Learners' output proceeds along predictable paths

Second language learners’ output follows predictable developmental sequences.

For example, regardless of first language background, learners acquire English negation through the following stages (reproduced from vanpatten2015introduction: 10):

1. no + phrase, e.g. No want that,
2. subject + no + phrase, e.g. He no want that.
3. don’t, can’t, not may alternate with no, e.g. He can’t/don’t/not want that.
4. Negation is attached to modal verbs: He can’t do that.
5. Negation is attached to auxiliaries: He doesn’t want that.

There are also orders of acquistion for certain grammatical structures. For example, English verbal affixes are acquired in the following order:

1. the -ing suffix
2. the regular past tense suffix -ed
3. irregular past tenses, such as went
4. the 3rd person singular present tense suffix -s

Learners often exhibit U-shaped learning, where they start out doing something correctly, then incorrectly, and finally correctly once again.

References

• vanpatten2015introduction: 10