>>The pessimist in me likes to think this article is sponsored by the air purifier lobby.

Well that makes the two of us. For an article on a website called science, there's lots of info about the person doing research, his background and his life story than the actual numbers on what they define as "smarter"

In one part they mention the study was done in 2015 (no link to article) on 24 people where these people did 61-101% better on some test.

But then when they did the study on 100+ people the improvement was just 26.4%

Wut??

But like others have mentioned there is evidence better quality air helps with performing better on cognitive tasks. This article is just really badly written.