Abstract: This paper focuses on the effect of image number (less vs. more) on review helpfulness and explores the mechanism behind the effect. The current study tests the hypothesis through one field study and two laboratory studies. Study 1 is a field study. In Study 1, we collect 12,623 reviews of 56 brands in four product categories (hedonic-search, utilitarian-experience, utilitarian-search, and hedonic-experience) from www.jd.com. We use “likes” to represent review helpfulness, controlling “the time of review issued”, “the length of word review”, “the number of negative emotion words in word review”, and “the extremity of word review”, and examines how image number influences review helpfulness. Results of Study 1 show that image number influences review helpfulness significantly. The time of review issued, the length of word review and the extremity of word review all significantly positively influence review helpfulness. The number of negative emotion words in word review significantly negatively influences review helpfulness. Study 2 designs mocked camera websites including product introduction page and product review page. Study 2 utilizes one-factor subject design, and 245 participants attend Study 2. In less images condition, participants see six images relating to camera; in more images condition, participants see fifteen images. Results of Study 2 show that the main effect of image number on review helpfulness is significant. Image number significantly influences mental imagery and perceived product uncertainty, but influences perceived amount of information and persuasive effect insignificantly. In the relationship between image number and review helpfulness, mental imagery and perceived product uncertainty play parallel multiple mediating roles. In addition, the mediating effects of perceived amount of information and persuasive effect are excluded. To ensure the generalibility, Study 3 utilizes negative reviews of housekeeping service. The design of Study 3 is similar to Study 2, and the results of Study 3 replicate the findings of Study 2.

Key words: image number, review helpfulness, negative reviews, mental imagery, perceived product uncertainty