Does ‘Common Sense’ Actually Exist?

The Conversation That Started It All Impact-Site-Verification: dbe0a4cc-465b-4744-8a67-cfcf8a94ff81

A few nights ago, I found myself on the phone with a good friend discussing something entirely unrelated when he casually dropped the phrase, “Well, it’s just common sense.” That simple remark derailed our entire conversation for the next 30 minutes.

I asked him to define what he meant by “common sense.” He couldn’t. Not really. He gave some vague examples, none of which were satisfying. The truth is, if you had to define “common sense” right now without consulting Google, could you? Try it. I’ll wait.

It’s surprisingly slippery for a phrase we all toss around like a verbal salt shaker. That conversation stuck with me, and after some late-night research rabbit holes and several internal debates about whether people are just born smart or taught well, I decided to investigate. Because let’s face it: many of us have probably wondered whether “common sense” is a real thing, or just a convenient myth we invoke when someone disagrees with us.

The Everyday Illusion of Common Sense

Ask a dozen people what common sense means and you’ll get a dozen different answers. Some say it’s “knowing not to touch a hot stove,” others define it as “being practical” or “not doing obviously stupid things.” And yet, the more you ask, the more it becomes clear: common sense is just a vague placeholder for “something I think everyone should already know.”

Psychologist Kenneth Hammond noted in his research that “virtually no one has convincingly described [common sense]” despite how often we use it (Dwyer, 2023). So why does this fuzzy concept endure? Probably because it’s comforting. If there’s a magical inner compass everyone should have, then people who make bad decisions must simply be broken. But reality is messier.

Aristotle’s ‘Sensus Communis’: Not What You Think

Let’s take a quick detour to ancient Greece. Aristotle introduced the concept of sensus communis, but it didn’t mean street smarts. It referred to the internal faculty that integrates input from our five senses into a single, coherent experience (Gregoric, 2007). You know, the thing that lets you tell the difference between a ripe banana and a rubber one.

Fast forward to the Enlightenment, and the term evolved into something closer to “natural reason” — the kind of thinking a farmer or a philosopher might use to solve a basic problem. But even then, it wasn’t assumed to be universal. That came later, with memes, talk radio, and exasperated parents everywhere.

High IQ, Low Sense? The ‘Clever Silly’ Paradox

Here’s where things get spicy. You might assume that smarter people have more common sense. But Bruce Charlton (2009) argues the opposite in his wonderfully titled essay “Clever Sillies.” According to him, high-IQ individuals often overanalyze situations, suppressing evolved instincts that might otherwise serve them well. In short, they’re too clever for their own good.

Need evidence? The Cognitive Reflection Test (CRT) famously asked Ivy League students a simple question: “A bat and a ball cost $1.10. The bat costs $1 more than the ball. How much does the ball cost?” More than half of students at Harvard, Princeton, and MIT got it wrong, answering $0.10 (the correct answer is $0.05) (Frederick, 2005).

So much for common sense being a side effect of elite education.

It’s the Speed That Counts: Processing Power Matters

If common sense exists at all, maybe it’s not a kind of knowledge but a kind of speed. A 2011 study by Coyle and colleagues involving nearly 7,000 adolescents found that increases in general intelligence (the famous “g factor”) were almost entirely mediated by faster mental processing speeds (Coyle et al., 2011). In plain English: smarter kids weren’t just better at answering questions. They were quicker at figuring things out.

This might explain why some people seem naturally “savvy” while others struggle. It’s not that they were born knowing how to fix a leaky faucet or dodge MLM scams. They just process problems faster, and perhaps more efficiently.

Recent neuroscience research supports this view. A 2021 study published in Nature Communications found that the brain’s white matter connectivity—essentially the neural wiring that determines processing speed—strongly predicts cognitive performance across various tasks (Karahan et al., 2021). This suggests that what we perceive as “common sense” may be partially rooted in the physical architecture of our brains.

The Learning Curve: Experience Trumps Instinct

Still, speed isn’t everything. Much of what we chalk up to common sense may just be learned experience. For example, a review by Strough et al. (2011) showed that 82% of 8-year-olds succumbed to the sunk-cost fallacy (throwing good money after bad), compared to about 50% of adults. We don’t pop out of the womb knowing how to make smart decisions — we learn it through trial, error, and ideally, a few embarrassing mistakes.

