however, basic motivation for study SLA is constant

will continue to remian the same.

the same intrest has motivated the filed.

intelletual curiosity.

six areas

first language acuqisition

difficult to solve only use first language ..

SLA can shed light on..

13岁后步行

biological capacitiy. biological constrain

deaf people..

theoretical linguistics

for example,

neurolingusitics 

in the brain.

language