I was told by one of my teachers back in my undergraduate days about twenty years ago that for me to master Japanese it would take me 700 hours of class time.
The number now seems to be 2,200 hours.
Japanese is a language notoriously difficult to learn for native English speakers because of their linguistic differences.
To start with, Japanese has three writing scripts – hiragana, katakana and kanji. Hiragana and katakana are syllabic scripts with, in general, one unit representing one fixed sound where most units are consonant-vowel pairs. Kanji are logograms with each unit representing a word (meaning) but not its pronunciation. Most people know kanji as Chinese characters.
English, in contrast, is based on an alphabetic script where each unit is a representation of a sound be it consonant or vowel. Each letter may represent more than one sound (examples: ‘c’, ‘g’, ‘a’, ‘e’, ‘i’, ‘o’ and ‘u’) and sometimes conbinations represent a single sound (examples: ‘ch’, ‘sh’, and ‘th’).
So how difficult would it be for a native Japanese to learn English? Because of the simplicity of the alphabetic script one would think that it would be much easier. But I have simplified the understanding here. Firstly, a language is not just about writing. It is about speaking, reading and listening as well.
The Japanese have a lot of difficulty in producing and understanding (receiving) English speech and writing. It would be easy to put it down to L1 interference. But the problem is not just this. Interference may be part of the problem but I think also the understanding of the nature of language is a greater factor.
Language is seen, at the beginning of the L2 learning process, as a kind of one-to-one correlation between words and meaning. This is most evident when learners believe that meaning can be conveyed by simply stringing words together like stacking building blocks. But to convey meaning is more complex than this. How you say something is just as important as what you say. The words have to be right, of course, but the delivery, too, is just as crucial, if not more.
Just think ‘robotic speech’.
Still, I need to answer the question raised in the post title.
One number I came across about how long it would take a Japanese to master English was 10,000 hours. But honestly, if you think 10,000 hours then it will take 10,000 hours. Wish fulfillment is Freudian. It also has nothing to do with the writing script of the target language or the lack of certain sounds in the native language, and everything to do with attitude towards language and culture.
The real irony is that the answer the Japanese are looking for can be found within its culture:
Matajuro Yagyu was the son of a famous swordsman. His father, believing that his son’s work was too mediocre to anticipate mastership, disowned him.
So Matajuro went to Mount Futara and there found the famous swordsman Banzo. But Banzo confirmed the father’s judgment. “You wish to learn swordsmanship under my guidance?” asked Banzo. “You cannot fulfill the requirements.”
“But if I work hard, how many years will it take to become a master?” persisted the youth.
“The rest of your life,” replied Banzo.
“I cannot wait that long,” explained Matajuro. “I am willing to pass through any hardship if only you will teach me. If I become your devoted servant, how long might it be?”
“Oh, maybe ten years,” Banzo relented.
“My father is getting old, and soon I must take care of him,” continued Matajuro. “If I work far more intensively, how long would it take me?”
“Oh, maybe thirty years,” said Banzo.
“Why is that?” asked Matajuro. “First you say ten and now thirty years. I will undergo any hardship to master this art in the shortest time!”
“Well,” said Banzo, “in that case you will have to remain with me for seventy years. A man in such a hurry as you are to get results seldom learns quickly.”
“Very well,” declared the youth, understanding at last that he was being rebuked for impatience, “I agree.”
Matajuro was told never to speak of fencing and never to touch a sword. He cooked for his master, washed the dishes, made his bed, cleaned the yard, cared for the garden, all without a word of swordmanship.
Three years passed. Still Matajuro labored on. Thinking of his future, he was sad. He had not even begun to learn the art to which he had devoted his life.
But one day Banzo crept up behind him and gave him a terrific blow with a wooden sword.
The following day, when Matajuro was cooking rice, Banzo again sprang upon him unexpectedly.
After that, day and night, Matajuro had to defend himself from unexpected thrusts. Not a moment passed in any day that he did not have to think of the taste of Banzo’s sword.
He learned so rapidly he brought smiles to the face of his master. Matajuro became the greatest swordsman in the land.
from Zen Flesh, Zen Bones
I don’t really think this question is a question about time, but rather it is a question about how teachers can guide students to learn how to master another language regardless of time. As teachers we often forget it is more than just about teaching English but also about the nature of language and, as students, how to approach it with the right frame of mind.