As recently as 1985, babies were operated on without anesthesia because doctors believed they feel no pain!

The author of this paper shows how babies and infants have been treated as lesser beings in the past because of the fact that they haven't developed their full cognitive capacities. People have judged babies' cries as 'random sounds' and their smiles as 'muscle spasms.' 

This seemed to be confirmed through science because babies would be pinched and prodded with needles when they were newborn. Doctors observed that babies reacted more violently as time went on. They thought this meant that the ability to feel pain would develop over time. However, the reason for this was actually because of the anesthesia that the mother had received, and that had been passed on to the baby. 

It wasn't until 1985 where studies on babies showed that not only did they feel pain, some babies were dying because they were being operated on without any anesthesia or anything to prevent the pain!