Psycholinguistic Conditions for L2 Vocabulary Learning

I read chapter 2 and 3 of Nation(2001) yesterday and today. 90pages long are all about vocabulary obviously. I could not concentrate on just vocabulary! But it turns out the vocabulary contains various topics.

Psycholinguistic Conditions where L2 vocabulary learning is likely to occur is one of the topics. These are noticing, retrieval, and generative/creative use. Psycholinguists, or Psychology is beyond my understanding, because it is assured by empirical testing, and the conceptions cannot be out of metaphor. It is inevitable, because we cannot see directly how our brains go on! Metaphor and testing can explain the phenomena, but it cannot account for everything i think. How do you think of it?

But, it does not mean these disciplines are meaningless, rather useful and helpful for teachers to gives clues for better language teaching.

Nation(2001) refers to effectiveness of L1 translation for the target L2 vocabulary. It is a bit surprising for me because i have learned language are better learned in contexts and from exposure than translation in many classes at this grad school. Dr. Nation argues teachability hypothesis may not be applied to vocabulary learning.
Moreover, he discuss, when L1 translation for the L2 vocabulary is restricted within one strand of vocabulary teaching design (consisting of Meaning focus input, Language focused learning, Meaning focused output, and Frequency development. it means it is restricted in Language focused learning), and when the vocabularies are high-frequency or important words in running texts, L1 translation is helpful for learners. That is really interesting point!