Explaining the “Natural Order of L2 Morpheme Acquisition” in English: A Meta-analysis of Multiple Determinants Jennifer M. Goldschneider and Robert M. DeKeyser University of Pittsburgh Some researchers have posited a “natural” order of acquisition of English grammatical morphemes common to all learners of English as a second language, but no single cause has been shown for this phenomenon. This meta-analysis investigated whether a combination of five determinants (perceptual salience, semantic complexity, morphophonological regularity,syntactic category,and fre- quency) accounts for a large part of the total variance found in acquisition order. Oral production data from 12 studies over almost 25 years, together involving 924 subjects, were pooled. Multiple regression analysis showed that a very large portion of the total variance in acquisition order is explained by the combination of the five determinants. We suggest research on other potential contributing fac- tors and discuss the need for similar research in other languages. Language Learning 51:1, March 2001, pp. 1–50 1 Robert M. DeKeyser and Jennifer M. Goldschneider, Department of Linguistics. The authors gratefully acknowledge the advice and feedback from Alan Juffs, Margaret MacEachern, Sarah Thomason, Nick Ellis, and several anonymous reviewers, and the statistical help and advice from Elaine Rubin- stein. Correspondence concerning this article may be sent to Robert DeKeyser, Department of Linguistics, University of Pittsburgh, Pittsburgh, PA 15260. Internet: RDK1@pitt.edu