At my peak in mid-2014, I was part of the way through my second Japanese textbook, "Japanese for Busy People II". Since then, I have tried maintaining the level of language I had, and picking up bits of vocabulary, but with no intention of learning new grammar or kanji.

I've just started learning a third language, Mongolian. Is maintaining my second language (as opposed to forgetting about it) likely to be detrimental on learning a third language?

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    Closely related (but about the effect of L2 on L1): languagelearning.stackexchange.com/q/291/13
    – Flimzy
    Commented Apr 19, 2016 at 20:08
  • Mongolian and Japanese are said to be similar. So, for those aspects that are similar, the two languages may strengthen each other. Commented Apr 15, 2019 at 3:17

1 Answer 1


Well, there is an entire study on this!

Salaberry concluded that the participants with advanced knowledge of their L2 outperformed the participants with low L2 proficiency in the acquisition of past tense aspectual markers in the L3.

So, keeping your L2 can help with your verbs in the L3. The more of the L2 you know the better.

She also noted that the learners with a higher L2 proficiency scored higher on all of the presented tasks, yet there were still other factors to consider such as amount of L2 input received and the activation of L2 during the study itself.

Still, those more proficient in L2 are more likely to do better on all the tasks given, give or take a few due to other factors involved. This quote is from another study in the actual study.

They concluded that advanced knowledge of L2 English, (over advanced knowledge of L3 Dutch) was the best predictor of the participants’ accuracy of learning the new L3 words

Surprisingly, the amount of knowledge of L2 can better predict your learning accuracy of L3 words instead of your knowledge of L3 itself! This quote was found in the study from another study.

The results only further proved that being more advanced in your L2 can help with your L3 tremendously:

The high L2 proficiency group produced target-like pronunciations 94% of the time, and an L2- like alveolar trill the remaining 6% of the time. There were no instances of L1 like pronunciations for this group

A 94 percent accuracy was shown when the group with high L2 proficiency was told to pronunciate 16 different target words from the L3. Thus, for a better L3, keep your L2 and make sure you are very proficient in it.

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    Your first quote doesn't support your conclusion. The quote indicates that having a high knowledge of an L2 helps with an L3--it says nothing of sustaining an L2.
    – Flimzy
    Commented Apr 19, 2016 at 19:36
  • @Flimzy Can you have an excellent knowledge of something you don't know? Commented Apr 19, 2016 at 19:38
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    You seem to be missing my point, and the point of the question. The question is whether maintaining an L2 is detrimental to learning an L3. Clearly the question comes from a place of knowing an L2. And your quote discusses that an L3 can build upon knowledge of an L2. But your quote does not address the issue of maintaining an L2.
    – Flimzy
    Commented Apr 19, 2016 at 19:42
  • As a whole, your answer addresses the question of "Can an L2 help in learning an L3?" But that's not what was asked.
    – Flimzy
    Commented Apr 19, 2016 at 19:43
  • I haven't read the study, but could it be confusing correlation with causation?
    – Golden Cuy
    Commented Apr 19, 2016 at 20:51

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