People didn't think human babies could feel pain until the 1980s[1], and commonly did operations w/o anesthetic.
[1]: https://www.newsweek.com/when-doctors-start-using-anesthesia...
[1]: https://www.newsweek.com/when-doctors-start-using-anesthesia...
One memory is that I hit my head on a rough rock when I was at the age of learning walking and little blood flowed through my forehead. In that time, I didn't feel any pain and was curious on why adults and old sister were so "nervous". In my view, they spoke loudly than usual and rushed to me. I didn't know what they were talking about but I could feel they feared for something.
Another memory is that I shot myself on breast by gas gun, and got bruise (I didn't notice that after I grew up and my parents told me). The age might be 2~4 years old. The same as first one, I did not feel any pain but the fear in adults.
ps: When I was 6~7 years old, I shot myself with air gun on arm again. This time I felt the pain. That was fucking hurt.
Surgery on infants without anesthetic has been shown to cause emotional differences in children.
There's no good solution. Doctors were weighing consequences with little data.