It is only logical to trust our instincts if we think we know a lot about a subject, right? New research suggests the opposite: self-proclaimed experts are more likely to fall victim to a phenomenon known as overclaiming, professing to know things they really do not.

People overclaim for a host of reasons, including a desire to influence others' opinions—when people think they are being judged, they will try to appear smarter. Yet sometimes overclaiming is not deliberate; rather it is an honest overestimation of knowledge.

In a series of experiments published in July in Psychological Science, researchers at Cornell University tested people's likelihood to overclaim in a variety of scenarios. In the first two experiments, participants rated how knowledgeable they believed themselves to be about a variety of topics, then rated how well they knew each of 15 terms, three of which were fake. The more knowledgeable people rated themselves to be on a particular topic, the more likely they were to claim knowledge of the fake terms in that field. In a third experiment, additional participants took the same tests, but half were warned that some terms would be fake. The warning reduced overclaiming in general but did not change the positive correlation between self-perceived knowledge and overclaiming.

In a final experiment, the researchers manipulated participants' self-perceived knowledge by giving one group a difficult geography quiz, one group an easy quiz and one group no quiz. Participants who took the easy quiz then rated themselves as knowing more about geography than did participants in the other groups and consequently were more likely to overclaim knowledge of fake terms on a subsequent test.

The results suggest that if you think you know a lot about something, you might want to double-check, lest you fall into the trap of skimming over words and concepts that seem familiar. In addition, the researchers point out that people who believe they know more than they do may be less inclined to pursue further education, or they may give advice about topics they do not fully understand. So the next time you are offered advice from a self-professed expert, you may want to take it with a grain of salt.