Truthiness: How non-probative photos shape belief

True or false? “A woodpecker is the only bird that can fly backwards”. When such a claim appears with a related, but non-probative photo (e.g., a photo of a woodpecker perched on a tree) people are more likely to think the claim is true - a truthiness effect. This truthiness effect holds across a range of judgments, including judgments about general knowledge facts, predictions about future events, and judgments about our own episodic memories. Throughout, adding a photograph to a claim rapidly increases people’s belief in that claim. We review the literature on truthiness, documenting the ways in which photos and other kinds of non-probative information can rapidly change people’s beliefs, memories, and estimations of their own general knowledge. We also examine the mechanisms contributing to truthiness and explore the implications for misinformation and fake news.