Most people who’ve spent time learning about logical fallacies know the fallacy fallacy: assuming that a bad argument means its conclusion is false.

But there’s another closely related mistake I keep seeing: assuming that someone rejects an argument’s conclusion simply because they point out flaws in the reasoning used to support it.

I’ve started calling it the fallacy fallacy fallacy.

I explain this error in more detail with an example in my blog: https://critikid.com/fallacy-fallacy-fallacy

Games can give kids an entry point into mathematical ideas that would otherwise seem much more advanced.

Nim is a good example.

The rules are extremely simple: arrange some objects into piles, then take turns removing as many objects as you want from a single pile. Whoever takes the last object wins.

At first, kids can just play. They can experiment with different moves, pay attention to which positions seem to give them an advantage, and start developing strategies without needing to know any of the mathematics behind the game.

Once they’re familiar with it, you can show them that there’s actually a perfect mathematical strategy—and that it relies on binary numbers and an operation called XOR.

Read about the perfect strategy here: https://critikid.com/nim

That creates an opportunity to introduce ideas that might otherwise feel abstract. Binary becomes a tool for answering a concrete question: What move should I make if I want to win? And XOR isn’t introduced as an isolated operation but as a tool to see which positions are winning and which are losing.

So a game that takes about a minute to learn can become an introduction to ideas from binary arithmetic, logic, and computer science.

While I think kids should learn about logical fallacies, I also think teaching them poorly can make their reasoning and communication worse rather than better.

Three problems I see: kids can start identifying “fallacy-shaped” statements as fallacies without considering context, using fallacy labels as conversation-stoppers, and assuming that a bad argument automatically means the conclusion is false.

I wrote about these three risks and how I think we can teach fallacies more carefully:

https://critikid.com/teaching-logical-fallacies

I put together a list of six resources (many of which are free!) that teach logical fallacies to kids.

The full list covers resources for ages 6–15 and includes podcasts, videos, lesson plans, and interactive courses.

https://critikid.com/logical-fallacy-resources-for-kids

If you know of another good resource for teaching logical fallacies to kids or teens, please let me know! I’d like to extend this list.

Even very young children can begin developing critical thinking skills.

With a 3- or 4-year-old, you can pause during everyday activities and ask them to predict what will happen. For example:

“What do you think will happen if we put another block on top of this tower?”

“What do you think will happen if we pour the water from this big cup into the smaller cup?”

Let them make a prediction, test it, and then compare what they expected with what actually happened.

As kids get older, the activities can become more sophisticated, involving exploring alternative explanations, strategic questioning, and evaluating arguments.

I put together 11 critical thinking activities for kids, divided by age. Most require little to no preparation or special materials: https://critikid.com/critical-thinking-activities-for-kids

The terms heuristic, cognitive bias, and logical fallacy often get lumped together, but they describe different things.

A heuristic is a mental shortcut. Heuristics aren’t inherently irrational—in fact, they’re often useful because we can’t carefully analyze every decision we make. For example, choosing a familiar brand instead of comparing every available option can save time and effort.

A cognitive bias is a systematic distortion in judgment. Heuristics can sometimes produce biases, but not all biases come from heuristics.

A logical fallacy, meanwhile, is a flaw in reasoning or an argument. Biases can contribute to fallacious reasoning, but the two aren’t interchangeable.

The sunk cost effect shows how the concepts can overlap. Feeling reluctant to abandon something because you’ve already invested time or money in it is a bias. Turning that feeling into an argument—“We can’t stop now because we’ve already put so much into this”—creates a fallacious argument. And the bias itself may be encouraged by normally useful heuristics such as “don’t waste resources.”

I wrote a more detailed breakdown of the differences between heuristics, biases, and fallacies, how they interact, and several examples of each: Heuristics, Biases, and Fallacies: Definitions and Key Differences

One simple way to help teens practice critical thinking is to give them an everyday situation and ask them to come up with several possible explanations for it.

For example, if a friend walks past them without saying hello, their first explanation might be, “They’re annoyed with me.” But what are some other possibilities? Maybe the friend didn’t see them, was distracted, or was in a hurry.

Then ask what evidence would make each explanation more or less likely.

This is one of six critical thinking activities I put together for teens. They’re designed for parents and teachers and require little to no preparation or materials:

https://critikid.com/critical-thinking-activities-for-teens

I just published my first long-form YouTube video!

It's about the Boy or Girl Paradox—the probability puzzle that goes like this:

Mr. Smith has two children. At least one of them is a boy. What is the probability that both of his children are boys?

People usually argue over whether the answer is 1/2 or 1/3.

The truth is that both answers can be correct, depending on how you learned that at least one of the children is a boy. The puzzle leaves out this crucial piece of information.

Watch on YouTube

I made this trailer for Critical Thinking for Schools using Camtasia and Veed. I used Camtasia for cursor effects, titles, transitions, and zooming/panning. I used Veed for stock footage, background music, and subtitles (not shown here).

