1. Introduction1.1. Biological compatibilityAltruism and selfishness, like free will and determinism,seem to be polar opposites. Yet, as with free will and deter-minism (Dennett 1984), the apparent incompatibility maybe challenged by various forms of compatibility. From a bi-ological viewpoint selfishness translates into survival value.Evolutionary biologists have been able to reconcile altruismwith selfishness by showing how a biological structure me-diating altruistic behavior could have evolved. (The nextsection will briefly summarize one such demonstration.)This structure is assumed to be more complex than ordinarymechanisms that mediate selfish behavior but in essence isno different from them. The gazelle that moves toward thelion (putting itself in danger but showing other gazelleswhere the lion is) may thus be seen as acting according tothe same principles as the gazelle that takes a drink of wa-ter when it is thirsty. The desire to move toward the lionstands beside the desire to drink.Evolutionary biologists do not conceive of behavior itselfas being passed from generation to generation; rather, somemechanism, in this case an internal mechanism – a struc-ture of nervous connections in the brain – is hypothesizedto be the evolving entity. Altruism as it appears in behavioris conceived as the action of that mechanism developedover the lifetime of the organism. Tooby and Cosmides(1996, p. 125) compare the structure of the altruism mech-anism to that of the eye: “We think that such adaptationswill frequently require complex computations and suspectthat at least some adaptations for altruism may turn out torival the complexity of the eye.”This biological compatibility makes contact with moderncognitive and physiological psychology (Sober & Wilson1998). Cognitive psychology attempts to infer the mecha-nism’s principles of action (its software) from behavioral ob-servation and manipulation, while physiological psychologyattempts to investigate the mechanism itself (its hardware).From the biological viewpoint, altruistic acts differ fromselfish acts by virtue of differing internal mediating mech-anisms; altruism becomes a motive like any other. In thisview, a person leaves a tip in a restaurant to which he willnever return because of a desire for fairness or justice, a de-sire generated by the restaurant situation and the altruisticmechanism within him, which is satisfied by the act of leav-ing the tip. Similarly, he eats and drinks at the restaurantbecause of desires generated by internal mechanisms ofhunger and thirst. For the biologist, Person A’s altruistic be-havior (behavior that benefits others at a cost to A) wouldbe fully explained if Person A were shown to possess therequisite internal altruistic mechanism. Once the mecha-nism were understood, no further explanation would be re-quired.The problem with this conception, from a behavioralviewpoint, is not that it postulates an internal mechanism asBEHAVIORAL AND BRAIN SCIENCES (2002) 25, 239–296Printed in the United States of America© 2002 Cambridge University Press 0140-525X/02 $12.50239Altruism and selfishnessHoward RachlinPsychology Department, State University of New York, Stony Brook, [email protected]: Many situations in human life present choices between (a) narrowly preferred particular alternatives and (b) narrowly lesspreferred (or aversive) particular alternatives that nevertheless form part of highly preferred abstract behavioral patterns. Such alterna-tives characterize problems of self-control. For example, at any given moment, a person may accept alcoholic drinks yet also prefer be-ing sober to being drunk over the next few days. Other situations present choices between (a) alternatives beneficial to an individual and(b) alternatives that are less beneficial (or harmful) to the individual that would nevertheless be beneficial if chosen by many individu-als. Such alternatives characterize problems of social cooperation; choices of the latter alternative are generally considered to be altru-istic. Altruism, like self-control, is a valuable temporally-extended pattern of behavior. Like self-control, altruism may be learned andmaintained over an individual’s lifetime. It needs no special inherited mechanism. Individual acts of altruism, each of which may be ofno benefit (or of possible harm) to the actor, may nevertheless be beneficial when repeated over time. However, because each selfishdecision is individually preferred to each altruistic decision, people can benefit from altruistic behavior only when they are committedto an altruistic pattern of acts and refuse to make decisions on a case-by-case basis.Keywords: addiction; altruism; commitment; cooperation; defection; egoism; impulsiveness; patterning; prisoner’s dilemma; recipro-cation; reinforcement; selfishness; self-controlHoward Rachlin obtained a PhD at Harvard Uni-versity in 1965. He is currently a Distinguished Profes-sor of Psychology at the State University of New York atStony Brook. He has written six books including Behav-ior and Mind (1994) and The Science of Self-Control(2000). He has published three previous target articlesin BBS: “Maximization theory in behavioral psychol-ogy,” with John Kagel, Ray Battalio, and Leonard Green(1981), “Pain and behavior” (1985), and “Self-control:beyond commitment” (1995).such. (After all, no behavior is possible without internalneural structure.) The problem is that in focusing on an in-herited internal mechanism, the role of learning over an or-ganism’s lifetime tends to get ignored. To develop normally,eyes have to interact with the environment. But we inheritgood eyesight or bad eyesight. If our altruism mechanismsare like our visual mechanisms we are doomed to be moreor less selfish depending on our genetic inheritance. This isa sort of genetic version of Calvinism. Experience might aid in the development of altruistic mechanisms. Environ-mental constraints imposed by social institutions – family,religion, government – might act on selfish motives (likeglasses on eyesight) to make them conform to social good.But altruistic behavior as such, according to biological the-ory, would depend (as eyesight depends) much more ongenes than on experience.The present article, does not deny the existence of suchmechanisms. A large part of human altruism and a still largerpart of nonhuman altruism may well be explained in termsof inherited mechanisms