Conjunction Fallacy

When we wrongly judge the conjunction of two events to be more likely than one of the events, when compared directly. A conjunction is the joining of two statements with words like 'and'.

• Scenario 1: Bob cares about his fitness and health.
• Scenario 2: Bob cares about his fitness and health, and runs frequently.

The conjunction fallacy occurs when we deem Scenario 2 to be more likely than Scenario 1, even though logically this cannot be the case (since Scenario 1 includes Scenario 2).

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Key Insights & Principles

Decision Making

1. More variables = less likely.
2. We are drawn to believe that more details in stories makes them more plausible.
3. More information often hinders our ability to clearly see that which is important to decision making.
4. The consideration of more variables in decision making makes us more likely to attach greater meaning or weight to unimportant details, and less weight to important ones.

1. When making decisions focus on the few important details.
2. Remove the unimportant.

Book References