The following article discusses just that:
The first way was: "How important is it to you to vote in the upcoming election?"
The next day, 82% of the people who answered that question actually went out and voted.
The second version of the questionnaire instead said: "How important is it to you to be a voter in the upcoming election?"
96% of those people voted.
The researcher did three versions of this study, and the results were robust: Yes, wording matters. By using a noun instead of a verb, the questionnaire was able to encourage people to identify more strongly with the idea of being someone who votes.
The article is worth reading because it outlines why the researcher thinks this works--what the psychology behind the effect is--and that may give you ideas for how to reveal character in your writing. The rule of thumb is that when someone says, "I am a [noun]", they care more deeply than someone who says, "I [verb]."
And since I'm discussing the power of words, here's an interesting article on the predictive power of words. It may be possible, by analyzing the wording used by journalists talking about the economy, to predict some of the behaviour of the stock market: