Sample size calculation
In each randomized trial, participants responded to a first vignette without environmental factors and then, after randomization, a second vignette with or without environmental factors. To assess a mean difference of 1.0 for the outcome between groups on a scale from − 5 to + 5 with a standard deviation of 2.5, for each trial, a sample size of 264 was needed to detect the effect size of 0.4 with a power of 90% and α risk of 5%. Accounting for a 10% attrition rate, we required a sample size of 300 participants (150 in each arm) so that each vignette was evaluated 15 times in each arm.