Figure 1.

Trial sequence. First, participants were shown (for 3 s) a sentence and image that depicted a prosocial behaviour (in this example, “Raise money for charity”). They then rated how likely they would be to engage in that behaviour, using a computer mouse to move a slider on a visual analogue scale (Rating 1; no time restriction). Next, participants were shown (for 2 s) a screen saying either “Adolescents rated…” or “Adults rated…”, and were then shown a rating of the same situation, purportedly the average answer provided by a group of either adults or adolescents (2 s; this number was randomly generated). Finally, they saw a screen saying “Please rate again!” (2 s), and then were able to rate again how likely they would be to engage in that prosocial behaviour (Rating 2; no time restriction)