I think the most plausible cause of empathy is that it is something that is hardwired into our brains from birth. Many psychologists believe that many higher mammals possess the ability to empathize with another of the same species. It seems that when we see another person in pain several parts of the brain respond. Not only do we recognize that the person is in pain, but the part of the brain that responds to personal pain becomes active. It means that we are somewhat reliving that type of pain vicariously through the other person. This phenomenon is called mirroring, and is has been documented in both kids and adults. A study done by Jean Decety, a neurologist, showed kids from seven to twelve pictures of people getting hurt, and the part of the brain that responded the strongest was the area that related to feeling pain within their own bodies. The doctors also showed the kids pictures of people purposely inflicting pain on others, and when the kids saw these, additional regions lit up that the doctors believe pertain to morals and self-control. This study shows that empathy, by activating a variety of regions, involves a variety of emotions and factors.
Some people believe that empathy is mainly a taugh emotion and something that isn't inately within us. Now, we must turn to the animal kingdom to prove them at least partly wrong. In the 1960s, a series of studies based on emotional and psychological responses were done using rhesus monkeys (such as the famous bonding study where a wire monkey replaced the mother). In this study fifteen monkeys were placed in cages next to each other with two chains; everytime they pulled a chain, food came out, but one chain gave twice as much food. The scientists tweaked it, so that the chain that gave more food also shocked the monkey in the next cage. The monkeys that could possibly deliver the shock, could see the other in pain, and soon, most of the moneys began to take the lesser food amount and some starved themselves, so they wouldn't need to pull the chain with more food. Another study gave mice a chemical that made them have stomach pains, the unaffected mice in the cage with them began to become aggitate and respond to the other's pain. Does this show that animals can be empathetic without ever "learning" it? Beings that are considered lower than humans, can experience empathy without being taught, so are we born with the same wiring?
There is a psychologic disorder called conduct disorder that basically causes the kids to lash out, commit criminal acts, lie for no reason, and act severely aggressive while not showing remorse or empathy. According to recent studies, this may actually be the opposite; they may react aggressively because they feel another person's pain too strongly and don't have the tools to behave appropriately. Dr. Decety repeated his study with the pictures on older teens who had conduct disorder, which should have shown that the areas of the brain that lit up with normal kids wouldn't with kids with CD. The area of the brain that felt the person's pain from a first-person point of view, lit up, but much stronger than the normal kids. A major difference was that the part that was linked to morals and self-control were dim. A possible scenario resulting from these results may be that the kids with CD act aggressively because of the strong negative response they get from seeing others in pain, but lack the self-control and moral reasoning to react like normal children.
It seems that even people who lack the ability to "learn" and act on morals are able to feel empathy even though they can't express it. Animals who aren't told by their parents what empathy is or how to express it, seem to show it towards others of their species. Kids, who are young enough to not be severely affected by society, have the part of the brain that feels pain as well as the moral reasoning area light up upon seeing others hurt. Does this show that empathy is hard wired into our brains through our evolutionary development? Or do we still need to learn how to deal with these emotions to be able to truly feel empathy?