Scientists from Oxford University have just conducted a study showing that babies do indeed feel pain. In MRI scans, 18 of the 20 brain regions associated with pain in adults were active in the infants' brains as well. The study also suggested that babies have a lower threshold to pain and may in fact be more sensitive than adults. http://www.theguardian.com/science/2015/apr/21/babies-feel-pain-like-adults-mri-scan-study-suggests
Ah, yes, science, you are a little behind a mother's intuition on this one... babies aren't whiny for no reason at all. In fact, I believe some babies even experience existential duress and are quite miserable, in spite of all good intentions of the parents.
This life is cold (or too hot), loud, bright... from a dark, relatively quiet and quite cushy, known environment to THIS... who wouldn't be miserable? My daughter had colic very badly for the first 8 or 9 months and we tried EVERYthing. The only thing I could come up with was the fact that she simply did not like being here. And I didn't blame her.
Babies and children are natural scientists and philosophers, exploring the world around them. It makes sense as their first wordless thoughts arise from their response and reaction to their environment that some of those are rather unpleasant sensations and even cause (short-term) unpleasant memories. They cannot speak, they can only communicate by crying their needs. And when all their physical and seeming emotional needs have been met, and they are still crying, what more can one do than suppose that there is a psychological phenomenon going on?
While the good indubitably gets imprinted upon the wee one's mind and brain in healthy upbringings, eventually outpacing those first magnified responses and sensitivity to basic environmental stimuli, the negative responses generally dull in reactive sensitivity as the baby becomes adjusted to the world. The colic gradually dissipates and the child is more engaged with the world.
So perhaps one day we will research this in greater detail. I myself suffer, and have suffered at the hand of exquisite existential pain since I was five years old (that I can remember). This is perhaps a genetic quirk from nature, and one that I have often wondered if I have not passed down to my own. Even so, I have often wondered if colicky babies, too, simply experience negative psychological feedback to those first overwhelming stimuli in comparison to their previously known environs.