That's what she said: Guiding Patients Away from Anecdotal "Proof"

“My grandmother smoked all her life and lived to 90, so smoking can’t be that bad.”

I’ve seen this kind of comment on every post about healthy habits or health recommendations.

Let’s see how to address this question by starting with a very simple and accessible story:

Imagine we have a huge bag with 10.000 colorful marbles. Most of the blue marbles crack or get scratched when dropped, but 1.000 blue marbles stay perfect! Just because you found one perfect blue marble, doesn't mean all blue marbles are safe from getting scratched.

It's the same with your grandmother! She was like that super strong marble - very special and rare.

Most people who smoke are more likely to get sick, just like most blue marbles get scratches. This doesn't mean everyone who smokes will get very sick, just that they have a bigger chance of getting sick - like how dropping a marble doesn't mean it will break for sure, but it has a bigger chance of getting scratched or cracked.

So even though your grandmother lived a long time while smoking, she was like that rare, super strong marble. Just because something isn't healthy doesn't mean it will make you sick - it just means you have a better chance of staying healthy if you avoid it, just like you have a better chance of protecting your marble if you don't drop it!

Think about this: how many marbles do you know? How many marbles exist?

To have in mind

The purpose of the story is to show a simple way of explaining the anecdote fallacy, you can adapt it as you want.

Next are some points that guided us to craft this story:

• Pick a common object: Most people is familiar with marbles, have seen it, or manipulated it.

• Select a feasible scenario: Marbles dropping while some of them break and scratch is a real-life scenario.

• Use quantity: At first, we used “thousands” of marbles and “most of them get cracked” but this was too broad, and undefined. Using quantities allowed us to lead the interpretation and narrow it to put our point in the desired perspective.

• Mix the stories: After establishing the opening story, put in parallel both of them, clearly pointing out which part of the story relates to the other. Like we did on “It's the same with your grandmother! She was like that super strong marble”

• Invite to introspection: At this point, you will have already sown doubt in the reader. Now just provide the last gentle push and leave a question that encourages to reflect on all you said.

I hope you found this helpful, and please use the comment section to share your opinion, doubts or concerns about this.