being well-read implies being exposed to different things [...] But those who are exposed to a wide variety of things are highly correlated with those who wish to take risks to be exposed to new things
I don't follow this reasoning. Being well-read implies being exposed to a lot of different books, not a lot of different activities. In my experience, people that read a lot are not people who take risks to be exposed to new things, precisely because they have rather intellectual hobbies and they have less free time due to reading a lot.
Good point. And I don't know how the vocabulary test was made. I think the monotonicity can be explained by, in general, people who read marginally more are marginally exposed to more things (even after to discounting for the important fact that there is less free time and they're more intellectual, etc.). But it's a very good point.
It seems like there are a lot of different factors.
I don't follow this reasoning. Being well-read implies being exposed to a lot of different books, not a lot of different activities. In my experience, people that read a lot are not people who take risks to be exposed to new things, precisely because they have rather intellectual hobbies and they have less free time due to reading a lot.