Individual differences such as language learning
aptitude, working memory capacity, and
motivation have been found to play a large role
in explaining second language success. However,
most of this work has been done on classroom
learners, and rarely have motivation, aptitude (of
which working memory is a part) and input been
considered in the same study. I will report on the
results of extensive interviews with English-
speaking learners of Japanese who were living in
Japan and working as missionaries for 18
months-2 years. I will consider the effect that the
length of time they have lived in the country
affects their proficiency level, and look at how
much each factor of input, motivation, and
aptitude accounts for their proficiency levels in
an oral proficiency test and an elicited imitation test.