After each of the presidential debates, the media has scrambled to decide, among other things, which of the two candidates was more truthful. The fact-checkers worked hard, attempting to establish if anything President Obama or Governor Romney said was inaccurate. However, it isn’t as if the rest of us waited for the morning paper to make our own judgments. Whether watching the debates, viewing the commercials, or reading campaign literature, we always have a sense for how truthful a politician candidate is. Where does this sense come from?

Late-night television satirist Stephen Colbert urges his audience to rely on their gut for what he has dubbed a feeling of “truthiness.” Truthiness, Merriam-Webster’s 2006 word of the year, is “the quality of seeming to be true according to one’s intuition…without regard to logic [or] factual evidence.” Although Colbert deserves credit for coining the word, psychologists have long known that people rely on their feelings to draw all sorts of conclusions, and a recent paper clarifies one situation that seems to lead us to strong feelings of truthiness – the presence of additional related (but irrelevant) information.

The research finds that a statement in the presence of images or other additional information enhances people’s feelings of truthiness, even when they don’t provide any evidence the statement is true. This is especially important in the context of political campaigns, as it suggests that that the mere presence of a picture next to a candidate’s written claims could lead people to be more likely to believe them. And the work is another demonstration of the ease with which our thoughts, beliefs, and behaviors can be manipulated through relatively innocuous means.

The authors, researchers from Victoria University of Wellington , Kwantlen Polytechnic University , and University of Victoria , performed four experiments. In the first three studies, participants viewed names of celebrities, displayed one at a time. Some of the names also had a picture or a short verbal description attached. Finally, half of the participants judged the truth of the statement “this famous person is alive,” while the rest judged the truth of, “this famous person is dead.” The participants were more likely to judge a statement as true when it was accompanied by a picture or by a short description, regardless of whether the statement was that the individual was alive, or that the individual was dead. The effect was stronger for less familiar celebrities.

In a related experiment, the researchers showed the effect was not particular to celebrities. Participants viewed trivia statements, some of which were accompanied by related photos which provided no evidence of the truth of the statement, and indicated whether they thought the statement was true or false. For example, next to the statement “macadamia nuts are in the same evolutionary family as peaches,” a participant might see a picture of macadamia nuts. The photos increased the bias toward rating statements as true.

The fact that irrelevant pictures alter our perceptions of truth is related to a general principle about the way our minds work. Our judgments are based on not only the information we’re considering, but the way in which that information is processed and organized. The ease with which information is processed has long been known to lead to specific biases. The reasoning works as follows: when considering some piece of new information, an individual will attempt to remember other bits of consistent information. The more easily these bits of information are retrieved, the more likely the new information is going to be tagged as true. So, if you are told, “an ostrich’s eye is bigger than it’s brain,” you will attempt to recall all the information you know about ostriches, eyes, and brains. The easier you bring this information to mind, the more likely you are to decide that the statement is true (spoiler: it’s true).

This ease-of-recall is known as fluency, and the effect of fluency is extremely wide-ranging. While the present paper shows that we judge fluent information as more true, previous work has shown that fluently processed faces are judged to be more attractive , and fluently processed names more frequent . In fact, the Nobel prize was awarded to Daniel Kahneman 2002 for work which showed, among other things, that the ease with which we can bring information to mind leads to an assortment of biases in decision making.

Though the authors believe that this fluency explanation is the most likely one, it is impossible at this stage to rule out other explanations. The authors speculate that it is possible, for example, that the pictures or text could lead people to preferentially look for evidence consistent with the statement. For example, if presented with a photo of a celebrity, and the statement, “This famous person is alive,” one might seek out elements of the picture which provide support for the statement that he or she is alive, and ignore those elements of the picture which might suggest that he or she is not alive, like signs the picture comes from a previous decade. Further work should be able to disentangle which explanation is more correct.

With profound apologies to Colbert, these findings suggest we would all be wise to be more critical of our feelings of truthiness. Is that health claim on your cereal box accompanied by a picture? Do the safety claims of the car ad in your magazine appear alongside other information about the vehicle? Does the assertion of a fact on a website appear next to a photo of the writer? Given that we will live with the consequences of this presidential elections for the next four years, we should pay close attention not only to the information presented by the candidates, but also the manner in which they present that information. There are many instances in which trusting the truth which comes from your gut could mean that you’re subscribing to something less than the truth. In other words: if it feels good, question it.

Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook, a Pulitzer prize-winning journalist at the Boston Globe. He can be reached at garethideas AT gmail.com or Twitter @garethideas.