Scientists in New Zealand and Canada have found Stephen Colbert's concept of "truthiness" isn't just a late-night ruse to get laughs; the concept can also help explain how the human brain evaluates claims.

"We wanted to examine how the kinds of photos people see every day -- the ones that decorate newspaper or TV headlines, for example -- might produce 'truthiness,'" the lead researcher, Eryn J. Newman of Victoria University of Wellington, explained. "We were really surprised by what we found."

Colbert has explained that truthiness is "truth that comes from the gut, not books." In their study, published in Psychonomic Bulletin & Review, the researchers used the term "truthiness effect" to refer to a category of phenomenon where things that don't provide proof of a claim nevertheless caused people to shift toward believing that claim.

The researchers presented their participants familiar and unfamiliar celebrity names, half of which were currently alive and the other half of which were dead. The celebrity names either appeared with a picture of that celebrity or without one. One group of participants was asked to judge the truth of the claim that "this celebrity is alive," while another group was asked judge the truth of the claim that "this celebrity is dead."

When the claim was paired with a photo, the participants were more likely to judge that the claim was true.

"It is arguably unsurprising that photos inflated the truth of 'alive' claims: The photos depicted celebrities alive, and should have facilitated imagery of those celebrities doing various things -- all of which would be possible evidence of aliveness," Newman and his colleagues explained in their study. "The fascinating finding is that the same photos also inflated the truthiness of 'dead' claims: The photos did not produce an 'alive bias' but a 'truth bias.'"

In a separate but similar experiment, the researchers also showed their participants a series of general claims such as, "Turtles are deaf" or "The liquid metal inside a thermometer is magnesium." Like the previous experiment, the participants were asked to judge the truth of the claim, and some of the claims were accompanied by a picture. Newman and his colleagues found that the pictures produced a truthiness effect for these claims as well.

The study has important implications. For instance, it suggests that readers are more likely to believe that a story in a newspaper or on television is true if it is accompanied by photographs -- even if those photographs do not provide any evidence that the story is true.

"Decorative photos grab people's attention," Newman said. "Our research suggests that these photos might have unintended consequences, leading people to accept information because of their feelings rather than the facts."