I think you are referring to poults (young turkey), pullets are young female chickens.

I don't know of a scientific method, we have 4 turkeys now about 4 months old, the biggest difference we saw with the Toms was the size (much bigger). Also the Toms seem to have more squabbles between themselves, our lone hen doesn't bother herself with such childish behavior :)

Their head and their wattles, which is a fleshy growth under their chin, will be larger. His snood, which is a fleshy growth on top of his bill, will be longer and hang down the side of his face. Toms are the only ones who strut and gobble.

Hope this helps.
-Sheila