Steemit Logic Comic (Pt.4) - Conjunction Fallacy

This fallacy assumes that having multiple conditions or variables produces a more probable outcome, compared to only one condition or variable being less likely to happen. Though the opposite is true.

Steemit Logic Comic

It's called a conjunction because of the conjunction of two conditions giving the impression that they are more likely. Perhaps people think having more things together is better. The thinking is that a greater quantity of variables, objects, or events leads to a greater quantity of probability. More is better, right? LOL.

source

The reality is that a condition alone is more likely, while each additional condition decreases the probability of the outcome happening. The more requirements you need, the harder it is to meet them.

No matter how unlikely something alone can happen, it's still more likely to happen alone, than to happen "and" something else happening as well.

The above image shows it clearly. The area for A, B or C alone is largest. While the area of the conjunction between AB, AC or BC is smaller than the single areas, but is larger than the final level conjunction of ABC that has even less area. This is how the probability of conjunctions and the conjunction fallacy work.

Taking the probability of one thing, and adding another, can't produce a probability greater than each individual. It can only be less probable. The conjunction of conjuncts might seem more likely to be a realistic scenario given how it adds detail and can be more easily imagined, but that's not how it probability works...

The classic example is:

Linda is 31, single, outspoken and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice and also participated in antinuclear demonstrations.

Which is more probable?

1. Linda is a bank teller.

2. Linda is a bank teller and is active in the feminist movement.

86% of people in some tests say option 2 is more likely.

source

But the reality is that Linda simply being a bank teller alone is more likely than her also being something else in addition, even if that something else matched the earlier description more. There is a representativeness heuristic bias of reading the description that affects how we choose between the options, tricking us.

People generally don't think of the outcome in terms of probability, but only as two alternative options. Either something is true because of 1 factor, or its true because of two factors. But instead of thinking of the options as polar opposites or dichotomies, the two options should be seen as subsets. One as a child and the other as a parent, or specific to general, particular to universal. Bank teller is first, then the subset is being in the feminist movement.

If option 1. would say Linda is in the feminist movement instead, then that would have been the more probable answer. It would be singular, individual, particular and specific, like Linda is a bank teller. The second option adds more conditions, making it more specific and less likely. This is another perspective that the individual/universal or specific/general duality plays out. I have covered others aspects of this in previous cognitive bias posts.

I guess this comes down to how similar the options are to the description, and a quantified bias of thinking the number, size or quantity of something matters more.

I hope that made sense to most of you :)

---

Thank you for your time and attention! I appreciate the knowledge reaching more people. Take care. Peace.

---

Previous Logic Comics:

• Argument from Fallacy, or the Fallacy Fallacy - Logic Comic (Pt.3)

• Appeal to Possibility - Logic Comic (Pt.2)

• Logic Comic - Anecdotal Fallacy

---

References:

• Conjunction fallacy
• Conjunction Fallacy: Concept & Example
• The Conjunction Fallacy

---

If you appreciate and value the content, please consider:

Upvoting, Sharing, and Resteeming below.

me for more content to come!

---

@krnel
2016-12-09, 5:57am