Uncertainty Reduction vs. Reciprocity: Understanding the Effect of a Platform-Initiated Reviewer Incentive Program on Regular Ratings

Many e-commerce platforms have launched reviewer incentive programs, in which the platforms send free samples to experienced reviewers in exchange for feedback on the samples. This study focuses on an unexplored aspect of this practice: the impact of free samples on reviewers' ratings of subsequently purchased products (i.e., regular ratings). We theorize that free samples can increase regular ratings through two mechanisms: uncertainty reduction and reciprocity. We collect observational data from Amazon.com and find that after beginning to receive free samples from a platform-initiated reviewer incentive program (i.e., Vine), reviewers' regular ratings increased by 2.25% on average (i.e., 0.093 more stars on the five-star scale). Our follow-up analyses at a granular product-category level reveal that the increase in regular ratings occurs primarily for purchased products that share common attributes with free samples that reviewer has received previously. To further delve into the mechanisms at work, we conduct a randomized controlled experiment in which participants are asked to purchase one cookie among three flavor options. Before the cookie purchase, participants either receive nothing in advance (i.e., control group) or receive one of four free samples (i.e., four treatment groups). The results indicate that uncertainty reduction (via the common attribute between the free sample and the options for purchase) significantly mediates the impact of the free sample on the ratings of the purchased cookie. We conclude that platform-initiated free samples can help consumers understand products with similar attributes, thereby reducing prepurchase uncertainty and leading to higher regular ratings. We discuss the managerial and scholarly implications of the findings.