This study differs from the previous studies in that it focuses on vocabulary
development process, rather than on reading or listening comprehension. While doing this, it
avoids using discrete multiple-choice tests, used extensively in the previous studies. Instead, a
vocabulary knowledge scale (VKS) developed by Wesche & Paribakht (1996) was applied as
this scale is process-oriented and compatible with the view that vocabulary acquisition is a
continuum of development.