It's more or less the same priciple, but with dead skin instead of live. Your hair is made up of layers of cuticles (think kinda like a palm tree) and hot water makes them all spread out from eachother, cold water flattens them in to one smooth strand. Hence softer, shinier, and healthier.
I used to like pretty cool showers, ending with turning off the hot flow completely to rinse conditioner out of my hair for the reason above. Lately I'm really getting in to hot showers (despite it now being summer) as it really is a nice, and still very quick, way to get yourself from walking zombie to useful human in the mornings.
<spe> maevie - proving dykes can't fly
<Dor> You're levelling up and gaining more polys!