Kellerman (1989) argues that conditional sentences in these three languages are inherently complex for the human mind. There seem to be different form-function conflicts, where one form is mapped to two meanings or two forms are used for the same meaning. For example, while both parts of the sentence express the idea of conditionality, the verb is marked differently in each part. So two different forms apparently express the same function or meaning. Further, there is something particularly counter-intuitive about the if-clause verb: it carries past-tense marking when in fact the 'time' being referred to is 'now', albeit a hypothetical 'now', as in: If I had the money now .… Hence the past tense form appears to express two different functions: occurrences in the past, and occurrences in a hypothetical present, and this latter usage is of course the more 'marked'.

L2 learners instinctively seem to try to map one grammatical form to one meaning function. But in all languages there are areas of grammar where that nice, easy mapping simply does not happen, and it is in these areas that difficulties, irrespective of the L1 pattern, arise for learners.

As you have seen from the data we have reviewed in this section, difficulty for learners cannot always be judged in terms of the L1. Nevertheless, it is quite clear that similarities between L1 and target language do help learners, and nowhere more so than in the area of vocabulary, but they can sometimes be something of a double-edged sword.