[kentlyons]

It wasn't entirely clear from this article, but the intervention itself is the scavenger hunt and associated instructions. From the supplementary material: "Participants in the treatment condition were asked to talk to the person for at least a couple minutes, whereas participants in the control condition were simply asked to observe the person for at least a couple minutes". And from the related work this is based on previous research: "This suggests a promising intervention strategy: give people concentrated and repeated practice talking to strangers, so that they may realize their fears are exaggerated."