>Twin studies of adult individuals have found a heritability of IQ between 57% and 73% with the most recent studies showing heritability for IQ as high as 80% and 86%.
The reason that icon sets are similar is probably because they are quite ingrained into our memory. The save icon, although younger people have no idea what it's supposed to represent, is evident to them to be the save function. And since icons are generally meant to guide the user, then you opt to use something they already know. After all they do not have much agency compared to the main content of an app or site.
>Twin studies of adult individuals have found a heritability of IQ between 57% and 73% with the most recent studies showing heritability for IQ as high as 80% and 86%.
https://en.wikipedia.org/wiki/Heritability_of_IQ