American Scientist

THE ALTRUISTIC URGE: Why We’re Driven to Help Others. Stephanie D. Preston. xvii + 320 pp. Columbia University Press, 2022. $35.

In the preface to her new book, The Altruistic Urge, psychologist Stephanie D. Preston notes that there are many types of altruism and that it would be helpful to have an agreed-upon taxonomy of these types that is based on evidence from biology, psychology, and neuroscience—evidence relating to the way the behavior looks or functions, how it evolved, and how it is mediated in the brain and body. In the book, she marshals this sort of evidence for a type of altruism she views as fundamental: the impulse to help a vulnerable being in need of immediate aid. Humans and other mammals instinctually feel this evolutionarily ancient altruistic urge in very specific situations, she says, because it is biologically rooted in infant caregiving.

Preston uses as a center point for the book a complex experiment on newly maternal female rats and newborn pups that was carried out by physiological psychologist William E. Wilsoncroft in 1969. The maternal rats were put in a Skinner box, where pressing a bar delivered a food pellet down a chute; after the first several bar presses, what came out of the chute was an infant rat rather than a food pellet. The maternal rat would retrieve the pup by the scruff of its neck and put it in an adjacent nest, and then continue relentlessly pressing the bar for hours, each time releasing a pup that would slide down the chute and be retrieved and placed in the nest. The rats obviously found the task extremely rewarding, not just when the pups were their own offspring but even when they had come from another mother. The mothers kept at it as long as the experimenter kept filling up the pup supply, a task he grew tired of before the rats showed any sign of doing so. In later variations of the experiment, similar behavior was demonstrated in virgin females and males, after they had been given time to become accustomed to the pups. Pup retrieval and care activity is Preston’s model for the altruistic urge in mammals, including humans.

The evolutionary advantage of such behavior for a new mother rat is clear: in protecting her offspring, she would be preserving, as the result of kin selection, the multiple genes that gave rise to the behavior. Preston argues that the advantage would also accrue to rats that have not yet given birth and to male helpers at the nest; she thus maintains that the altruistic urge is an instinct hardwired in rat species and other mammals. She holds that such instincts among mammals are homologous (derived from a common ancestor). She has several reasons for doing so: because they are based on morphological similarities across species, including comparable perceptual traits, such as vulnerability; because the brains of humans are similar to those of other animals; because common regions of the brain (such as the amygdala, nucleus accumbens, anterior cingulate cortex, and prefrontal cortex) are activated in rats, humans, and other mammals during caregiving; and because the same neurohormones (such as oxytocin) are engaged across species during prosocial behavior.

Preston draws dramatic evidence for the generality of this kind of altruistic response from a story reported in the Chicago Tribune in 1996 about a three-year-old boy who fell into the gorilla enclosure at the Brookfield Zoo; a gorilla mother scooped up the unconscious boy to protect him from another ape in the same enclosure. The stimulus of a helpless young mammal (the boy), not unlike her own young, urged the gorilla to act altruistically. No one piece of evidence marshaled by Preston is sufficient to make her case as to the homologous foundations of this type of altruistic response, but the accumulated evidence is powerful.

When we see someone in need of aid who is distressed, vulnerable, or childlike, we respond instinctually, without weighing the benefits.

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When the environmental conditions of behavior are similar—when, for example, we hear a baby cry in distress or see pictures of small children in fear and pain during the war in Ukraine—we feel the urge to help and provide comfort, even from afar. Preston identifies the following as triggering signs: being vulnerable, needing immediate aid, displaying distress, and resembling a child (neoteny). When these visual cues appear in a victim, we instinctually respond without weighing the benefits of response, only quickly estimating whether we have a decent chance of success. Thus, when we see a small, elderly lady carrying a load of packages struggling to get through a door, we are inclined immediately to hold the door open, an urge we don’t experience, or at least not to the same degree, if we see a strapping young man with a load of packages.

Preston is very good at providing clinical and experimental evidence for her claims. For example, she cites opera singer and anthropologist William Beeman, who noted that our auditory system is highly attuned to the exact frequency of a baby’s cry (3 to 4 kilohertz), which also corresponds to the most emotion-laden range of a singer’s voice. Moreover, Preston anticipates the kinds of objections that might be made against her theory—for example, that of bystander apathy. She points out that an instinctual urge does not preclude a rapid assessment of chances for success: It would do little good for an individual who cannot swim to jump in a raging river to try to save a drowning person; in such cases, the urge would be suppressed, or it would activate some other type of efforts to save the victim.

Preston recognizes that there are different classes of altruistic response—that some are more passive and others more active. Among the more passive acts of altruism are consolation behaviors of the kind described by the primatologist Frans de Waal, in which one chimpanzee embraces another who has lost a fight with a dominant chimp. Although Preston doesn’t mention this point, consolation can fade into more erotic responses. Pop songs from the 1940s and 1950s suggest the connection between an infant and the beloved (“Everybody loves a baby/That’s why I’m in love with you/Pretty baby, pretty baby”).

Altruism has always been a problem for evolutionary theory, because an altruistic act benefits the recipient and costs the agent something, even if it’s a minimal amount of energy; altruistic acts seem recalcitrant to the assumption that all evolved behavior, under natural selection, must have been directly or indirectly advantageous to the agent. Preston tries to overcome this conundrum by supposing that altruistic behavior initially arose, among mammalian species, in kin selection of infant retrieval and care (hence, to the benefit of the agent), with its fortunes being fostered by a kind of error, namely that signs of an infant in distress would be misapplied—say, to an adult struggling with packages. Yet, over millennia one would expect natural selection to have eliminated such errors, not to have installed them as the basis of altruism. Preston recognizes this objection and tries to mitigate its potency by arguing that such responses are “baked in” and thus can’t be altered; she also posits that “the offspring care mechanism may already be refined to prevent disadvantageous responses.” But such ripostes dodge the objection rather than resolving it.

Charles Darwin had a different way of solving the problem of altruism. In the Descent of Man, Darwin assumed that moral activity, not reason, was the distinguishing trait of human beings and argued that such behavior was grounded in social instincts, namely those promoting altruistic and cooperative behavior. With the advance of intelligence, memory, and language ability, those social instincts became moral urges. But what is the source of altruistic and cooperative behaviors, which rarely benefit individuals or their offspring? Darwin understood that a natural-selection account of individual behavior was precluded. Instead, he proposed that early, protohuman tribes that happened to have more individuals who were cooperative and self- sacrificing would have the advantage over other tribes with fewer such individuals, which would be natural selection applied to the whole community. As this process continued over the ages, cooperative and altruistic behavior, along with intelligence and language ability, would increase, so that moral behavior would come to characterize the advance of civilizations.

Preston rightly inquires of advocates of the group selection model, such as Darwin: What is it that united disparate individuals into a group in the first place? She suggests it might well have been the retrieval-care model of social instincts that helped to mold individuals into a social group—supported, she proposes, by attitudes arising from notions of reciprocal altruism. Darwin was mindful of the parental-care source of social instincts but disdained reciprocal altruism because its motive was ultimately selfish. His theory of group selection made acts of innately driven cooperation and altruism non-selfish for the individual and thus provided a basis for authentically moral behavior—a foundation that did not require a continuing error at the heart of human moral interaction.

Preston has produced an interesting and well-documented theory of human altruistic behavior, which might profitably be augmented by Darwin’s own account of moral capacity.