Take one man who likes his sandwich made thusly: Two slices of bread, mayo and mustard spread ON THE BREAD, meat and cheese between the bread.
Add one woman who likes her sandwich made thusly: Two slices of bread, butter (if available) spread on the bread, meat and cheese between the bread, mayo and mustard spread ON THE MEAT.
These two, in 20 years of marriage, will produce:
A child who makes her sandwiches exactly the same way the man does, and turns up her little German nose and sneers at anyone who suggests that any other way is acceptable.
One other child who makes his sandwiches like so: Two slices of bread, mayo spread ON THE BREAD, meat and cheese between the bread, and mustard spread ON THE MEAT. And also two ancillary slices of muenster cheese spread with mustard, to eat as a side dish IF his mother doesn't catch him first and put a stop to his evil plan.
Make of that what you will...and wait with bated breath for the Amazing Travelogue of Randomness which will be posted in the foreseeable future...