Further backing this up, Ritchie and Tucker-Drob (2018) found that every year of schooling increases IQ by 1 to 5 points. So even the intelligence we think of as innate can be shaped. Which means so-called “common sense” might be the result of uncommon learning.

This learning effect extends beyond formal education. Researchers at the University of Chicago found that expertise in specific domains dramatically changes how people perceive and solve problems, often making solutions appear “obvious” to the experienced that are anything but obvious to novices (Chi et al., 2014). What seems like common sense to a chef, plumber, or programmer is actually specialized knowledge gained through years of practice.

Cultural Relativity: Your Common Sense Isn’t Mine

Another wrinkle in the “common sense is universal” narrative: it varies dramatically across cultures. Anthropologist Clifford Geertz famously argued that common sense is not a static, universal faculty but rather a “cultural system” that varies from society to society (Geertz, 1975).

For example, in some East Asian cultures, it’s “common sense” to avoid direct confrontation to preserve social harmony, while in many Western contexts, direct communication is valued. Neither approach is inherently more sensible—they simply reflect different cultural priorities and histories.

A fascinating 2010 study by Henrich, Heine, and Norenzayan published in Behavioral and Brain Sciences found that people from WEIRD societies (Western, Educated, Industrialized, Rich, and Democratic) often make fundamentally different judgments about what is “obvious” or “natural” compared to those from non-WEIRD backgrounds (Henrich et al., 2010). This suggests that much of what we consider common sense is actually highly culturally specific.

Even the Robots Are Clueless

You might think AI would have cracked common sense by now, but not quite. Oren Etzioni, a leading AI researcher, once observed that while deep learning systems can beat humans at chess, they would keep playing even if the room catches fire (Thompson, 2018). That’s because AI still lacks the real-world context and flexible judgment we associate with human “sense.”

This AI limitation has even spawned dedicated research initiatives like DARPA’s Machine Common Sense program, which aims to develop AI systems that can understand and reason about the everyday world the way humans do (DARPA, 2019). The very existence of these programs underscores how challenging it is to define and replicate what we casually call “common sense.”

So if even supercomputers can’t do it, maybe we shouldn’t expect all humans to either.

So… Is Common Sense a Myth?

Kind of. It turns out that what we call “common sense” is really a cocktail of factors:

Cognitive processing speed

Learned experiences

Educational background

Cultural conditioning

Domain-specific expertise

Contextual awareness

It’s not so much a universal gift as it is a patchwork quilt of individual history, brain wiring, and exposure. Maybe that’s why it’s so hard to define. Because it’s not one thing. It’s everything.

A Quick Sense Check

Before you accuse someone of lacking common sense, ask yourself:

Have they actually encountered this situation before?

Is the answer as obvious as I think?

Would I have known this 10 years ago?

Am I mistaking my cultural assumptions for universal truths?

Could it be… that I am the one missing context?

If you thoughtfully considered all five, congratulations. You just used some uncommon sense.

References

Charlton, B. G. (2009). Clever sillies: Why high IQ people tend to be deficient in common sense. Medical Hypotheses, 73(6), 867-870.

Chi, M. T., Glaser, R., & Farr, M. J. (2014). The nature of expertise. Psychology Press.

Coyle, T. R., et al. (2011). Processing speed mediates the development of general intelligence (g) in adolescence. Intelligence, 39(2-3), 186-193.

DARPA. (2019). Machine Common Sense. Defense Advanced Research Projects Agency.

Dwyer, C. (2023). The problem with common sense. Psychology Today.

Frederick, S. (2005). Cognitive reflection and decision making. Journal of Economic Perspectives, 19(4), 25-42.

Geertz, C. (1975). Common sense as a cultural system. The Antioch Review, 33(1), 5-26.

Gregoric, P. (2007). Aristotle on the common sense. Oxford University Press.

Henrich, J., Heine, S. J., & Norenzayan, A. (2010). The weirdest people in the world? Behavioral and Brain Sciences, 33(2-3), 61-83.

Karahan, E., et al. (2021). Individual variability in the human connectome maintains selective cross-modal consistency and shares microstructural signatures. Nature Communications, 12(1), 1-15.

Ritchie, S. J., & Tucker-Drob, E. M. (2018). How much does education improve intelligence? A meta-analysis. Psychological Science, 29(8), 1358-1369.

Strough, J., et al. (2011). Decision-making heuristics and biases across the life span. Annals of the New York Academy of Sciences, 1235(1), 57-74.

Thompson, C. (2018). How to teach artificial intelligence common sense. WIRED.