Can practicing vocabulary from a second language to the same second language instead of from a second language to your first language be more effective?
Example: Suppose I know German and I’m learning English.
Instead of learning that brain means the same as Gehirn, I would learn that brain means the same as the organ that is used for thinking and that is in the head.
I would imagine that when you are already more experienced with the second language, it could be really effective since you are only doing L2. On the other hand, you need to read much more. However, a dictionary from one language to the same language often explains things better than a dictionary from one language to an other language.
If I want to focus on learning new vocabulary, is second language to second language or second language to first language better? Has any research been done?