"We are all here on earth to help others. What I can't figure out is what the others are here for." --W. H. Auden (1)
Whether we are here to help others is a question I've often asked myself, and a question I will not be able to answer while I am still here on earth. Perhaps before I even consider that question, however, I should wonder whether we even can be here to help others: is selflessness really possible? Or is "altruism" merely doing things for others in order to feel good about ourselves? If human altruism exists, how does our neural system deal with it?
The issue of altruism is complicated by the lack of agreement about many aspects of it, including its very definition. The word altruism, which comes from the Italian altrui, was coined in 1851 by August Comte to refer to benevolence (2). Although not everyone agrees today on what precisely altruism entails, the most basic definition is seeking the welfare of others (1). This definition is often extended, however, to include the necessity of some personal sacrifice on the part of the altruist; Edward O. Wilson defined altruism as "self-destructive behavior performed for the benefit of others" (1), (3). There is also an idea of reciprocal altruism, which is self-sacrificing behavior with the expectation that the favor will be returned eventually (4). If this behavior is motivated by the desire for future reward, it does not really fit the generally accepted definitions of altruism.
In nonhuman animals, altruism is mainly seen in the form of one animal sacrificing or risking its life to save another. Studies of animals by researchers such as Hamilton, who worked with bees who sacrifice themselves to allow the queen to produce offspring with their genetic makeup, have led to an evolutionary explanation of altruism (4). One account of altruism in the animal kingdom is kin selection-that an animal will sacrifice its own life only if as a result, its genes have a greater chance of being passed on (4). Kin selection relates to evolutionary advantage according to Hamilton's rule, C/B < b. The ratio of the cost, C (which is the expected loss in reproductive success for the doer) to the benefit for the recipient, B (the gain in reproductive success for the must be less than the probability that the recipient has the same allele, for the altruist gene to survive (5).
Human altruism is much more nuanced than simply risking one's life for another, and cannot be accounted for by a simple application of Hamilton's rule. Many self-sacrificial acts that people perform for each other do not involve a direct risk to their life, and may also involve some benefit to the actor. Additionally, if the recipient of the act is not a relative, Hamilton's rule doe not apply. In fact, there is some question as to whether human altruism actually exists, or whether what we think of as altruism is actually just "enlightened self interest" (3). Many allow for altruistic acts to include benefits to the actor as long as they are the result of behavior by the recipient of the altruistic act, or others, and as long as the actor has no control over receiving these benefits (6). Others argue that all supposed altruism is really motivated by the benefits to the person performing the act. These include material gains, such as a tax deduction for a charitable contribution, a rise in self-esteem for having done something good, and a sense of security that sometime the favor will be returned by the recipient (3). Although not everyone agrees that altruism can be completely pure, the definitions of altruism accepted by those interested in studying it seem to allow for benefit to the donor, as long as the act of self-sacrifice performed for someone else, with benefit to the actor not being a significant motivation.
With human altruism, there is the complication of compassion, which sometimes is confused with altruism. Compassion refers to an emotion, and altruism to an action; although they are connected, one can act altruistically without sharing in the feelings of others, and one can feel compassion without taking altruistic action (7). Arguments are sometimes made against calculation theories of altruism based on the decision to perform an altruistic act, for example jumping into the water to save a drowning child, is not made based on a calculation of genetic inheritance, but rather emotions and feelings of the right thing to do (7). Compassion and altruism both seem to be playing a role in making this decision, and the neurological mechanisms that might play into each of these are hard to separate from each other in evaluating such acts.
The mixing of empathy with altruistic behavior may contribute to an unclear picture of sex differences in altruism. A study of 573 twin pairs found females to be significantly more altruistic than males (8). Several other studies, however, have failed to show such a definitive effect. A study by Dougherty (1983) found that subjects of both genders were more likely to help people who were acting in "appropriate sex roles," and Colaizzi et al. (1984) found that the display of altruism was affected more by the gender of the recipient of the altruistic act than of the subject performing the altruistic act; people were more likely to help women than to help men (9). The sex difference in altruism seen in the twin study may have been influenced by females' tendency to be more empathetic than men; several studies have shown that females tend to care more than males about close relationships and specific people and their immediate situations (9). Behavior altruism may not have been able to be isolated from this empathetic difference; the emotions involved with altruism may be inseparable from the decision to commit an altruistic act.
The attempt to separate compassion from altruism, of emotion from behavior, although it would allow for a more direct examination of behavioral altruism, may in fact be detrimental to a thorough neurological understanding of altruism because of the connection between emotions and cognitive processes. Antonio Damasio addresses the link between emotion and behavioral decisions by arguing against Descartes' notion that thought occurs separately from bodily mechanisms. Damasio suggests instead that emotions are integral to the process of rational decision-making (10). The lower levels of the brain's structure of reason are the same areas that control emotions, as well as providing a connection between the brain and the rest of the body. Damasio elaborates on the connection between emotion and reason with his Somatic Marker Hypothesis-there is a physical signal, a "gut feeling," that warns us about poor cognitive choices before we make them, allowing us to make decisions more quickly and effectively (10). The somatic marker may play a role in altruistic behavior, as well. The positive feeling associated with acting altruistically may be a positive somatic marker of sorts, a response by the nervous system corresponding to the long-term benefits of altruistic behavior (10).
How is altruistic behavior accounted for in the nervous system? In part, a propensity toward altruism is inherited, with genes coding for enzymes that lay neuronal pathways (8). John R. Evans proposes a more complicated neural picture of altruism, one that allows Hamilton's rule to account for human altruism between nonrelatives, through a memetic adaptation of the rule (5). According to his model, memes, neuronally encoded rules for either physical or mental action, transcribe human behavior through their representation of neural stimulation patterns (5). Since these neural pathways must compete for limited neurochemical resources, they undergo a natural selection of sorts, whereby some memes are selected over others for a place in the nervous system (5). As well as being inherited, memes can be horizontally reproduced, evident by our ability to share ideas with each other. As this relates to altruism, someone committing an altruistic act might copy their meme onto the beneficiary's memetic structure. To take into account the possibility of the altruistic meme, along with the gene, will be passed along, Evers proposes that Hamilton's rule be rewritten: C/B = b + c(1-b), where c is the rate of conversion-the probability that the meme will transfer to someone not already carrying it (the non-carrier population represented by 1-b) (5). Through taking into consideration the transfer of behavior rules as well as genetic codes, the memetic application of Hamilton's rule allows for human altruism between nonrelatives.
Can the memetic application of Hamilton's rule account for the neuronal encoding of human altruism? While that is certainly one of the most interesting questions raised about this issue, we may not be ready to answer it, or even to ask it, until we are more thoroughly able to answer some of the preceding questions. Adding the transfer of memes to Hamilton's rule assumes that kin selection is applicable to human altruism, and that we are examining altruism itself and not confusing it with expressions of emotion and empathy. Perhaps more fundamentally, it assumes that human altruism is real, and that we even know what altruism is in the first place. All of these questions need more complete answers before the neuronal encoding of human altruism can be understood.