The spread of false information (e.g. fake news, gossip, secrets) in social media has caught a great deal of attention by both academic research and popular news. Importantly, it has been shown that most people do not share misinformation to hurt others but to gain personal benefits that reinforce their well-being, status or political beliefs. In other words, misinformation has a self-perpetuating nature, which sparked interest in identifying measures that reduce its dissemination. The dominant measures proposed are linked to the use of verification. The underlying assumption is that if information is easy to identify as false, most individuals will not disseminate it. We test this assumption through a controlled online experiment. We vary how individuals verify the truthfulness of the information they receive in three conditions: no verification, exogenous verification (individuals are forced to verify) and endogenous (individuals can choose to verify or not). Our results show the conditions under which verification is e↵ective in preventing the spread of lies in social networks. In particular, we find a positive but moderate e↵ect of verification. It reduces lying but only to a certain extent. Moreover, the strongest e↵ect comes from endogenous verification, where individuals choose whether to observe information that may go against their material interest. Finally, the role of verification influences a shift in who is responsible for lying. While in networks without verification the liar can be in any position, in those with verification lying is shifted to the final players.