Confirmation bias

January 9, 2017

(This article was originally published at Statistical Modeling, Causal Inference, and Social Science, and syndicated at StatsBlogs.)

Shravan Vasishth is unimpressed by this evidence that was given to support the claim that being bilingual postpones symptoms of dementia:

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My reaction: Seems like there could be some selection issues, no?

Shravan: Also, low sample size, and confirming what she already believes. I would be more impressed if she found evidence against the bilingual advantage.

Me: Hmmm, that last bit is tricky, as there’s also a motivation for people to find surprising, stunning results.

Shravan: Yes, but you will never find that this surprising, stunning result is something that goes against the author’s own previously published work. It always goes against someone *else*’s. I find this issue to be the most surprising and worrying of all, even more than p-hacking, that we only ever find evidence consistent with our beliefs and theories, never against.

Indeed, Shravan’s example confirms what I already thought about scientists.

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