Experts are especially prone to claiming they know more than they do

If you consider yourself a science buff, see if any of these terms seem familiar: meta-toxin, bio-sexual, retroplex. Ringing any bells? If so, you may be surprised to hear that these terms are entirely made-up. They are "trap items" invented to study overclaiming, the claiming of knowledge you could not possibly possess. If you overclaimed, you're not alone; one early study showed as many as one in five consumers have opinions on entirely imaginary products. Now, new research by Stav Atir and her colleagues suggests knowledge can be a dangerous thing, as those most confident about a topic are most likely to fall prey to this error.

Atir's team suspected overclaiming is driven by a "feeling of knowing": a generalised sense that we've seen something before, that we lean on in the absence of a true memory. This feeling can be led astray by our confidence. Imagine being certain that you know "biology stuff" and that you have some real biology knowledge. In this case, the genuine biology words in your memory – metabolic, retrograde, complex – give a ring of familiarity to made up biology-ish words like meta-toxin. Based on this reasoning, Atir and her colleagues predicted expertise in a field should lead to overclaiming, and set out to examine this in five studies involving 570 participants.

Each study asked participants to rate their familiarity with a series of items within a topic area (e.g. finance), some of which, like pre-rated stocks, were plausible but false. Across the first three experiments, the team found that people more knowledgeable in a given area – finance, biology, philosophy or literature – were significantly more likely to overclaim false knowledge in those areas. This relationship held after controlling for a "know it all factor" of their overall confidence in their general knowledge.

It could be that self-proclaimed experts are just trying to look good, and claiming familiarity they don't actually feel. To assess this, the fourth experiment added a condition that explicitly stated that some items were invented, giving a new incentive to the show-offs: to spot the fakes. After this warning, participants were warier, and in general more willing to choose the "never heard of it" option, but the higher rate of overclaiming errors by experts remained unchanged.

A final investigation suggested that while overclaiming may be influenced by an existing abundance of related concepts in a person's mind, it can also be produced simply by heightening a person's confidence in their knowledge. Participants took a quiz on US geography before the actual test of overclaiming (based on the same topic). When the quiz was constructed to be easy, giving participants the feeling they had a good grasp of geography, they went on to overclaim more. It suggests that merely feeling like an expert also sways our evaluation of ambiguous cues firmly towards the "seen it!" camp.

Minor overclaiming is likely quite common and harmless – remarking "I think I've heard of it" about the obscure foreign film you probably skimmed over when it was mentioned in The Guardian. More serious instances involve making claims or recommendations on more important issues, such as finance or health, areas where people often seek the advice of experts. Unfortunately, experts have a particular vulnerability that puts them at risk of overclaiming. This research shows this isn't simply a question of losing face: it can be difficult for experts to recognise when they are out of their depth.

Further reading

Atir, S., Rosenzweig, E., & Dunning, D. (2015). When Knowledge Knows No Bounds: Self-Perceived Expertise Predicts Claims of Impossible Knowledge Psychological Science, 26 (8), 1295-1303 DOI: 10.1177/0956797615588195