[tgv]

There are possibilities that involves less biological determinism: the older, the more work done in collaboration. Or: researchers stay with their original subject, which often (remember: we're talking averages here) gradually becomes more main stream.

[ferguess_k]

We can control for the same age. But anyway it is going to be difficult to design the tests. My personal experience says, unless you really like kids, you are going to suffer a lot -- yes you are also going to have some fun, but you are definitely going to suffer a lot.