Often, it's claimed that in a group, you have people to practice verbal exercises with, as well as potential proofreaders and error-checkers to verify the grammar and spelling of your work. However, I've found nothing to the like on the Internet.
Are there any studies addressing the fact that it is often claimed that learning the same new language with two or three friends or family members can help you learn the language faster? I'm fine with referencing your own personal experience, but scientific references are preferred. (All members of the group are learning the same language, and all have the same native language).