Explaining the Popularity Bias in Online Consumer Choice

When people choose products based on online reviews, they show a "popularity bias," overweighting review sample size relative to rated quality. We propose a novel account of this effect based on a causal attribution process, whereby people often interpret larger samples as a proxy for product quality. To test the account, participants in two experiments were asked to rate their product preference based on online reviews showing mean quality scores and review sample sizes for pairs of products. When no explanation for different sample sizes was supplied, we replicated the popularity bias; the product with the larger sample was chosen, even when quality scores modestly favored the alternative. However, as predicted, when sample size differences were explained by a factor unrelated to quality (e.g., time on the market), the popularity bias was substantially reduced. We discuss the implications for models of choice based on social information.