The question was not intended to be contentious, Sean.
It's probably something that might affect those who tend not to wear a helmet but then have to for certain events for example. If you've never ridden without a helmet then you're more used to the effect and counter it without thinking it about it (or not).
Apparently research has been done on the wearing of helmets in cricket (!) which has found it can contribut to a loss of concentration
From what everyone is saying though it looks like I'm going to have to stick my hair under the water butts at feeding stations
And yes, Sean, please do NOT wear white shorts