Thanks for the clarification. However, I remain confused. The definition of higher level functioning version of pain seems tautological and at odds with commonsense observations. The definition of higher functioning definition of pain suggests that one and two year olds do not feel pain. This on the face of it is absurd as any parent with a teething baby well knows. Also what does "fully developed" mean? A baby's hand is a hand, but it obviously is less developed than an adult's. Does this mean that it is not a hand?
Moreover, if there are two definitions and one is more objectively measurable than the other, shouldn't we go with the more measurable, at least until we can arrive at a less arbitrary definition?
Clearly there are some tricky definitional issues here - but IMHO Dr. Derbyshire's review article remains highly problematic and his policy conclusions clearly questionable and necessarily dictated by his very definition of pain.
Obviously a grasshopper feels pain as well -- it certainly reacts as though it does. If we are talking about the ability to consciously perceive pain and reflect on that perception, we normally restrict those types of capabilities (at least in our cognitive models) to organisms with well-developed higher brain function. Humans do not fully acquire their higher brain function until 12-24 months of age, something there is both direct physiological evidence of (undeveloped brain tissue) and indirect evidence of (lack of certain types of high-level cognitive capabilities).
Also what does "fully developed" mean? A baby's hand is a hand, but it obviously is less developed than an adult's. Does this mean that it is not a hand?
A human is born with little more than a functioning brain stem, pound for pound, maybe something like a lizard's central nervous system. The life support system, in other words. Unlike a baby's hand, which is generally functional but small, the baby's head only holds scaffolding upon which the brain tissue will grow after birth. This is absolutely necessary, since a baby's head already pushes the limits of what can reasonably fit down the birth canal. After birth, the higher brain rapidly starts to grow and assemble itself on the pre-natal scaffolding. As the brain tissue assembles itself, high-level cognitive function starts to be expressed.
There is tons of very solid evidence that the scaffolding a baby is born with cannot support cognitive function. The most poignant being that there are a number of neurological diseases in adult humans that will effectively revert the brain to something similar to that scaffolding state, all of which are marked by severe cognitive degeneration. Humans that end up in a state like a baby is born in lose all direct and indirect signs of higher cognitive function.
So the short answer is, a baby is born with many organs that are merely small versions of the adult one. However, the baby is only born with the scaffolding for a high functioning brain plus a basic animal life support system to keep the heart beating. This is actually a really neat trick -- it allows humans to have a ridiculously large brain that otherwise would not be supportable via normal reproductive processes.