Background: This study tested the effect of social comparative norms on fruit intake intentions in students. We expected negative comparative information to increase intention and positive comparative information to increase or decrease intention (boosting or boomerang effect). Methods: Participants were 172 Dutch students (22% males, Mage: 21.9) who reported intention, attitude, self-efficacy and self-identity towards fruit intake. Fruit intake was reported during 3 days. Hereafter, they received a message that they either consumed more fruit than the average student (pos experimental group, n=46), consumed less fruit (neg experimental group, n=46), or received no message (pos and neg control groups, both n=40). Intention was then again assessed. Findings: Intention decreased among the neg experimental group (t=2.38, p=.02), while it stayed stable among the neg control group (t=-.15, p=.88). In the pos groups, the controls showed a decrease in intention (t=2.45, p=.02) while the experimental group stayed stable (t=-.15, p=.88). Discussion: Contrary to expectations, a negative comparative norm message demotivated participants to consume fruit, while a positive norm message seemed to boost intention. Hence, positive comparative norms seem most fruitful.
