AUTHOR=De Santo Aniello TITLE=Commentary: Developmental Constraints on Learning Artificial Grammars with Fixed, Flexible, and Free Word Order JOURNAL=Frontiers in Psychology VOLUME=9 YEAR=2018 URL=https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2018.00276 DOI=10.3389/fpsyg.2018.00276 ISSN=1664-1078