On Qualitative Differences between Types of Language Acquisition / Jürgen Meisel

On Qualitative Differences between Types of Language Acquisition / Jürgen Meisel, in colloque "Bilingualism vs. monolingualism: a new perspective on limitations to L2 acquisition" organisé par le laboratoire Octogone-Lordat (Université Toulouse 2) sous la responsabilité de Barbara Köpke (UT2J), Holger Hopp (Technische Universität Braunschweig), Tanja Kupisch (Universität Konstanz), Université Toulouse Jean Jaurès, 19-20 juin 2017.

The thematic focus of this workshop lies in the questionwhether there exist qualitative differences between L2 and L1 acquisition. Thishas been a core issue in acquisition studies ever since L2 researchers turnedtheir attention to mental activities of learners, 50 years ago. Theepistemological rationale motivating this research agenda is the expectation ofgaining insights into the nature of the human language faculty. Comparisons ofacquisition types, e.g. monolingual (L1) and bilingual (2L1) first and child(cL2) and adult (L2) second language acquisition, can reveal parallels anddifferences in their speech that should enable us to identify factors causingsuch differences to appear. In other words, we might discover the possibilitiesand limits of the language making capacity.
However, few of the insights achieved by past research onsimultaneous and successive bilingualism are commonly valued as such, althoughthe claim that acquisition types differ in numerous ways is not contested. Yetthe consensus ends here. What counts as ‘qualitative’ difference is acontroversial issue, not to mention the problem of determining causal factors.I therefore propose to state explicitly the criteria defining qualitativedifferences and discuss them in some detail, for in distinguishing acquisitiontypes we can only refer to these. 
It would be naïve and probably not even desirable to aim ata broad consensus on all issues involved. But if we succeed in identifyingempirical findings that do constitute differences distinguishing acquisitiontypes, a more solidly fact-based discussion will be feasible. As a first step,I argue that not every example of variable use qualifies as a criterion todistinguish acquisition types; past research has not duly consideredvariability of use within and across individuals and learner types, includingL1. Secondly, I emphasize an apparently self-evident point that tends to beoverlooked: quantitative differences are not qualitative ones. Thirdly, it mustbe stated explicitly whether observed differences reflect different kinds oflinguistic knowledge, acquisition principles, or processing mechanisms.Fourthly, contrasting ‘languages’ as a whole does not yield useful results; weneed to know whether attested differences emerge in the lexicon or in thevarious components of grammar. Finally, I examine what the identified qualitativedifferences reveal about the relevance of possible causal factors.