Both privately and professionally I have been living in five languages (English, Hebrew, Japanese, Yiddish and Esperanto) for quite some time, though I use them in different degrees of frequency, depending on the modes of usage (listening, speaking, reading and writing). Recently I prepared statistics of my research output, both in speech and in writing, using my list of presentations and list of publications, and have confirmed a few things I always felt. One is that my research output is characterized by polyglossia, and another is that the constellation of these five languages in this personal polyglossia of mine has changed over the years.
"Polyglossia" is a sociolinguistic term referring to the phenomenon of using multiple languages complementarily for different functions. Generally speaking, polyglossia presupposes multilinguialism, but not vice versa; someone can use multiple languages equally with no functional differentiation, though such a polyglot must be quite rare.
Among the five languages mentioned above I use English, Hebrew and Japanese far more frequently than Yiddish and Esperanto in my research output, but the use of the first three languages is in complementary distribution. In oral presentations I have been using Hebrew most frequently, not only after I immigrated to Israel about seven years ago but also, to my surprise, even before that, but I have published far less in Hebrew than in English and Japanese. In other words, the general pattern is to give talks first in Hebrew, then transform them to articles and publish them in English. This also matches my overall proficiency in these languages, that is, I speak Hebrew better, but I read and write English better. As for Japanese, after immigrating to Israel I have decided to use it only for the general public in Japan, as few serious researchers in my areas of interest understand it.
The dominance of Hebrew in my oral presentations will probably remain stable as I have more chances to participate in conferences in Israel than abroad, but the share of English may increase in the future as I would like to participate in more conferences that are not specific to Hebrew and Jewish studies but are on aspects of general linguistics and are held abroad. As for articles, I have been making a conscious effort of publishing more and more of them in English for reasons that must be clear to everyone. Here, too, I have decided to restrict the use of Japanese to articles for the general public in Japan. But in Hebrew, Yiddish and Esperanto I hope to publish more in absolute terms, if not in relative terms.