[eah13]

I believe they're roughly synonymous, yes. The processes of aging and aculturation both involve an ossification of our ideas and concepts that make learning new ones comparatively difficult. Vinod Khosla has talked extensively about how he has to fight these processes in himself to bring a 'beginners mind' to bear on new startup ideas. The median effort required to do this is lower in younger people.

By the way, older people who share the characteristics of being only lightly acculturated (i.e. eccentric) share the relevant characteristics with children and may be able to learn things like languages with childlike speed. Hence, I believe, PG's observation that startup founders of any age tend to be weird, quirky, or poorly socialized in various ways.