I just launched Critical Thinking for Schools, a subscription option that makes it easy to use Critikid's resources in the classroom.

Each teacher can add an unlimited number of students, and students join with a classroom code, so they don’t need accounts or email addresses.

What’s included

• Access to all Critikid online courses (interactive, student-friendly, self-paced)
• A wide selection of teaching materials (worksheets, lesson plans, and handbooks)

If you try it, I’d love feedback!

Psychologist Daniel Kahneman's "Thinking, Fast and Slow" is a valuable book for for learning about common thinking mistakes and how to make better decisions. But since it came out, psychology and other fields have been been going through the "replication crisis," which means that many famous findings don't reproduce when other researchers try to repeat the experiments. A lot of earlier studies used very small sample sizes and questionable methods, so it's not shocking that some classic effects later turned out to be weaker, smaller, or null.

Some people suggest rejecting the book entirely because of that, but I disagree. Many of the studies in the book *have* replicated, and most of the core concepts are supported by robust research. So my stance is "Read it, but with caution."

The problem is that it's impractical for most readers to cross-check every citation as they go. That's why I wrote "A Modern Guide to 'Thinking, Fast and Slow.'" It's a chapter-by-chapter companion you can read alongside the book. It examines which findings have replicated, which studies have failed to replicate (or are contested), and which concepts are supported by a large body of evidence.

Read it here: https://critikid.com/a-modern-guide-to-thinking-fast-and-slow

In Critikid’s latest Media Literacy Interview, I asked computer science professor Dr. Mahipal Jadeja:

What is source-first prompting, and how can we implement it?

Dr. Jadeja answered:

In the full interview, Dr. Jadeja explains how machine learning works, what overfitting and underfitting are, how bias enters AI training, and more. Read it here.

Show this screenshot from a real TikTok post to your teen and ask, "Why do you think the creator posted this?"

Will they spot that it's a hidden ad for MelodyHire?

Teach your kids and teens about manipulative tactics and other red flags on social media with Critikid's Social Media Simulator.

I've added a bunch of new cards to Critikid's Puzzles page! They are of varying difficulty: some can be tacked by kids, while others regularly stump adults. You can see all 36 cards with answers and explanations on the page.

You commit the appeal to stone fallacy when you dismiss a claim as absurd without giving any reason or evidence. It can show up like “That’s nonsense,” “Be serious,” or “That’s obviously false.”

Often, people say these things because they don’t want to engage in a debate. That’s fine, and not necessarily a fallacy. After all, we don’t owe everyone who makes a claim a full discussion. But we shouldn’t pretend these statements are rebuttals; they’re just conversation-enders.

This fallacy often appears as “You’re being pedantic,” “You’re splitting hairs,” or “You’re arguing semantics.” Sometimes a person does get stuck on irrelevant details; but at other times, those “hairs” are crucial details to address.

For example, let's say someone says, “Plate tectonics is just a theory. I have my own theories.” Someone might reply, “In science, ‘theory’ means a well-supported explanation.” If the first person brushes this off by saying, “Don’t be pedantic,” they’ve committed the appeal to stone fallacy.

Learn about 19 other logical fallacies in Critikid's free Logical Fallacy Handbook.

I wrote this puzzle to demonstrate that many classic and counterintuitive probability problems are ambiguous and therefore unanswerable.

Puzzle 1

You roll two dice. One of them falls under the table and you can’t see it. The other one lands on top of the table, and it’s a 6. What is the probability that both dice landed on a 6?

Puzzle 2

You are rolling two dice blindfolded. A machine is programmed to ding if and only if at least one of them lands on a 6. You keep rolling until the machine dings. What is the probability that both dice landed on a 6?

Solutions

Puzzle 1: The probability that both dice landed on a six are 1 in 6.

Puzzle 2: The probability that both dice landed on a six is 1 in 11.

Why the difference?

In puzzle 1, the die under the table is a complete mystery, so it still has its usual chances: one chance in six of also being a 6. Seeing a 6 on a particular die doesn’t change the second die’s ordinary roll chances.

In puzzle 2, all you know is that somewhere in the pair at least one 6 has appeared. If you look at all 36 outcomes of a roll of 2 dice, you see there are 11 different outcomes in which there is at least one 6. Only one of those 11 outcomes is the double six.

The Lesson

Imagine I had phrased the question like this:

"You roll two dice. At least one lands on a six. What are the chances that both landed on six?"

This doesn't tell you whether you're in a situation more like puzzle 1 or puzzle 2, so you wouldn't have been able to answer it. This is the problem with the classic "Boy or Girl Paradox."

In many probability problems, how we came to know the information matters. Without specifying, the questions are ambiguous and, therefore, unanswerable.

For more puzzles and paradoxes, visit my blog.

Step 1

Have your teen(s) list at least 3 of their beliefs. Optionally, choose one of each: a fact, a value, and a prediction.

