I joined NATS in 1986 on 62 Course.
After starting our training, we were sent to do the RAF selection tests.
At our graduation we were shown how we had done in these tests.
One of the highest marks was achieved by the first person to fail a course.
I would not have been selected
A statistical analysis of all the factors only showed ONE strong correlation.
The YOUNGER you start a course the better chance you have of passing.
NATS have spent millions trying to identify
"IT" but like all ANSPs have seemingly yet to succeed.
I have been lucky, managed to validate all of my ratings and still enjoying my job to this day.