It happens when you least expect it. You could be strolling along the road, riding in a car, relaxing on a park bench, eating lunch in a local eatery, or minding your own business, and somebody says Hello in whichever language seems to be prevalent. You respond without thinking, in the wrong language.
The funny thing I’ve noticed is that I will sometimes answer in French when I don’t know the answer in Japanese. I must be trying to make up for my lack of Japanese skills by showing off my French! Or my lack thereof. Living in Japan has given me a new perspective on language acquisition; it really is easier to learn when you are immersed. I’ve been in Japan for just over a month and more progress has been made with Japanese than in the same amount of study with French.
I’ve discovered that learning a third language has increased my proficiency in my second language and my first one. One language makes the others better and so on and so on. Considering new vocabulary in more than one language helps with acquisition and learning new vocabulary in one language instills a curiosity about what it could be in the other languages. There are some words and phrases that deny direct translation but it’s all exploration. Try to make as many connections as possible when learning new vocabulary, repeating the words from each language consecutively helps. Take left and right, for example. Look in each direction as you say them. Left, Gauche, Hidari, Right, Droit, Migi. Drill it in with muscle memory while you say it or think it to increase your chances of remembering new vocabulary.
Memorization is very difficult for me; my memory is not a steel trap, as they say, (I visualize my memory as a colander or strainer with oversize holes) and hearing something gives me only a conceptual representation of what I’ve seen or heard. The word flies away into the sunset to wait for me to pick up tomorrow, where it turns to dust in my hands. But each time less dust falls through my hands and suddenly I find the new vocabulary a part of my canon.
So get out there and think language, do language, and above all, experience life!