Don't tell me what I should do, but what others do: The influence of descriptive and injunctive peer norms on fruit consumption in adolescents
While healthy eating patterns are of high importance in adolescence, most adolescents portray quite unhealthy eating behaviour. One reason for this may be that social norms among peers tend to be unsupportive of healthy eating. The current study investigates whether communicating health-promoting descriptive and injunctive norms influences adolescents' intended and actual fruit consumption.
The study employed an experimental prospective design.
A norm message manipulation (descriptive vs. injunctive vs. no-norm control) was administered to high school students, after which fruit intake intention (N = 96) was assessed. At follow-up, actual fruit intake over 2 days (N = 80) was recorded.
Adolescents receiving the descriptive norm did not report higher fruit intake intentions than the control group, but did consume (borderline, p = .057) significantly more fruit in the following 2 days (2.3 portions per day) than the control condition (1.7 portion per day). Adolescents receiving the injunctive norm reported lower fruit intake intentions than the other two groups, but actual fruit consumption (1.5 portions per day) was similar to that of the control group.
Health-promoting injunctive norms not only had no positive effects on fruit intake but actually caused a decrease in fruit intake intentions, indicating that injunctive norms may be vulnerable to reactance. A health-promoting descriptive norm was found to positively affect fruit intake in adolescents. No effect on fruit intake intention was found. Results show that simple single-sentence norm messages hold the potential to substantially influence health behaviour.
Statement of contribution
What is already known on this subject? Previous research has shown that both descriptive and injunctive norms can influence behaviour. There are indications that for health behaviour specifically, descriptive norms may be more influential than injunctive norms. These previous studies have, however, been cross-sectional in nature.
What does this study add? The current study demonstrates that a very short and simple norm manipulation has the potential to substantially influence health behaviour. The current study demonstrates that injunctive norm messages have no influence on fruit intake, but a negative influence on fruit intake intentions, pointing to the potential that injunctive norms hold to induce resistance and reactance. The current study demonstrates that descriptive norm messages positively influence fruit intake behaviour, while intentions did not change, pointing to the possibility of descriptive norms functioning as heuristics for behaviour.