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

Many online platforms are now offering free samples to seasoned reviewers, hoping to get feedback. While these reviewers are given free samples to review, they also buy and review products themselves. The regular ratings for the purchased products are the majority. This brings up the question: Does receiving free products make them rate their personal purchases more positively? And if so, why? We explored two possibilities. First, uncertainty reduction mechanism : The idea that trying free samples makes buyers more confident in their purchases, leading to greater satisfaction and higher ratings for the purchased products; Second, reciprocity mechanism : The idea that reviewers might feel obliged to give better ratings as a “thank you” for the free samples or with the expectations of getting more free samples, which could introduce bias. Our research indicates that giving free samples mainly helps in reducing purchase uncertainty, making customers genuinely happier with their subsequent purchases. So, online platforms can benefit from this strategy, as it seems to uplift genuine positive reviews rather than create biased ones. However, it is still essential to monitor for any undue bias to maintain trustworthiness in reviews. 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