The reasoning is that dairy has fats in it that will interact with the hair oils and enable them to be washed out. Based on that reasoning, NON-fat yogurt might not be the best test subject, but it's what's in the fridge.
Post-shower P.S.: Washing your hair with yogurt feels exactly how you would expect it to feel. Except colder because it comes right out of the fridge.I applied about 3T of yogurt to dry hair and worked it in, then left it there for a couple of minutes while I brushed my teeth. It rinsed out easily, but my hair feels pretty oily still, so I'm guessing that it didn't work.