The paper details three different experiments in which participants read about or actually performed a series of simple actions, such as shaking a bottle or shuffling a deck of cards. Then they watched videos of someone else doing simple actions - some of which they had done and some they had only seen being done.
Two weeks later, they were asked which of as many as 30 actions they had done themselves. Researchers found the subjects were much more likely to falsely remember doing an action if they had watched someone else do it.
Echterhoff says the research controlled for the common situation of thinking you had done something because you do it yourself every day. And, he says, participants had false memories even when cautioned about the possibility."