The Dangers of Fluency

It’s a tale as old as time—it’s 2 a.m. the night before the exam and after rereading your notes for the tenth time during a last-minute cram session you finally feel like the material is “clicking.” You decide it is time to call it a night, only to arrive for the test the next morning and realize you can’t remember what you studied the night before. What went wrong? It’s likely that you were misled by fluency, specifically retrieval fluency. Retrieval fluency is the feeling that information is easy to recall, springing to mind without a lot of effort (Bjork, Dunlosky, & Kornell, 2012). Many people believe that retrieval fluency indicates learning because recalling something easily should mean that we’ll be able to recall it just as easily in the future. However, research indicates that conditions that increase retrieval strength tend not to increase storage strength (Bjork & Bjork, 1992). In other words, practicing in a way that makes recalling the information in the moment feel easy is not a good sign that you’ve learned that information in the long run.

Instead, research suggests that “desirable difficulties” (Bjork, 1994) tend to lead to better learning. Desirable difficulties are practices that tend to slow down improvement during studying or practice, but ultimately lead to better long-term retention of information. One such desirable difficulty that influences retrieval fluency is spacing, which involves several study or practice sessions over a long period of time instead of one massed session. In essence, spacing works because it gives us time to forget, something that is actually quite important for learning. Forgetting gives us an opportunity to relearn information, increasing the storage strength of that information and making it more likely to be recalled in the future. In a study of vocabulary learning, participants who used spaced study did better than participants who used massed study on a test a day later (Kornell, 2011). Spacing isn’t relevant to just students. One study found that postal workers learning to type out a new system of postal codes using spaced practice learned the system 15 hours faster than postal workers who used massed practice (Baddeley & Longman, 1978)!

Looking back to the beginning example, it is likely that spaced practice would have led to a better outcome on the test than a last-minute massed testing session, especially with the test still several hours away. It is also didn’t help that you were studying by rereading your notes, which is an ineffective study strategy. Rereading is passive, meaning that you don’t do a lot with the material while you read. A better way to use your notes is active restudying (Bjork, 2001). This could include reorganizing your notes, trying to recreate your notes from memory, or finding a study buddy to quiz you. Why is such an ineffective study strategy used by more than 75% of college students (Kornell & Bjork, 2007)? Well, rereading feels good: rereading doesn’t take a lot of effort and after a few times reading through your notes you feel like you know the material. This connects to a different type of fluency, called perceptual fluency. Perceptual fluency is the sense that something is familiar and easy to process (Bjork, Dunlosky, & Kornell, 2012). A classic study of perceptual fluency asked participants to memorize words in a big, easy-to-read font or in a smaller font that was more difficult to read, and then asked them the likelihood that they would be able to recall the words at a later time. Participants predicted that they would be able to recall the words in bigger fonts more than the words in smaller fonts, even though font size had no effect on recall (Rhodes & Castel, 2008).

Though relevant to education, perceptual fluency is also important outside of the classroom. One significant consequence of perceptual fluency is the mere exposure effect (Bornstein & D’Agostino, 1994). The mere exposure effect occurs when people come to prefer something simply because they’ve been exposed to it (Zajonc, 1968). Put simply, people tend to like familiar things. In a classic study of the mere exposure effect, participants were repeatedly shown Chinese characters so quickly that they could not be consciously perceived. When later presented with the familiar characters intermixed with new characters, participants showed an overwhelming preference for the familiar characters, even though they were unaware that they had seen the character before (Monahan, Murphy, & Zajonc, 2000). In another study, researchers had participants read a list of non-famous names. A day later, participants came in again and were asked to indicate which names were famous out of a long list of names. Non-famous names that had been studied earlier were significantly more likely to be selected as famous than non-famous names that weren’t studied (Jacoby, Kelley, Brown, & Jasechko, 1989)., Researchers were able to make a name “famous overnight” just by making participants familiar with it. Advertisers use the mere exposure effect all the time, hoping that by showing you TV commercials and billboards that your familiarity with their product or brand will make you more likely to buy their products.

Perceptual fluency has also seen increased attention with the accelerated spread of inaccurate information through social media and other sources. Targeted use of inaccurate information is not new: The tobacco industry used it in the 1970s and 1980s to discourage belief in the harmful effects of their products (Oreskes & Conway, 2010). The petroleum industry continued this practice in the 1990s to sow disbelief about climate change and weaken support for climate change mitigation measures (Walker, 1998). However, the popularity of social media has allowed information, correct or otherwise, to spread faster than ever before. Furthermore, social media allows people to see the same information multiple times, such as when multiple people in your social network share or otherwise interact with the same post. Unfortunately, a large body of work shows that people use inaccurate information even when they hold accurate prior knowledge (Marsh, Meade, & Roediger, 2003; Rapp, 2016; see Rapp & Salovich, 2018 for review). This can become problematic when people’s beliefs or choices are then based on information that isn’t true. Even more concerning, recent research indicates that repeated exposure to the same inaccurate information leads people to rate it as more accurate (Pennycook, Cannon, & Rand, in press). The sense of familiarity when people repeatedly read the same inaccurate statement is interpreted as “truthiness.”

