If you dig in you’ll find that for simple cognitive tasks they found no effect.

Then they analyzed only complex cognitive tasks. But fewer studies included complex cognitive tasks, and they used different methods of adjusting CO2 exposure (ventilation vs adding pure CO2)

Then you’ll note that of those studies they found that:

“The effects of pure CO2 on complex cognitive task performance decreased with increased CO2 concentrations”.

Between 1000-1500, and 1500-3000ppm they found a decrease in complex cognitive tasks performance, but at a higher exposure of 3000-5000ppm they found no effect.

This makes no sense until you read

“the complex cognitive task results under pure additional CO2 concentrations of 1000–1500 ppm and 1500–3000 ppm showed publication bias.”

Handful of studies (many with sketchy methodology—reducing ventilation, which brings with it many more variables than just increased CO2), publication bias, and a negative dose dependent response.

Also that Satish et al. study (the author is the one I was referring to in my last post—they also have several other studies on the subject) shows an enormous effect IIRC, which would skew the aggregate effects in the meta study.

The effect sizes in that study were the ones I was referencing when I said that such effects would be obvious.