You guys are failing to understand one critical thing about dress - it's not only outward facing, it's also inward facing.
Back in the 1950s, a lot of sociologists and anthropologists were trying to understand how the Nazis could commit the horrible crimes they did. When they went out and interviewed German civilians, they all commented that the SS officers were kind, family men - men of honor and principal. So what made them into monsters? According to the civilians, it was when they put on the SS officer's uniform. It changed them - changed their demeanor and personalities.
That's clearly an example of dress having a negative overall impact on a person's identity, but the question remains, can professional dress make people behave more professionally? I don't know the answer, but I have a feeling it's probably something to the tune of "it does for some, doesn't make a difference for others".
I would wager to say that there are some folks here who felt more professional as a pilot the first time they strapped the monkey suit on, and that the suit changed them, at least marginally. Not everyone, but perhaps some.