摘要:The current study examined the effects of volume and valence of user ratings in a movie rating Web site on individuals’ perception about the user ratings and also on individuals’ willingness to express their opinions online. In study 1, undergraduate participants were randomly assigned to one of 2 (volume: low and high) × 2 (valence: positive and negative) conditions. In study 2, undergraduate participants were randomly assigned to one of 4 (volume: low, high, super high, and mega high) × 2 (valence: positive and negative) conditions. The findings showed that individuals perceived others to be more affected by user ratings than themselves, that the perceived effect of user ratings on others was positively related to individuals’ willingness to express opinions, and that the extent to which individuals’ own rating differed from the valence of user ratings was positively related to willingness to express opinions in the negative valence condition, but negatively related to willingness to express opinions in the positive valence condition. This study applied social science theories to better understand the mechanism of individuals' opinion expression online. By manipulating user ratings about unreleased movies, this study controlled potential effects of participants' familiarity with rated movies.