I think Jews and Muslims (and whoever else circumcises their baby boys; and girls in some cultures) do not give much thought to any potential pain a baby maybe experiencing and how this may have an impact to their lives.
There is debate over how early on in life babies can recall memories, including instances of pain. A bunch of researchers (I shall find out who they were, developmental pysch isn't a field I get terribly excited about) did a study into how children/adults who had been circumcised as babies experienced/recalled painful events later on in life. They found that those circumcised in infancy recalled instances in childhood and adulthood (e.g. falling off a bike) more vividly and reported feeling more pain than those who had not been circumcised. The theory behind this finding is that we set up reference points in life to compare experiences (of pain) to.
So, say you get shot and you think that is your most painful experience to date then you will judge how painful any subseqeuent experience is by using the being shot incident as your reference point. Even if babies can not consciously recall being circumcised (there is a phenomenan called childhood amnesia which describes how we seldom recall memories before the age of 3 years) that doesn't mean it doesn't have a longterm impact on their perceptions of pain.
Even if we were to leave aside long term implications of infantile experiences, there is evidence to suggest that babies do fee pain. Here's an accessible paper to read:
http://www.terrylarimore.com/BabiesAndPain.htmlHere's an article on medical circumcision (which is very common in the US amongst non-Muslims/Jews-- I had it done), and it's generally pro-circumcision, seeing it as medically beneficial*, but notice even it makes it clear that the procedure IS painful:
Newborns who have a circumcision without analgesia (for pain relief) respond in ways that strongly suggest that they do feel pain and experience stress. They show changes in heart rate, blood pressure, and oxygen saturation, as well as changes in cortisol levels and behavioral changes. The behavioral changes include crying at the time as well as changes in sleep patterns and mother-child interactions that are temporary and disappear within 24 hours of the procedure.
http://www.medicinenet.com/circumcision_the_surgical_procedure/page2.htm#4isa------------------------------------------------
*
Circumcision may be performed for religious or cultural reasons, or for health reasons. Newborn circumcision is thought to diminish the risk for cancer of the penis and lower the risk for cancer of the cervix in sexual partners. It is also believed to decrease the risk of urinary tract infections in infants and lower the risk of certain sexually transmitted diseases, especially HIV.
Topic: The Psychology of Circumcision...