Language and thinking - what's the connection?

As I drove to work this morning, I decided to return to my old habit of driving in silence to think and talk to myself. I have been listening to the radio too much lately anyway. 

And so I did just that - think and talk to myself as I commute. 

Midway through, I thought I should do it in Mandarin, since I need to get used to speaking in Mandarin anyway but I immediately got stuck. 

I couldn't do it. I couldn't think at all. I do not have enough knowledge or a fluency of the language to facilitate my thinking. This brought me to conclude that language and thinking is very, very closely connected. 

John W. Santrock in his book on psychology said that, "The relationship between language and thinking is an important question in psychology. Most agree that language (that is, words), plays an important role in memory and thinking...language determines the way we think."

Is that so?

Would you be able to think more effectively and deeply if you improve your command of your language? Is it true that if any one word does not exist for you, you will have no knowledge or understanding of that thing? And even if you have a picture of it, would you be able to articulate it well enough to explain it? 

I think it is debatable. 

So do what do you think is the role of language in thinking? Do we think using language, or do we only use language to express already made up thoughts?

Ah, I now have something new for me to find out and learn. 

pearlie