Do people fluent in two languages learn a third, unrelated language more easily?

Question

The question in the title is strongly shortened. In full length it goes like this:

Do people who speak fluently two languages (which they have learned as a child) that are quite different from each other (e.g. German and Arabic) learn a third language as a foreign language which is quite different from the other two (e.g. Chinese) more easily than those who speak fluently only one language learn a second language as a foreign language?

1. Is there evidence by studies?
2. To which extent?
3. Depending on age?

References to specific studies are welcome!

The question aims at linguistic universals (à la Chomsky), not at learning techniques.

Answer 1

I hope this helps.

I'm fluent in Dhivehi (native) and English. They are very different from each other. I've tried to learn Spanish few times. On and off, but I can't seem to really go anywhere (partly because I wasn't that interested and I didn't use proper techniques). Phonetically however, the 2 languages I speak together covers almost all the sounds used in the Spanish language. I've had more issues with remembering words rather than finding the sounds too different and hard. I also didn't like how Spanish uses the accented letters such as á è ō (because that's pretty much all I have to learn in relation to letters and sounds).

But it's been about a year and a half since I started learning Japanese and I find it quite easy. Maybe because Spanish is closer to English (my second language) and Japanese is closer to my first language? Idk. That's just my personal experience :))

Also take note that Dhivehi uses most of the sounds in all of these languages. For example, the English T is considered as the equivalent of Japanese and Spanish T. But they are pronounced differently (Spanish and Japanese T is soft). An English speaker would probably pronounce it like a normal English T. In dhivehi however, both of these sounds are 2 distinct letters. So I did not have to learn any new sound.

Answer 2

This is how it could be helpful:

• Vocabulary overlap - knowing two languages obviously helps, if the third one borrowed from one of them (or both).
• Awareness of different grammatical functioning: e.g., native English speakers would struggle with Russian cases a lot more than German speakers, for whom this phenomenon is not new.
• Phonetical abilities: being able to produce greater variety of sounds, and having a better tuned ear is a great bonus. This is probably the greatest and most obvious advantage that comes from having learned several languages as a child.
• General awareness of how differently ideas can be formulated and communicated in different languages. It may seem vague, but it is quite important.

Having said all that, it is necessary to note that learning foreign language as a child and as an adult are two rather different things. The experience of regularly learning and practicing, as well as certain grammatical knowledge play important role here. I have met adults, speakers of three or more languages learned in their youth, who struggled mastering another foreign language as adults.