were conducted using citrus juicers. Juicers were chosen for several reasons: their wide variety of styles, one self-explanatory purpose (to make juice), and the fact that their benign nature is unlikely to harm participants. Study 1 isolated juicers that had unique emotion profiles to use in the Study 2. Participants rated 41 juicers with fourteen product-specific emotions. Participants predominantly used "five" of the fourteen emotions in their juicer ratings. Ten juicers with the highest rating consensus, within these five emotions, were chosen for Study 2. Study 2 determined that anthropomorphic tendencies are predictive of emotional ratings. Extreme Anthropomorphism from the Anthropomorphic Tendency Scale (ATS) was used to test individual differences (Sims et al. 2005;Chin et al., 2005). Individuals with low anthropomorphic tendencies were more critical of the products. Sex differences also were analyzed, and significant interactions were found. Women exhibited different preferences for juicers than me. First impression ratings from Study 1 were validated by first impression ratings from Study 2. Finally, Study 3 measured the impact of product interaction on emotional ratings. Participants used seven juicers to make a minimum of four ounces of juice. Pre and post-interaction ratings were compared to determine the effect of interaction on the emotional appraisal of products. The results confirmed that interaction had an impact on affective ratings. As opposed to experienced users, novice users deviated in their pre-post appraisal, especially on aesthetically boring but highly usable products. Novice users based their entire initial appraisal on aesthetics, while experienced users were influenced by their past experience. Humans rely on past experience to recall likes or dislikes. The findings here suggest that aesthetic appraisal of products (or other environments) will remain influenced by past exposure/experience with those or similar products. Thus, only true novices can remain unbiased by past experience for aesthetic appraisal and capture a true 'first impression'. Also, past experience of users should be assessed when conducting research that relies on emotional appraisal of products. These findings may be especially useful in product development where new designs are based on a golden standard, competition, or go through several iterations of testing. The results may be used to guide human factors professionals to develop measures that more accurately capture affective ratings, and thus create more pleasurable products and systems.