In my day-to-day life I use three languages to communicate. I use English at work. While at home, I speak mostly in Hindi and English to communicate with my wife, and when I need to talk to my mother or sister I use Telugu, which is my native language.

Some time ago I wondered what language do I really think in ?

This is what Paul. R. Ehrlich (in his book Human Natures) says in this matter:

Steven Pinker believes that we do our thinking in a deep, rich, built-in universal language, which he calls mentalese. Mentalese presumably lacks the ambiguities introduced by the demands for efficiency of communication in the slow “channels” of speech and gesture (as compared with The much faster channels in the neurons of the brain).

My guess (I emphasize guess) is that we all use a mix of surface and deep language, depending on the topic and speed of use (for example, a warning to “watch out” may be formed entirely in subconscious thought- call it mentalese if you wish – and instantaneously translated into shout, whereas I may be thinking about this parenthetical expression entirely in English).

Though I couldn’t observe my instantaneous thoughts, I think agree with the author. As far as other comparatively long-running thoughts are concerned it seems I’m almost always thinking in the language I need to communicate them in.

So what language do you think in ?