The same advanced search dialog has a language setting, that is also not reflected in the search string. The search engine gets it via a URL parameter. For example, if we set the language to English, the added URL piece will be &lr=lang_en.
Suppose we are looking for English-speaking people in a non-English speaking region. If we X-Ray LinkedIn (or another social site) for member profiles, using the language restriction, in the results, we will see pages that we can informally describe as having “lots” of English. Members behind those profiles are likely to speak the language.
Here is an example search in the Netherland-based LinkedIn, narrowed to the English language:
Without any keywords, we’ll see some Netherlands-based profiles that have English content, such as a summary or a description of job responsibilities. If we add keywords, we’ll also start seeing profile URLs ending in /en – those are “secondary,” English-language, profiles. Either way, we are encountering people who use English to describe their professional background and are likely to speak the language – which is what we need!
Try these searches (add keywords to make them interesting) and observe how the language setting works: