Contrastive analysis assumed learners' errors came mainly from:

1. Contrastive analysis was the principal early theory of second-language development. 2. It assumed errors were caused by differences between the learner's first language and the second language. 3. It therefore expected a comparison of the two languages to predict learners' difficulties. 4. Later error analysis found that many learner behaviours could not be explained by transfer alone. 5. Random lapses, low intelligence and motivation were not its explanation. 6. So the answer is differences between L1 and L2. **Why the other options fail:** - Random lapses of memory were not its explanation, since it predicted errors from language differences. - Low intelligence was not its explanation either. - Weak motivation was also not its claim; it blamed the difference between the two languages. _Source: Wikipedia, "Interlanguage", section "Background" (revision 1370333900)_