Our current investigation used a design that builds upon and goes beyond related investigations with infants 9, 25, 30, 31, 32, 33, 34, 35 (Supplementary Information Note 2). Moreover, we tested this idea under evolutionarily relevant conditions designed to increase hunger (Experiment 2). Our investigation experimentally tested whether human infants, at 19 months of age, in the absence of any verbal request, spontaneously, repeatedly, and swiftly give away desirable food to a begging stranger (Experiment 1). ![]() Thus, we explored whether the expression of human infants’ altruistic food transfer behavior to a stranger is related to these types of prior experiences. Prior work has also suggested that sibling experience provides a context for the development of cooperative skills 29. A leading hypothesis from social psychology is that families from different cultures tend to vary in the value they place on being a harmonious, empathic, and “other-regarding” group member 26, 27-and this may be associated with childrearing practices that support the expression of altruistic behavior 26, 28. We used a nonverbal, out-of-reach object test 9, 15, which in the future could be adapted and applied with non-human primates.Īlongside the idea that altruistic food transfer occurs more readily among humans than non-human primates, prior work has examined possible social and cultural contributors to the expression of altruistic helping behavior in human adults 20, 21, 22 and children 23, 24, 25. In light of these patterns, we sought to test whether human infants readily and repeatedly engage in altruistic food transfer to a stranger, and do so when their favorite foods are involved and the motivation for eating the food is induced through an experimental manipulation (Experiment 2). Bonobos share food under many circumstances 14, 15, 16, 17, 18, 19 (Supplementary Information Note 1), but it is not clear how readily they hand over immediately edible, high-value food items in their possession (e.g., a piece of fruit, cracked nuts) rather than eating it themselves. The sociality profile of bonobos differs from chimpanzees 14, 15. Although chimpanzees hand over common objects 9, they do not use this ability to actively transfer nutritious, calorie-rich natural foods such as bananas 10. 452) 8 and that “voluntary handing over of food is virtually absent” (p. Based on a comprehensive review of field and laboratory studies, evolutionary biologists have suggested that episodes of food sharing among chimpanzees are “best regarded as a passive process of selective relinquishment” (p. This altruistic response toward those in want of food has not been demonstrated by chimpanzees, even though this topic has attracted a great deal of study using a wide range of different paradigms 1, 8, 9, 10, 11, 12, 13. Human adults, both in hunter-gatherer and industrialized contexts 5, 6, have developed customs and institutions to provide needy people with food even when it is scarce and the donator needs the food themselves 7. A particularly meaningful category of resources involves caloric benefits-food. For example, adults give away precious resources to strangers, even when the cost is considerable 4. Human adults engage in types of altruistic behavior not seen in other animals 1, 2, 3. Social experience variables moderated the expression of this infant altruistic behavior, suggesting malleability. Here we show that in a nonverbal test, 19-month-old human infants repeatedly and spontaneously transferred high-value, nutritious natural food to a stranger (Experiment 1) and more critically, did so after an experimental manipulation that imposed a feeding delay (Experiment 2), which increased their own motivation to eat the food. Our closest living primate relatives, chimpanzees ( Pan troglodytes) and bonobos ( Pan paniscus), exhibit notable constraints on the proclivity to engage in such food transfer (particularly chimpanzees), although they share many social-cognitive commonalities with humans. ![]() Human adults engage in this form of altruistic behavior during times of war and famine, when giving food to others threatens one’s own survival. Engaging in altruistic food transfer, instead of keeping the food, is costly, because it reduces the caloric intake of the benefactor vis-à-vis the beneficiary. A distinctively human form of altruistic behavior involves handing nutritious food to needy strangers, even when one desires the food. Altruistic behavior entails giving valuable benefits to others while incurring a personal cost.
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