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The Problem With Common Sense

Thinking critically about the long-standing concept of "common sense."

In my youth, I came to understand the term "common sense" as implying that though you may not have extensive knowledge about a topic or even extensive skill in reasoning, you likely have enough of both to act appropriately in context (i.e., to "know better").

The first time I encountered the term, in a research context, was during my work on assessing credibility—a core aspect of the critical thinking skill of evaluation. The literature indicates that common belief and/or common sense statements (depending on the context in which they arise) are problematic in terms of being a credible source of information because there are no guarantees regarding their original source. Is the common sense based on experience? Anecdotal evidence? Flawed reasoning? Or actual research? And why is it common? It’s a bit of a lottery in that respect.

Common sense is common because many people are perceived to believe it. The problem is, that doesn't make it true. "Looks like a duck, walks like a duck" is common sense, sure, but consider "looks like a gator, walks like a gator." Lots of people confuse alligators and crocodiles. Why do so many people misspell "lose" as "loose"? Why do so many people say "literally" when they mean "figuratively"? 'Common' isn't a good enough criterion to make something true.

One of my favourite examples is that of seeing a couple walking down the street holding hands, where one person is rather attractive and the other is—well, let’s just say they’re "punching above their weight class". A common belief is that "opposites attract" and so we might apply that 'knowledge' through common sense because it’s relevant to the context and is a plausible explanation for the pair. However, research indicates that opposites do not attract. Coincidentally, it’s the opposite—similarity is a very strong predictor of attraction. As it turns out, the common sense statement, "birds of a feather flock together" is much more accurate. Of course, that information doesn’t fit the context here and so, had we used that, we’d still be left with a level of uncertainty regarding why these people are together. With that, it wouldn’t take too long to figure it out, had we spent a bit more time reflecting on it (e.g., the two are similar in respects other than physical attractiveness, hence the mutual attraction). But then, why would we bother? We have better things about which to think critically.

Not only can common sense be in opposition to research, it can be in opposition to other forms of common sense. Did you ever have a friend growing up whose household was run differently from yours (e.g., different rules and routines)? For example, in one friend's house, we could play in their parents' bedroom. Having never thought about the prospect in my own house, I figured it was common. When that friend came to visit my house and we went into all the rooms to play—including my parents’ room—I got yelled at: "You don’t bring friends into our bedroom! Where’s your common sense?" Maybe such 'sense' isn't necessarily common and is actually more personalised than one might think. This possibility shouldn’t be all that surprising. Consider again the interaction of base knowledge and the application of some reasoning on said knowledge. That knowledge may not be correct or contextually credible. If I were to believe some information as true (despite that not being the case (such as the appropriateness of non-family members in parents' bedrooms) and applied some reasoning to it, the result would still be ‘common sense’, even if it yielded a negative outcome. Where did I go wrong? I used my common sense!

An issue consistent with the above is false consensus, which refers to a cognitive bias where we overestimate the level of agreement people have with our views and perspectives. Our views, which we often mistake for factual knowledge, may actually be a minority view—making our common sense not so common. In reality, common sense may actually just be the rationale of a small group of people.

Moving on from the ‘common’ aspect of the term, let’s consider the sense part. If something makes ‘sense,’ it seems reasonable or logical: we’ll probably see a positive outcome. But that’s not always the case. Just as our knowledge can be suspect, so can that simple reasoning. A friend of mine was driving a few weeks back and narrowly avoided disaster after driving through a crossroads. He stopped at the sign, looked both ways, and, after seeing it was clear, took off. Unfortunately, it wasn’t clear, and thanks to the other driver’s evasive action, my friend avoided harm. His basic reasoning (if it’s clear: go; it is clear: so go)—was wrong. Had the reasoning been a bit stronger or more reflective (i.e., double-check because my view might be compromised), he would have avoided danger. Perhaps the problem with his application of common sense was that his knowledge and reasoning were not working adequately in tandem.

This brings us to one of the most explicit and interesting descriptions of common sense that I’ve seen in the research literature—as quasi-rationality. According to Cognitive Continuum Theory, reflective and intuitive judgments are considered poles on a continuum and, as thinking is never purely reflective or completely intuitive, all of our thoughts lie somewhere in between—a mixture referred to as this quasi-rationality (Cader, Campbell & Watson, 2005; Dunwoody et al., 2000; Hamm, 1988; Hammond, 1996). In this context, common sense is an adaptive form of thought, given that an individual may, on some occasions, reflect more on their judgments than through automatic, intuitive judgment, or, on other occasions, conversely rely more on the intuitive process. “Quasi-rationality has many advantages, which may be one of the reasons that the notion of common sense has persisted and been valued by the layperson for so long, despite the fact that virtually no one has convincingly described it,” wrote Hammond (1996).

I always found this particular description interesting because it accounts for both the knowledge source and the reasoning applied to it. However, by the logic of this quasi-rationality, essentially every form of thought is ‘common sense’ because no thinking is purely reflective or intuitive. In my interpretation, the recipe for the mixture is key. Intuition is experienced-based (i.e., a form of knowledge), whereas reflection is experience-based and reasoning-based, forcing you to take the time to think about the issue for a moment. Delay by even fractions of a second can increase the likelihood of decision accuracy (Teichert, Ferrera & Grinband, 2014).

Obviously, using common sense isn’t critical thinking, but it can be useful when critical thinking isn’t feasible or not worth the effort. However, for it to mean anything close to its colloquial use, it needs to be more than "going with your gut." There has to be adequate reflection to facilitate you in driving across a busy road.

With that, I’m interested in any research on common sense you may have encountered in the past. If you have such thoughts, please be sure to get in touch and let me know!


Cader, R., Campbell, S., & Watson, D. (2005). Cognitive continuum theory in nursing decision‐making. Journal of Advanced Nursing, 49, 4, 397–405.

Dunwoody, P. T., Haarbauer, E., Mahan, R. P., Marino, C., & Tang, C. C. (2000). Cognitive adaptation and its consequences. Journal of Behavioral Decision Making, 13, 1, 35–54.

Hamm, R. M. (1988). Clinical intuition and clinical analysis: expertise and the cognitive continuum. In J. Dowie & A. Elstein (Eds.), Professional judgment: A reader in clinical decision making, 78–105. Cambridge: Cambridge University Press.

Hammond, K. R. (1996). Upon reflection. Thinking & Reasoning, 2, 2–3, 239–248.

Teichert, T., Ferrera, V. P., & Grinband, J. (2014). Humans optimize decision-making by delaying decision onset. PloS one, 9(3), e89638.

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