This is a subject I am interested in as one of my Granddaughter is in University having just finished her first of 4 years learning German and Russian. Those are her majors. When she was in public school my daughter put her in French Immersion and she learned Spanish when she was in High School.
I thought the in thing was to learn Mandarin but the more I think on her choices I see the reasoning coming clearer.
So, she will have those 5 languages when she is finished there. But I do not know her future plan. She is a worker and has a stubborn streak and a go get it attitude.
I don't see her as a genius, but she is a woman with a plan.
So maybe that is what these people who speak more than one language do. See what they need to be able to do something and they learn that language. It is smart enough to figure out what tools they need.
Now that I mentioned my Granddaughter and what she is about I have to brag on her. She is paying her way through University with little bits of money here and there. When she was 16 she said to me. I'm going to go get a job when I get back there for after school. She said I can pick what I want to do because I have a pretty respectable resume for a 16 year old. She did too. Including award and completion of years of work with a team doing Rescue work. It is St John's Ambulance? I forget right now the name. But it is a great accomplishment for many people not just school age kids.
Anyway, when they got settled in Calgary for her University. First thing she went and was walking by a Dollar Store type place that was being started. She walked in and asked for a job and right then and there they hired her. After her first 6 months they offered her training in management if she wanted it and didn't go to school. She said no she was going to go to school. But she is still with them and went as far as assistant manager. I expect to hear once this is as far as she can go she moves up to another position of her choosing. I can imagine her plan may be to have a job with the business she wants when she finished University.
What her biggest strength is. Her stick-to-it-to-ness. She makes a plan and stays dead on once the choice is made. I think she gets that sticks to it part from her Dad's family. That is a good trait to breed into our genetic pool.