Comment by idlewan

Doing a visual comparison (tab flipping between https://fonts.google.com/noto/specimen/Noto+Sans and https://fonts.google.com/specimen/Open+Sans?query=open+sans&... , aligning the sample text exactly), I could notice some differences though:

- The 'g' character was changed, they are quite different

- For the regular (400) weight, Noto Sans is slightly bolder but also more compact

But you're definitely right, most character shapes look directly inherited from one to the other.

I wonder if the weight & letter spacing change can explain the reading speed differences, or if measurement error / random jitter is actually what explains the different average speed in the study between the two.