Interlanguage fossilization

Interlanguage fossilization is when people learning a second language keep taking rules from their native language and incorrectly applying them to the second language they are learning. This results in a language system that different from both the person's native language and second language. In 1972, Selinker showed the concept of "interlanguage fossilization".
Causes.
There are two reasons why the interlanguage fossilization happens: