Overestimating Stars, Underestimating Numbers: The Hidden Impact of Rating Formats

Some retailers use stars while others use Arabic numerals to present product ratings. Do consumers evaluate product ratings differently depending on the format? Which format more accurately represents the true magnitude of ratings? Across 12 experiments, we find that neither format is veridical. Consumers overestimate fractional star ratings (e.g., ) and underestimate fractional Arabic numerals (e.g., 3.5). The overestimation of graphical ratings arises from the visual-completion effect: When the visual system perceives an incomplete image of a star, it instinctively activates the complete image, causing consumers to anchor their magnitude judgments on rounded-up numbers (i.e., evaluation of is anchored on ). Importantly, our results show that this overestimation of star ratings can be mitigated by using visually complete stars (e.g., ). Conversely, the underestimation of Arabic numeral ratings stems from the left-digit effect, which leads consumers to anchor magnitude judgments on rounded-down numbers (i.e., evaluation of 3.5 is anchored on digit 3). Thus, both star and Arabic numeral ratings are systematically misestimated by consumers, with the extent of misestimation varying based on the fractional value and the star-filling technique employed. These findings demonstrate that prevalent rating formats are misleading, highlighting the need for new industry standards.