system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do back scratches feel so good while tummy scratches feel weird and awkward?
gpt
Its because the stomach is a vulnerable and exposed part of the body that stores visceral organs.  Think of when a lion attacks its prey; it goes for the neck or rips out the entrails in the abdomen.  Tickling is a way that parents cultivate the defensive/aversion tactics of protecting these areas in the baby.