I recently did a battery of tests from the Johnson O'Connor Research Foundation (www.jocrf.org), and they were very keen on vocabulary size as an indicator of workplace success. The idea was that it was an excellent predictor of achievement across a wide variety of different fields. It was less clear which way the causation runs here — does a bigger vocabulary actually make you more successful, by expanding your mind, impressing your clients and colleagues, etc.? Or are people with big vocabularies smarter to begin with and therefor more likely to succeed?

I'm wondering, does anyone either know of any real research on this or have any personal anecdotes about how learning more vocabulary made them more successful?