I'm not sure those people are hyperpolyglot (whatever that exactly means). They usually have extreme skills in two languages, one being their native language.
However, a task like simultaneous translation is tough. It requires a different way of focusing, and has other demands on working memory. There is some evidence that it leads to "functional" changes in the brain. That could be a factor. OTOH, since the effect is bound to a small group living in a few places, it could just as well be a life-style effect.
However, a task like simultaneous translation is tough. It requires a different way of focusing, and has other demands on working memory. There is some evidence that it leads to "functional" changes in the brain. That could be a factor. OTOH, since the effect is bound to a small group living in a few places, it could just as well be a life-style effect.