Fairness expectations and altruistic sharing in 15-month-old human infants.

Marco F H Schmidt,Jessica A Sommerville,Matjaz Perc

doi:10.1371/journal.pone.0023223

Marco F H Schmidt, Jessica A Sommerville + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0023223

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Abstract

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.

Highlights

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 [1,2,3]
Other bargaining games in which adults can choose how much, if any, money to give to another subject showed that over 50% of participants decide to give away their own money and perform an altruistic act [30]
Even altruistic sharing exists in 15-month-olds: one third of infants shared the toy they preferred despite having the option to share a non-preferred toy; and virtually all of these ‘‘altruistic sharers’’ expected third-party fairness when observing a resource allocation situation in our VOE paradigm

Summary

Introduction

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 [1,2,3]. 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 [20,21,22,23] Among these other-regarding preferences are fairness (based on egalitarian motives, e.g., a propensity to share resources ) and altruism (an act costly to oneself and at the same time beneficial to a recipient). Other bargaining games in which adults can choose how much, if any, money to give to another subject (in a one-shot, anonymous setting) showed that over 50% of participants decide to give away their own money and perform an altruistic act [30] These findings suggest that such other-regarding preferences are an entrenched part of human behavior. By assessing fairness and altruism in infants via both a violation-of-expectancy paradigm and behavioral measures, we sought to empirically validate the hypothesized theoretical interdependence between these two constructs [22,24], and to understand the underlying nature of infants’ potential fairness expectations

Results

Discussion

Materials and Methods