What powers do a shrunken head give to the bearer?
My understanding back in school — and I have no idea anymore what book I had read this in — was that the shrunken head was there to ensure that all the strength and bravery the dead man had possessed in life now went to the bearer of the head, and so they would be worn in war-time. Speaking practically, if you saw a fellow with several shrunken heads on his belt, you’d definitely know he’s a man to stay away from if you can.