[I actually wrote this about 6 months ago and I'm not sure why I didn't publish it. I've read it over and it looks finished to me...]
It's always seemed weird to me that some people claim that L2 errors are not related to the form of the learner's L1. Surely it's common sense? For instance, a speaker of Chinese, or Polish, or any other language with no articles is going to have a problem learning when to use "a", when to use "the" and when not to use an article at all in English, right?
But of course, common sense is only common sense until it's proven wrong. It was once common sense that the sun went round the Earth and that there was such a thing as "races" of people -- scientific study has since shown us otherwise.
So language must be open to scientific study, and teachers must be open to the results of study. And there are plenty of studies that purport to disprove the idea of cross-linguistic interference.
For example, I'm currently skimming through bits of the book Understanding Second Language Acquisition by Lourdes Ortega. There's a chapter on "cross-linguistic influences" (they reject the term "interference", because they reckon it puts too much blame on the L1) and they open by looking at a couple of studies that show that the similarities and differences between languages have less influence than might be expected. The first of these is to do with the placement of negatives in Swedish, where they find that learners on the whole tend to incorrectly place negatives before the verb, even if their own language also places negatives after the verb. [Hyltenstam, K., 1977. Implicational patterns in interlanguage syntax variation. Language learning, 27(2), pp.383-410.]
What questions does this raise? First I would say that negation is an undeniable universal of language, so here we're talking about a linguistic concept that is already known to the learner, and the only variable under examination is word placement -- syntax. There is no examination of usage -- for example, what happens with complex clauses? In English we most commonly say "I don't think so", but some languages are more likely to say "I think not", which now sounds quite old-fashioned. It's far more likely that a native English speaker would say "I don't think he's coming" than "I think he's not coming", but "creo que no viene" is perfectly normal in Spanish. It's readily apparent that this sort of transference occurs at the phrasal level, and this is the sort of thing that is often never taught and simply left to the student to work out. It is also readily observable that learners make errors handling polysemy (multiple meanings of a single word) -- again, looking at Spanish "esperar" is to wait, to hope and to expect, and it doesn't take long in the company of Spanish learners of English to hear someone pick the wrong one of the three.
I haven't had a chance to read the original paper yet (I'm not familiar with my new university's online search and I'm feeling too impatient today to start hunting) so for the moment I'm just thinking about what I'll be looking for when I get round to reading it (which might not be for a while!). First up, is there anything that goes deeper than simple word placement? Secondly, as a tangent to the point about cross-language transfer, and continuing the thread on slots, does something change when it's a multi-part structure, with the two sections separated by other language content?
Besides, is negatives even a fair example? My gut reaction is that in every language that I've come across a sort of "Tarzan speak", the stereotypical form is for pre-negation ("me no hurt pretty pretty" and the like).
The second paper cited discusses object pronoun placement in French-speaking learners of English and English-speaking learners of French. [Zobl, H., 1980. The formal and developmental selectivity of LI influence on L2 acquisition. Language learning, 30(1), pp.43-57.]
Again, I've not read the paper yet, but the summary in the book baffles me a bit, because it seems somewhat obvious. We have the example of the pair "je les vois"/"I see them" and it is observed that English speakers often erroneously say "*je vois les", but French speakers don't tend to say "I them see". This is not a symmetrical error, but then, this is not a symmetrical pattern. As I see it, the difficulty for the English speaker isn't simply one of the absolute position of the pronoun, but the fact that pronouns appear in a different place from explicit noun phrases as object -- je les vois vs je vois des hommes. The English speaker learning French has the difficulty that he sees pronoun noun phrases and explicit noun phrases as subcategories of a single thing that share a position, and in order to learn French accurate must learn a fundamentally new distinction between weak pronouns and other noun phrases. The French learner of English, conversely, doesn't necessarily need to learn the English speaker's categorisation, and can maintain the French distinction and notion of two slots, and can then simply focus on the syntax, learning two different positions that happen to be the same. It feels to me that focusing on the superficial differences here has failed to account for the real underlying difference.
Another question this leaves in my head is about my own observations from dealing with Romance speakers. I recall hearing a lot of them dropping weak pronouns altogether, and my first reaction is that the article focuses on the lack of examples of "*I them see" as proof that there's not a problem, but doesn't comment on the presence or absence of examples of pronounless renderings (i.e. "I see", with no them). My observation from my own pupils was that several of them had learned not to place the pronoun before the verb, but if the verb in Spanish would be the last word of a sentence, they'd just stop without including the pronoun at all. I'm now left second-guessing my own recollection here, though, as recently I only recall hearing this error with Spanish people saying "I like" for "me gusta", and of course there's no explicit "it" in the Spanish, so that's a different issue (but still cross-linguistic).
This is an issue that intrigues me, and I hope to revisit it during the year when I'm working on cross-linguistic issues as part of my masters. For now, though, I just wanted to get my thoughts jotted down for future reference.