http://www.slate.com/articles/health_and_science/human_natur...
It is almost in the same line of thinking that infants are not capable of feeling pain and why some operations on them were done without anesthesia:
http://www.nytimes.com/1987/12/17/opinion/l-why-infant-surge...
I believe some operations on infants are still being done without it:
http://gizmodo.com/why-are-so-many-newborns-still-being-deni...
"to this day, many procedures are performed on newborns without the benefit of analgesics. That’s largely because of an enduring misconception in the medical community that newborns don’t feel pain like adults."