People interpret "one kid is a boy" as "first-born is a boy" in my example above (i.e. they selectively choose which kid is the "one kid" -- the one which is a

People interpret "one kid is a boy" as "first-born is a boy" in my example above (i.e. they selectively choose which kid is the "one kid" -- the one which is a boy), which yields 1/2. People seem to be good at enumerating the "probability space" quite well. They just don't understand why the dimensions are what they are.