So, what can we do to avoid being mislead by fluency? First, it is important to remember that fluency is not always misleading. In many cases, fluency is a useful heuristic to gauge our learning and characteristics of information. For example, when people are asked to study word pairs that are either related or unrelated, people correctly judge that related word pairs will be more recallable during a later test (Hertzog, Sinclair, & Dunlosky, 2010). Yet, there are instances when fluency can be used incorrectly. One way to avoid the pitfalls of fluency is to use desirable difficulties when studying. Space study sessions, test yourself, and work to actively study your notes, rather than just rereading. In everyday life, when you feel a sense of familiarity, question it. Ask yourself whether you want to buy the product just because it feels like the right choice, or if there’s a reason for your preference. On social media, think critically about information that “feels right.” Is it from a trusted source? Do you remember seeing that information anywhere else? When in doubt, fact-check. If you don’t trust a simple Google search, there are many great independent fact-checking sites available (e.g., PolitiFact, Fluency is a natural, and important, cognitive process. Actively engaging in your learning, in the classroom or otherwise, can help you recognize when relying on fluency is appropriate, and when you might need to rely on other cues.


Baddeley, A.D. & Longman, D.J.A. (1978). The influence of length and frequency of training sessions on the rate of learning to type. Ergonomics, 21(8), 627-635. doi: 10.1080/00140137808931764

Bjork, R. A. (1994). Memory and metamemory considerations in the training of human beings. In J. Metcalfe & A. P. Shimamura (Eds.), Metacognition: Knowing about knowing (pp. 185-205). Cambridge, Massachusetts: MIT Press.

Bjork, R. A. (2001). How to succeed in college: Learn how to learn. Observer: American Psychological Society, 14(3). Retrieved from:

Bjork, R. A., & Bjork, E. L. (1992). A new theory of disuse and an old theory of stimulus fluctuation. In A. Healy, S. Kosslyn, & R. Shiffrin (Eds.), From learning processes to cognitive processes: Essays in honor of William K. Estes (Vol. 2, pp. 35–67). Hillsdale, NJ: Erlbaum.

Bjork, R. A., Dunlosky, J., & Kornell, N. (2013). Self-regulated learning beliefs, techniques, and illusions. Annual Review of Psychology, 64, 417-444. doi: 10.1146/annurev-psych-113011-143823

Bornstein, R. F., & D’Agostino, P. (1994). The attribution and discounting of perceptual fluency: Preliminary tests of a perceptual fluency/attributional model of the mere exposure effect. Social Cognition, 12(2), 103-128. doi: 10.1521/soco.1994.12.2.103

Hertzog, C., Sinclair, S. M., & Dunlosky, J. (2010). Age differences in the monitoring of learning: Cross-sectional evidence of spared resolution across the adult life-span. Developmental Psychology, 46(4), 939-948. doi: 10.1037/a0019812

Jacoby, L. L., Kelley, C., Brown, J., & Jasechko, J. (1989). Becoming famous overnight: Limits on the ability to avoid unconscious influences of the past. Journal of Personality and Social Psychology, 56(3), 326-338. doi: 10.1037/0022-3514.56.3.326

Kornell, N. (2009). Optimising learning using flashcards: Spacing is more effective than cramming. Applied Cognitive Psychology, 23, 1297-1317. doi: 10.1002/acp.1537

Kornell, N., & Bjork, R. A. (2007). The promise and perils of self-regulated study. Psychonomic Bulletin & Review, 14(2), 219-224. doi: 10.3758/BF03194055

Marsh, E. J., Meade, M. L., & Roediger, H. L., III. (2003). Learning facts from fiction. Journal of Memory and Language, 49, 519-536. doi: 10.1016/S0749-596X(03)00092-5

Monahan, J. L., Murphy, S. T., & Zajonc, R. B. (2000). Subliminal mere exposure: Specific, general, and diffuse effects. Psychological Science, 11(6), 462-466. doi: 10.1111/1467-9280.00289

Oreskes, N., & Conway, E. M. (2010). Defeating the merchants of doubt. Nature, 465(10). doi: 10.1038/46586a

Pennycook, G., Cannon, T. D., & Rand, D. G. (in press). Prior exposure increases perceived accuracy of fake news. Journal of Experimental Psychology: General. Retrieved from:

Rapp, D. N. (2016). The consequences of reading inaccurate information. Current Directions in Psychological Science, 25, 281-285. doi: 10.1177/0963721416649347

Rapp, D. N. & Salovich, N. A. (2018). Can’t we just disregard fake news? The consequences of exposure to inaccurate information. Policy Insights from the Behavioral and Brain Sciences, 5(2), 232-239. doi: 10.1177/2372732218785193

Rhodes, M. G., & Castel, A. D. (2008). Memory predictions are influenced by perceptual information: Evidence for metacognitive illusions. Journal of Experimental Psychology: General, 137(4), 615-625. doi: 10.1037/a0013684

Walker, J. (1998). Draft Global Climate Science Communications Plan [Memorandum]. Global Climate Science Team. Retrieved from:

Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of Personality and Social Psychology Monograph Supplement, 9(2, Pt.2), 1-27. doi: 10.1037/h0025848