Language allows you to refine your thoughts. Words stand for abstract concepts that you cannot picture otherwise. Let's use that as an example! How would you think of an "abstract concept" without using those words or any others?

So while instinctive thought can be "faster," it cannot be as detailed. And fast, simple thoughts are not going to be "efficient" when dealing with complex subjects.

[[Edit: Another example: It's easy to picture four things. Four apples. Four cars. Four fingers held up on one hand. It's very hard to picture fourteen million two hundred and four thousand six hundred and seventy five things. You need the precision of words to accurately track and plan around things you can't visualize, whether that's large numbers, complex actions and interactions, sequential events over long periods of time, or abstract ideas.]]