Greta Thunberg has been a great inspiration to many people, so much so that there is a supposed "Greta Thunberg Effect" — people who are familiar with Greta Thunberg are more likely to be engaged in climate action. But can a single person really make such a difference? A publication in the Journal of Applied Social Psychology put that question to the test. And, indeed, they found the Greta Thunberg Effect is real.