Jon Clenton is Associate Professor at Hiroshima University, Japan. His main research interests include the assessment of vocabulary knowledge, L2 vocabulary development in terms of bilingual models, second language acquisition, word association studies, lexical processing, and L2 measurement tools. He has examined several vocabulary measurement tools, with focus on attempts to isolate the construct of productive vocabulary knowledge. Paul Booth is Senior Lecturer at Kingston University, London, and teaches both undergraduate and postgraduate courses. His research interests include second language vocabulary, especially individual differences, lexical diversity, and frequency. He has also researched situated learning and language teacher development.