Actually, I have another way of thinking about that. It takes children about five years of 24/7 immersion (many thousands of hours) in order to attain “native” pronunciation and fluency, and even then, they talk like a five year old ;) Adult learners usually don’t have that much time to dedicate to learning <em>additional</em> languages.

As far as “easy,” it seems to me that children do a lot of crying during their first five years of life. If you tried teaching languages to adults using similar methods, your students would voice their dissatisfaction verbally (in their first language), and look for another teacher. Little children have no such options.

First of all, Tugba, welcome to italki, and thanks for posing such an interesting question for discussion.

In your example, a child learning English always hears adults putting the adjective before the noun, so he or she unconsciously assimilates the rule. Adults can make faster progress if you point the rule out to them. This is true of every skill (as opposed to academic knowledge), not just language acquisition. The child doesn’t consciously know what a noun or adjective is, but he handles them correctly. An adult can learn to do the same thing in a second language, but only if he’s willing to accept that he is going to have to learn a new skill. If you’ve always played American football, and then you start playing soccer (international football), you’re going to have to learn a new game. It’s no harder than learning your first game, but the rules are different in soccer, for example, you can’t touch the ball with your hands or deliberately knock your opponents to the ground and get on top of them.

I guess there is a most significant point to distinguish the learning of adults and children:

# Most of the adults do not have analogus environment as children have

--> Children can have 24/7 time to immerse themself passively/actively to a target language and they do have the most various scenarios to learn a new language without interference from their primary language as an adult. However, that does not refer to children learn a language very easily without a tough course. Look at children who wish to become a sophisticated speaker and a reading. Most of the children have to consume 6-8 years to master a language which is not thought to be a short time. 

Thank you Phil, these are valuable ideas. I think so. It is really difficult to replicate native language acquisition in terms of all of its features, but maybe I thought I can provide some elements of native environment embedded in the overall design of lessons. Moreover while using this aspect of language learning, there would be more advantages which native children have to develop along with language. First one is that second language learners have already built-up world knowledge, and second one is that they have already developed cognitive skills. But I am still searching for some eclectic methods which will not frustrate the language learners as you say :)

@Tugba: I haven't studied the question exhaustively, but I am convinced that Chomsky's concept of Universal Grammar is at least largely correct. I have yet to read of any other theory that accounts for the similarities in a more connvincing manner. Do you have an opinion for or against it?