Social norms and climate-friendly behavior of adolescents

the corresponding coefficients, showing the treatment effects for Grade 8 (age 13/14, in medium turquoise), Grade 9 (age 14/15, in light green), and Grade 10 (age 15/16, in dark purple). For the empirical expectations, we replicate the results from the aggregated analysis. The treatment information HIGH did not alter students’ empirical expectations, regardless of age, while LOW shifted the empirical expectations in all age groups (statistical significance: p<0.01 for Grades 8 and 10 and p<0.05 for Grade 9). For the normative expectations, similar to the overall analysis, we found that the treatment interventions did not influence students’ percep- tion for Grades 9 and 10. However, the younger students in Grade 8 were significantly influ- enced by the information of the LOW condition and evaluated small and medium donation amounts as more socially appropriate than students in CONTROL did (p<0.1 for small and p<0.05 for medium donation amounts). The greater susceptibility of Grade 8 students is also reflected in their donation behavior: While the older students did not change their donation decision in response to the treatments, the eighth graders slightly increased their donations when treated with the HIGH information (p<0.1) and significantly reduced their donations when treated with the LOW condition (p<0.05). We suggest two possible explanations for the age-specific effects of social norms: (i) those in older age groups adhere more to specific peers than to their general age group, and/or (ii)

the older students have stronger established personal normative beliefs. Evidence supporting the latter includes the fact that self-reported climate-friendly behaviors are a strong predictor for the donation decision in Grade 10 and that participation on Fridays for Future protests was significantly more common in Grades 9 and 10 than in Grade 8 (p<0.01; see Table B.10 in S1 File). We will return to these points in the Discussion. Discussion and conclusion In this study, we experimentally manipulated the information adolescents between 11 and 17 years old received about the (lack of) support of other young people for climate protection. We operationalized climate protection as a donation to a CO2 offsetting scheme and systematically assessed how information about previous low or high donation amounts made by peers of the same age influenced (i) adolescents’ beliefs about their fellow students’ donation behavior (empirical expectations), (ii) adolescents’ beliefs about how their fellow students ranked the social appropriateness of small and medium donation amounts (normative expectations), and, lastly, (iii) how the information influenced their own donation decision. With regard to the different types of information, our study confirms a finding of previous social norm studies with adults: Individuals react more strongly based on information about others’ behavior when the described behavior is in line with one’s self-interest [43, 48]. In our case, this was the information that other students of the same age and from the same type of

school and city had donated small amounts to climate protection. In response, the adolescents significantly lowered their expectations about how much their schoolmates of the same grade would donate. Beyond this, however, we found no effects on normative expectations and actual behavior. Contrary to our hypotheses, students, on average, did not alter their donation behavior in response to the treatment information. One may argue that this is due to our subtle treatment manipulation—showing exemplary donations on a donation receipt is a relatively discreet way of conveying information about others’ behavior. However, we deliberately chose this subtle method to prevent students’ align- ing their donation decisions to the information simply because they believe this is what we as experimenters expect of them. In addition to the general caution towards social desirability bias [60] and against inducing experimenter demand effects [59], it has been shown that PLOS ONE Social norms and climate-friendly behavior of adolescents PLOS ONE | https://doi.org/10.1371/journal.pone.0266847 April 27, 2022 11 / 16