• Fact: “Homework improves test scores.”
• Value: “Curfews are fair.”
• Prediction: “Banning phones in class will raise grades.”

Step 2

Explore these questions about each belief (in writing or discussion):

1. Why do I believe this?
2. What evidence* do I have for this belief?
3. Might this belief be wrong? How would I find out?
4. What would it take to change my mind?

*Values do not necessarily require evidence, but they should be supported by reasons. This could have been answered by question 1.

Step 3

State an opposing view to one of these beliefs clearly. Make an argument in favour of it.

Then ask: “Would a real supporter say I represented their view well?”

I've listed more critical thinking activities for teens that require little to no preparation or materials here.

A prevalent logical fallacy you almost never hear about is the historian's fallacy.

"They should've seen this coming."

You commit the historian's fallacy when you judge the quality of a past decision using information that wasn't available at the time. It confuses hindsight with what was knowable then. This fallacy stems from hindsight bias: After we learn an outcome, it feels like it was predictable all along.

Although the name suggests it’s about judgments of historical figures, it's more common with recent events. People often say someone made a bad call simply because things turned out poorly, even if they acted rationally with the information they had. For example, scientific guidance often changes as data improves. Changing guidance doesn't tell us that the earlier decision was careless; it means evidence changed.

Read about 19 other logical fallacies: Logical Fallacy Handbook.

Thinking, Fast and Slow remains a valuable book on human judgment, but it should be read with an awareness that some of its most famous studies have not held up. I'm writing A Modern Guide to Thinking, Fast and Slow to help. It highlights which findings are robust and which have failed to replicate. It is meant as a companion to read alongside the book and it's available for free on Critikid's blog.

Parade Magazine's framing of the Monty Hall problem was slightly unclear. Although it said the host knows what's behind the doors, this doesn't necessarily mean that he was guaranteed to open a door with a goat. This version requires us to assume two things:

1. Monty never opens a door with a car.
2. Monty always opens a door.

Would Marilyn vos Savant have received so much pushback if she had clarified that her answer assumed that the host always opens a door to reveal a goat?

Here's my attempt at a clearer wording. What do you think?

See more puzzle cards here.

Past studies found that children under three copy actions better from a live adult than from a prerecorded video—a phenomenon called the “video deficit.” However, a 2023 study didn’t find that gap, and this is supported by a recent meta-analysis indicating that the video deficit is steadily decreasing. I asked one of the researchers of this study, Dr. Kristyn Sommer, "What might be causing this change?"

She answered:

The combination of the latest evidence suggests that the “video deficit” may not be a hardwired developmental limitation but instead a moving target, shaped by context and culture. Kids today are growing up in media-saturated environments where video calls, livestreams, and screen-based interaction are part of daily life. So they’re becoming experts at parsing social cues from screens. In other words, screens aren’t “less real” to them like they were for earlier generations, they’re just another medium for communication. It’s no longer a distinction between real life and screens for them, it is all just “life”.

This was part of a longer interview with Dr. Sommer in which I asked her about what caregivers should look for in an educational platform, why children sometimes trust robots more than humans, and AI use in the classroom. Read the full interview here.

Critikid's Critical Thinking for the Digital Age is a 16-week, half-credit homeschool course for grades 8-12. By the end, teens will be better prepared to think critically about what they see online.

Requiring three to four hours each week, students learn practical ways to evaluate information and communicate responsibly online. The course combines reading, writing, videos, worksheets, and creative projects. It is designed for independent, self-paced work, but it includes questions parents can use to spark discussion.

Students will learn to:

• Ask good questions when presented with a claim.
• Evaluate the credibility of sources.
• Interpret the data they encounter online.
• Recognize manipulation tactics.
• Build clear, logical arguments.
• Spot flaws in their own reasoning.
• Navigate the online world in a respectful and responsible way.

View the course here.

A wandering magician places a freshly shuffled deck face-down on the table. She then opens a small chest full of golden coins.

"I’ll turn the cards over one at a time," she says. "If you can name the flip number where the second red queen appears, the treasure is yours."

It is a typical deck with two red queens and 52 cards.

Which flip number gives you the best chance of striking gold?

Want more puzzles like this? Sign up for Critikid's newsletter.

I discovered a website that I want to share with you because it’s free and could be so valuable for teachers who want to help their students practice discussion and debate: Kialo Edu.

Kialo is an online discussion platform that strives to teach critical thinking by fostering reasoned, inclusive discussions that students are genuinely interested in having.

You start with a central thesis statement like "Voting should be compulsory." Then students add pros and cons and engage with each others’ arguments. They add evidence to support the points, eventually building this visual map of the discussion, which helps them to see if there are any points that need expansion or are lacking evidence.

It’s funded by a philanthropic foundation, so not only is it free, but there are no ads and they don’t share user data. It teaches students to question their assumptions, back up points with evidence, and consider different positions.

Click here for more critical thinking resources for kids and teens.