Illusion of knowledge

"I am under the impression that I know and understand more than what I really know and understand."


The feeling of knowing or understanding something and the actual knowledge of that thing are not always related to each other. It is common, in practical and concrete everyday situations, as in more conceptual abstractions, to find that there is a more or less important gap between our real knowledge, and the perception that we have of it. The illusion of knowledge is a cognitive bias involving a person feeling as though they know more or understand better than what their actual knowledge allows them to assert [1]. In itself, the illusion of knowledge would therefore represent an erroneous metacognitive judgment, that is to say a bad judgment about one's own thoughts [2].


The practical, day-to-day use of a variety of devices (a zipper or a toilet, for example) may involve the feeling of knowing how such devices work. However, once questioned, it often happens that we are unable to explain them [3]. Similarly, a text can be read and give the impression of having been understood without any of the significant internal contradictions having been detected [4]. Our relationship with certain types of media, in particular those with a short, catchy and repetitive formula (“snack news”), can also induce a feeling of understanding, which does not, however, imply any proportional increase in factual knowledge [1, 5].


The illusion of knowledge bias manifests itself in different contexts and can be caused by different elements. A general cause of its manifestation would, however, be a lack of precision in the calibration of our real knowledge and of our perception of it [2]. A judgment regarding our knowledge of a given subject can thus often be made crudely, neglecting the extent of our incomprehension about the details and subtleties which compose this knowledge. In a media context, the bias could be explained by the frequent and general repetition of a topic, without its details being discussed. The repetition would help, among other things, create a habituation to the terms and subjects, the mention of which could no longer push us to raise questions (see the entry on repetition bias).

The quest for social approval is said to be another significant influencing factor in creating the illusion of knowledge. Being able to follow the trends of public opinion and being sensitive to the social importance of certain issues could indeed contribute to the mistaken evaluation of our real knowledge and to the reinforcement of the illusory but socially acceptable conviction that we understand these issues. [5].The bias could also be explained by presuppositions about how we think we understand or don’t understand something. For example, we might judge that we do not understand a text because of the unfamiliar words it contains and conversely that we understand a text that only contains familiar words. In the second case, even if the text shows logical gaps, we could still be under the impression that we understood it, simply because we were never interrupted by the need to search in a dictionary or think about complex concepts [4].


This bias can represent a significant obstacle to our learning process by impeding reflection on our own knowledge and preventing us from distinguishing what is known from what is not [2]. In a media context, the illusion of knowledge can also lead to consumer inertia in the face of certain issues that they feel they know well and for which they will therefore not seek relevant information that would otherwise motivate them to act [5]. Moreover, this bias could also be a significant influencing factor in the endorsement of more extreme political positions. Indeed, the illusion of understanding how certain policies work could pose an obstacle to their critical examination. Combined with other biases such as the Dunning-Kruger effect or the confirmation bias, the illusion of knowledge could thus contribute to political extremism [3].

Thoughts on how to act in light of this bias

  • Reflect on the causes of our judgments: is my judgment a strict endorsement of public opinion? Is it informed only by habit and repetition of the subject in question?

  • Opt to read full articles over reading several catchy titles.

  • Practice reasoning through causal explanations rather than listing reasons for your positions.

  • Stay humble about what you think you know.

How is this bias measured?

A variety of investigative tools are employed to measure the illusion of knowledge bias. Generally, these tools involve a reflection on the perceived state of our knowledge before and after a task measuring the current state of this knowledge [4]. In practice, participants are thus first invited to estimate their level of knowledge about a given subject. Then, carrying out a practical task relating to the subject in question (a knowledge test, a causal explanation, etc.) will make it possible to measure the difference between the actual knowledge of the participants and the previously estimated level. The illusion of knowledge is therefore calculated by looking at the gap between the actual and estimated knowledge of the participants [3, 4].

This bias is discussed in the scientific literature:

This bias has social or individual repercussions:

This bias is empirically demonstrated:


[1] Schäfer, Svenja (2020). Illusion of knowledge through Facebook news? Effects of snack news in a news feed on perceived knowledge, attitude strength, and willingness for discussions. Computers in Human Behavior, 103, 1-12.

[2] Kalamazh, Ruslana & Maria Avhustiuk (2018). Illusion of knowing in metacognitive monitoring: review of possible causes and consequences. Psychological Prospects Journal, 32, 109-122.

[3] Fernbach, Philip M., Todd Rogers, Craig R. Fox & Steven A. Sloman (2013). Political Extremism Is Supported by an Illusion of Understanding. Psychological Science, 24(6), 939-946.

[4] Glenberg, Arthur M., Alex Cherry Wilkinson & William Epstein (1982). The illusion of knowing: Failure in the self-assessment of comprehension. Memory & Cognition, 10(6), 597-602.

[5] Park, Cheong-Yi (2001). News media exposure and self-perceived knowledge: the illusion of knowing. International Journal of Public Opinion Research, 13(4), 419-425.


Individual level, Availability heuristic, Need for self-esteem, Need for cognitive closure

Related biases


Frédérick Deschênes, Master’s student in philosophy, Université du Québec à Montréal.

Translated from French to English by Cloé Gratton.

How to cite this entry

Deschênes, F. (2020). Illusion of knowledge, trans. C. Gratton. In E. Gagnon-St-Pierre, C. Gratton & E. Muszynski (Eds). Shortcuts: A handy guide to cognitive biases Vol. 2. Online:

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