I still don't "buy" that some people don't have an inner voice. In my opinion it's either a misunderstanding of what it means to have an inner voice (it's not the schizophrenic "other person" voice), or people simply lying to appear quirky and special.

If people don't have an inner voice, it also must be the case the some people (these people?) don't have consciousness. It isn't obvious that consciousness is essential to fitness, especially of an inner voice isn't. Some people may be operating as automatons.