This volume comprises of chapters that deal with language proficiency relating to a wide range of language program issues including curriculum, assessment, learners and instructors, and skill development. The chapters cover various aspects of a broad-based proficiency initiative, focusing on numerous aspects of foreign language learning, including how skills develop, how assessments can inform curriculum, how learners and instructors view proficiency and proficiency assessment, and how individual use of technology furthers language learning. The concluding chapter points the way forward for issues and questions that need to be addressed.

This Handbook, with 45 chapters written by the world's leading scholars in second language acquisition (SLA) and language testing, dives into the important interface between SLA and language testing: shared ground where researchers seek to measure second language performance to better understand how people learn their second languages. The Handbook also reviews how to best measure and evaluate the second language (L2) learners' personal characteristics, backgrounds, and learning contexts to better understand their L2 learning trajectories. Taking a transdisciplinary approach to research, the book builds upon recent theorizing and measurement principles from the fields of applied linguistics, cognitive science, psychology, psycholinguistics, psychometrics, educational measurement, and social psychology. The Handbook is divided into six key sections: (1) Assessment concepts for SLA researchers, (2) Building instruments for SLA research, (3) Measuring individual differences, (4) Measuring language development, (5) Testing specific populations, and (6) Measurement principles for SLA researchers.