cont....

Language acquisition is one of the central topics in cognitive science. Every theory of cognition has tried to explain it; probably no other topic has aroused such controversy. Possessing a language is the quintessentially human trait: all normal humans speak, no nonhuman animal does. Language is the main vehicle by which we know about other people's thoughts, and the two must be intimately related. Every time we speak we are revealing something about language, so the facts of language structure are easy to come by; these data hint at a system of extraordinary complexity. Nonetheless, learning a first language is something every child does successfully, in a matter of a few years and without the need for formal lessons. With language so close to the core of what it means to be human, it is not surprising that children's acquisition of language has received so much attention. Anyone with strong views about the human mind would like to show that children's first few steps are steps in the right direction.
Language acquisition is not only inherently interesting;

How do we explain children's course of language acquisition , most importantly, their inevitable and early mastery? Several kinds of mechanisms are at work. As we saw in section , the brain changes after birth, and these maturational changes may govern the onset, rate, and adult decline of language acquisition capacity. General changes in the child's information processing abilities (attention, memory, short-term buffers for acoustic input and articulatory output) could leave their mark as well. In the next chapter, I show how a memory retrieval limitation , children are less reliable at recalling that broke is the past tense of break can account for a conspicuous and universal error pattern, overregularizations like breaked .

Many other small effects have been documented where changes in information processing abilities affect language development. For example, children selectively pick up information at the ends of words , presumably because these are the parts of strings that are best retained in short term memory. Similarly, the progressively widening bottleneck for early word combinations presumably reflects a general increase in motor planning capacity. Conceptual development , too, might affect language development: if a child has not yet mastered a difficult semantic distinction, such as the complex temporal relations involved in John will have gone, he or she may be unable to master the syntax of the construction dedicated to expressing it.
The complexity of a grammatical form has a demonstrable role in development: simpler rules and forms appear in speech before more complex ones, all other things being equal. 
 
Children often use each marker with the correct case, never using a nominative marker for accusative nouns or vice-versa, but don't properly use the masculine and feminine variants with masculine and feminine nouns.