Conjunction Fallacy

What is Conjunction Fallacy?

The conjunction fallacy is a common mistake in reasoning. Imagine that you’re given information about two options. One option is very specific with lots of details, and the other is more general. Even if it makes more sense to choose the general option, the conjunction fallacy is when you think the detailed option is more likely to happen. This error comes from our brains liking stories with more information, even if that information actually makes the story less likely to be true.

Another way to understand conjunction fallacy is by thinking about putting conditions on something. If you have one condition for an event to happen, that’s already a certain chance. But if you start adding more conditions, the chance of all of them happening together usually gets smaller. However, sometimes we forget this and think that the more conditions we add, the more specific and therefore, the more likely an event will happen. But that’s not the case – it’s actually the opposite.

How Does Conjunction Fallacy Affect Us?

The conjunction fallacy can sneak into our daily lives and color the choices we make. Here are some ways it can pop up:

  • Linda the Bank Teller: This classic example shows how the fallacy works. Due to the detailed description of Linda, including her background and activism, people are tempted to pick the more complex option because it fits a stereotype they’ve created in their mind. That’s why they think it’s more probable despite it being the less likely option statistically.
  • Health and Exercise: With this example, one can see how adding the detail of a healthy diet to regular exercise seems to complete the picture of a healthier lifestyle. This paints a more convincing image, so people are more likely to believe it’s more common, though being both a regular exerciser and a healthy eater is statistically less probable than just being an exerciser.
  • Job Candidate Assessment: Here, the combination of punctuality and hardworking traits sound like a better find in a candidate. Most people find this idea appealing because combining traits gives a fuller picture of an ideal employee, but this is a less likely combination than finding an employee with just one of those traits.

This kind of erroneous thinking can lead us to ignore good options or overestimate the chances of complicated scenarios. It could mean not hiring a suitable person because they don’t fit the ‘complete’ image of an ideal candidate or overestimating someone’s health habits because they exercise.

Dealing with Conjunction Fallacy

Learning how to avoid the conjunction fallacy can help us make smarter choices. Here are some tips:

  • Think in Terms of Probability: Remember that the more details, the less likely. Always ask yourself, “What are the chances of this happening?” and remember that adding details usually lowers the chance.
  • Break it Down: Look at each part of a situation separately. Check if you’re making the mistake of adding up things that should be considered on their own.
  • Learn the Basics of Statistics: Knowing some simple rules about chances and likelihood can help you spot when you might be fooled by too many details.
  • Reflect on Your Reasoning: Take a step back and think about why you find a specific option more attractive. Is it just because it’s more detailed?
  • Seek Contrary Evidence: Try to find reasons or proof that go against your first guess. This can help you see things from different angles and make a more informed choice.

By being aware of the conjunction fallacy and actively trying to think around it, we can get better at making decisions that are based on what’s actually likely, rather than what sounds good because it’s detailed.

Related Topics and Explanations

The conjunction fallacy doesn’t stand alone. It’s part of a wider web of biases and thinking shortcuts that can twist our judgment:

  • Representativeness Heuristic: This is about judging something by how much it matches what we think is typical. It’s linked to the conjunction fallacy because when we hear a detailed story that fits a stereotype, we might mistake it for being more likely.
  • Availability Heuristic: This happens when things that come to mind easily seem more likely. If specific scenarios are easier to imagine or remember, we may wrongly think they’re more common – this is how it relates to overvaluing detailed stories in conjunction fallacy.
  • Anchoring Bias: This is when the first bit of information we hear sticks with us and affects our decisions. In the context of the conjunction fallacy, if the first thing we hear is a detailed condition, we might anchor to it and believe it’s more probable than it is.

Why is it Important

Understanding the conjunction fallacy is crucial because it can affect all sorts of decisions in life. From choosing a job candidate to assessing health risks or deciding what to believe about people or situations, the fallacy can lead us down the wrong path.

For the average person, this means learning to question our first impressions and the tempting stories we hear that are full of specific details. It can help us avoid mistakes like investing in something just because it sounds promising with its specific conditions, or overlooking a good opportunity because it seems too simple. In essence, recognizing and working against the conjunction fallacy can make us wiser consumers, savvier decision-makers, and more rational thinkers in our everyday life.


The conjunction fallacy shows us an interesting quirk of human thinking – we often believe that more information means something is more likely, when in reality, it’s usually less so. Acknowledging this bias can lead to better judgment and smarter choices by encouraging us to look beyond the details to the actual chances of something happening. Understanding the conjunction fallacy, learning about it, and applying tactics to counter it are essential for everyone who wants to avoid the trap of misleading specificity and improve their decision-making process in all areas of life.