1. Learning Research & Development Center, Department of Psychology, University of Pittsburgh, Pittsburgh, PA 15260, USA
2. School of Foreign Languages, Sun Yat-sen University, Guangzhou 510275, China
3. Department of Educational Psychology, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA
4. Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA
5. Department of Linguistics, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA