## 2 Materials and Methods  
For the purposes of experimental research, 4 versions of product packaging were prepared, which differed in the information presented on the front label: source of origin (plant- vs. meat-based) and the presence of health claims (high protein content vs. no such labelling). In order to maintain psychological realism and take the potential limitations presented in the literature review into account, meat patles were used as the examined product. On the basis of the prepared visualizations, an online survey was carried out on the Amazon Mechanical Turk platform among USA citizens who received small remuneration for taking part in the survey. Research was approved by the Poznan University of Economics and Business Committee of Ethical Science Research conducted with participation of humans--resolution number 13/2020, 27 December 2020. Participants were randomly assigned to one of 4 groups. During the study, after seeing a randomly selected 1 of the 4 versions of the product packaging (Figure 1), the participants provided their answers on a 7-point single-item scale (1--\"I strongly disagree\", 7--\"I strongly agree\") regarding: willingness to consume and assessment of the perception concerning the following product attributes: environmentally friendly, natural, high quality, healthy (Appendix A Table A1). Apart from questions related to the product, the participants provided answers about their socio-demographic situation. Additionally, in the trial, questions were included that allowed to check attention, excluding participants who spent less than 3 s observing the product, which could indicate insufficient familiarization with the product and as such could also have further impact on the reliability of the obtained results.  
Considering the above-mentioned exclusions, 522 respondents were included in the analysis. The mean age of the respondents (\(n=522\)) was 38 years (SD = 12.05, min = 19, max = 74). The group was dominated by men (54.78%). The most frequently declared level of education was bachelor's (57.66%), followed by master's (22.31%) and high school or equivalent (16.28%). Moreover, the group was diversified in terms of reported income (from below USD 19,000 to above USD 90,000). Within the context of meat consumption, the group included people with low and high levels of declared meat consumption, however, the majority of people stated their consumption level to be moderate or high levels (mean = 4.63; SD = 1.59), while the general attitude towards the burgers was higher (mean = 5.24, SD = 1.58).  
The data collected in the experiment carried out in 4 groups formed the basis for ANOVA 2 \(\times\) 2 analysis. In order to increase the credibility of the obtained results, bootstrapping was performed (\(n\) = 2000). Failure to meet the previously described requirements for the respondents' answers caused the number of participants in each group to be unequal in terms of normative standards, and amounted to: 148, 131,113, 130 individuals, respectively. Therefore, analysis of \(\chi^{2}\) was performed (\(\chi^{2}\) (4, \(n\) = 522) = 4.44; \(p\) = 0.21, which allows us to assume that the size of the groups was statistically equal, which is not a barrier for performing parametric analysis. A series of variance analyses was carried out to evaluate the effect of protein source and the \"high protein\" Nutrition Claim on product characteristics.