Almost any teacher will say: “in our school, we want students to become critical thinkers.” Once we embrace that praiseworthy goal, we’ve got some questions to ask.
How, exactly, do we help students think critically?
Or, here’s a bigger question:
Can we do that? Is critical thinking a skill that can be taught?
This debate frequently rages in educational circles.
- Team A says: “our society needs critical thinkers! Schools should teach this skill…here’s how.”
- Team Z says: “critical thinking isn’t a generic skill! People need knowledge with which to think critically…schools should teach that knowledge.”
I myself am sympathetic to Team Z’s claims. For instance, I’ve written a book about critically evaluating “research-based” claims in education. In that book, I repeatedly warn that I’m offering steps to think critically about this one topic; I’m not the right guy to think critically about the history of medieval Russia, or innovations in jet engine design, or a new rugby formation. I just don’t know enough about those topics to guide critical thinking about them.
I recently came across a study looking at this question. This study, helpfully, offers both reasons to be optimistic and reasons to be cautious. Here’s the story.
“Correlation Isn’t …”
A research team looked at 400 students taking college-level philosophy courses. About 115 of them took a course called “Critical Thinking”; the rest took other intro-level courses: “Introduction to Philosophy” and “Moral Problems.”
The critical thinking class focused on common biases or errors in judgment:
- mistaking correlation for causation
- honoring sunk costs
- ignoring regression to the mean
- forgetting about opportunity costs, and
- the gambler’s fallacy (“if a fair coin comes up heads 8 times, the next toss is REALLY likely to come up tails”)
The instructor began the course by offering obvious examples that intuitively resonated with students. Over the course of the term, students practiced applying the rules in many different contexts: athletics, romantic relationships, business, war, friendship, and so forth. The class interleaved these examples, and worked to ensure that students looked for the “deep structure” behind them. That is: rather than thinking “this is a claim about capital punishment,” the students learned to think “this is a claim about causation…I should be sure it’s not relying on correlational data.”
At the end of the course, students in the Critical Thinking class made ENORMOUS strides compared to the students in the other philosophy classes. The effect sizes ranged from 0.91 — well into the “large” range — to 2.01 — comfortably in the “I’ve never seen anything like it” range.
Let’s look at some raw data. For one of the fallacies — sunk costs — the control group and the critical thinking group both bought into a “sunk costs” logic at the beginning of the term. On a scale of 1 (“that’s not a good reason at all”) to 7 (“that’s a really good reason”), they gave a sunk-costs argument an average rating of 5.5. That is: they substantially agreed that “past investments should influence future decisions.” (“I’ve read half of this book, so I’ve got to finish it … even though I’m not enjoying it.)
At the end of the term, the control group continued to support this fallacy: they rated sunk costs reasoning at 5.5. The critical thinking students now dropped their average ratings to 1.4: very close to the “that’s not a good reason at all” end of the scale.
Even more impressive, those gains lasted. 25% of the enrolled students returned for a post-test sixteen months later. The effect sizes remained roughly 1.00 — a remarkably high number.
Technically speaking, this was quite a class.
Practicing What We Preach
Having seen the highlights of this critical-thinking study, let’s think critically about its methods and conclusions. A few points stand out.
First: students were not randomly placed in these courses; they opted in. Perhaps it’s unsurprising that students who signed up for a course called “Critical Thinking” improved at critical thinking. In other words: these students might differ in meaningful ways from students in the other courses.
A related point: these are college students taking philosophy courses. That’s a very select group within a very select group. As I’ve often argued, we should be cautious about applying college-student data to K-12 education.
Second: this was one course with one teacher. Maybe this study has identified an unusually effective professor.
Third: I gotta say, those effect sizes give me pause. A wise stats-y friend of mine says: “in education research, an effect size of greater than 1.00 is almost always suspect.”
Fourth: the post-test problems weren’t identical to the class examples…but they were structurally highly similar. We could plausibly call the results “near transfer,” but not “far transfer.”
Remembering Opportunity Costs
When I DO teach this novel, I’m NOT teaching that novel. That absence is the “opportunity cost,” and we should always be on the lookout for them.
In this case, I think we can say:
College students who opted into a critical thinking class got better at spotting four specific reasoning errors. (They didn’t get better at spotting the fifth — the gambler’s fallacy.) Their ability to spot those fallacies lasted an impressively long time: at least 16 months.
We don’t know if other professors are as effective as this one. We don’t know if such a course would work with younger, or with less interested, students. And — crucially — we don’t know if students got better at spotting those errors in their actual lives: when reading advertisements for timeshares, or evaluating claims by political parties, or making decisions about medical treatment.
For the reasons listed in the second paragraph, I worry about summarizing this study by saying “look, critical thinking CAN be taught”; instead, I think it arrives at a much more modest set of claims.
And: I worry about opportunity costs. I’m quite sure that students can’t think critically without substantial amounts of factual knowledge. I’m still unsure if students — even when they do well in a course like the one described above — actually think critically in real life. For that reason, I’m all in favor of talking with students about critical thinking; I certainly offer up examples of doing so in the classroom (and, I hope, on this blog). I’m still not persuaded that the time taken to teach a full course on the topic — especially to younger students — will accomplish our praiseworthy goal.
Bishop, M., Feltz, A., & Conway, P. (2026). Critical thinking classes can reduce common biases: Results from a field experiment. Journal of Experimental Psychology: Applied.
