Grammar vs Vocabulary

When learning a language, which is better? Teaching a ton of vocabulary first and working on the grammar later? Or working through rules of sentence structure at the beginning with the vocabulary?

A pair of scientists in Leipzig is taking a medical approach to this question and at the same time helping out their fellow refugees in town. They have started with 90 students who never studied German before and are teaching them the language. They scan the brain with an MRI before the semester starts, in the middle and again at the end to see what effects learning a new language actually has on the brain.

http://www.npr.org/sections/health-shots/2017/01/03/508033549/learning-german-in-the-name-of-science-and-cross-cultural-collaboration?utm_source=npr_newsletter&utm_medium=email&utm_content=20170105&utm_campaign=npr_email_a_friend&utm_term=storyshare