Code switching
Communication at the level of ordinary speakers depends on the intensions they have. Whenever it happens, people express either positive or negative emotions. Even if being a layman in one of the languages, speakers may find a way of expressing own intensions by means of gestures, mimics, etc.
There is a certain phenomenon that is admitted by most of linguists called code switching. It is the process of swallowing between languages. It happens when a person substitutes the phrases of his own language with phrases from a co-existing language.
This code-switching is very often present in conversations. Everything depends on the person's attitude and his desire to show sympathy/antipathy towards another language. Bilingual interaction may take place between speakers even without code-switching. In Scandinavia, for example, it is common to use both Swedish and Norwegian in the bordering territories not differentiating them in a great way.
The same thing was observed in Czechoslovakia when Czechs and Slovaks understood both languages almost completely.
If people want to express sympathy, they look for common features in conduct. Whereas they wish to express antipathy to each other, they look for every possibility to express hostility.
