Fairness Expectations and Altruistic Sharing in 15-Month-Old Human Infants
Citation: Schmidt MFH, Sommerville JA (
Fairness Expectations and Altruistic Sharing in 15-Month-Old Human Infants
Marco F. H. Schmidt 0
Jessica A. Sommerville 0
Matjaz Perc, University of Maribor, Slovenia
0 1 Department of Developmental and Comparative Psychology, Max Planck Institute for Evolutionary Anthropology , Leipzig, Germany , 2 Department of Psychology and Institute for Learning and Brain Sciences, University of Washington , Seattle, Washington , United States of America
Human cooperation is a key driving force behind the evolutionary success of our hominin lineage. At the proximate level, biologists and social scientists have identified other-regarding preferences - such as fairness based on egalitarian motives, and altruism - as likely candidates for fostering large-scale cooperation. A critical question concerns the ontogenetic origins of these constituents of cooperative behavior, as well as whether they emerge independently or in an interrelated fashion. The answer to this question will shed light on the interdisciplinary debate regarding the significance of such preferences for explaining how humans become such cooperative beings. We investigated 15-month-old infants' sensitivity to fairness, and their altruistic behavior, assessed via infants' reactions to a third-party resource distribution task, and via a sharing task. Our results challenge current models of the development of fairness and altruism in two ways. First, in contrast to past work suggesting that fairness and altruism may not emerge until early to mid-childhood, 15-month-old infants are sensitive to fairness and can engage in altruistic sharing. Second, infants' degree of sensitivity to fairness as a third-party observer was related to whether they shared toys altruistically or selfishly, indicating that moral evaluations and prosocial behavior are heavily interconnected from early in development. Our results present the first evidence that the roots of a basic sense of fairness and altruism can be found in infancy, and that these other-regarding preferences develop in a parallel and interwoven fashion. These findings support arguments for an evolutionary basis - most likely in dialectical manner including both biological and cultural mechanisms - of human egalitarianism given the rapidly developing nature of other-regarding preferences and their role in the evolution of human-specific forms of cooperation. Future work of this kind will help determine to what extent uniquely human sociality and morality depend on other-regarding preferences emerging early in life.
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Funding: This work was supported in part by a grant to MFH Schmidt from the Ludwig Maximilian University of Munich (stipend program Hochschule International),
and by a grant to Dr. Sommerville from the National Institute of Child Health and Development (grant #R03 HD053616-01). The funders had no role in study
design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Since Darwin, the evolutionary emergence and stability of
human cooperation which presents an outlier in the animal
kingdom in terms of its scale has puzzled biologists and social
scientists [13]. This is due to the paradoxical nature of
cooperative activities: they are frequently costly to the individual
without yielding any direct benefits. Traditionally, natural
selection is assumed to favor competition among conspecifics
[1,4], or, even more fundamentally, between alleles [3,5], but the
fact that virtually all human societies are based on cooperation
(often among genetically unrelated individuals) has led researchers
to identify mechanisms that allowed cooperation to emerge and
persist. Nowak [6] proposed five such mechanisms: kin selection,
direct reciprocity, indirect reciprocity (based on reputation),
network reciprocity [7,8], and group selection. Further
mechanisms that have been suggested to enforce cooperation are
punishment including peer- and pool-punishment [915], reward
[1618], and policing [19].
In addition to recognizing ultimate mechanisms that explain
why and under which conditions cooperative behaviors are
adaptive, a critical charge in building a scientific understanding
of human cooperative tendencies is identifying psychological
dispositions and traits that enable the operation of such
mechanisms in the first place. As such, empirical research using
psychological methods is very important for understanding how
humans become such cooperative beings over the course of
ontogeny. Recently, a range of prosocial dispositional attitudes or
other-regarding preferences have been identified and promoted
as likely candidates to explain why human cooperation has been
maintained and developed to a large scale [2023]. Among these
other-regarding preferences are fairness (based on egalitarian
motives, e.g., a propensity to share resources equally) and altruism
(an act (...truncated)