The advantages are do note relate only to a linguistic aspect. They extend to the cognitive, cultural and social fields. A child who knows a foreign language, preferencially English, which is still considered the universal language, is in advantage when it comes to educational materials offered to him/her, international literature, cognitive development and further down the line, the work field.
Seeking to bring down a few of these myths, we will comence with the concept of bilingualism itself.
Bilingualism is defined by someone´s capacity to comunicate in two languages, where one can be dominant over the other.
Learning languages simultaneously does not influence childrens development at all. It has been proven through extensive studies that a bilingual or poliglote child presents the same development milestones as a monolingual child. This means that there is no delay what so ever in the development of those children, be it physical, cognitive or emotional.
As far as the advantages children have in learning a new languages, there are now no doubts. Biologically speaking, they learn easier and faster then adults. There is a chart that demonstrates these facts. See it below: