Does sharing rewards come naturally to humans? A study published today (July 21) in Nature found that humans do share their rewards equitably with others. There is a rider, though. Equitable sharing comes naturally to children as young as two years and three years only when it involves collaborative or collective work. On the other hand, children were less inclined, or rather rarely distributed their rewards to others when it did not involve collective action.

Socially governed

Previous studies have also shown that sharing of rewards is more commonly seen and to a much greater degree in humans compared with great apes. These studies involving older children showed that “human sharing is governed by social norms of fairness and equity.”

For instance, after a group-hunting session, chimpanzees tend to share the rewards (food) with others only under “pressure of harassment” or “reciprocally” with others. Contrast this with very young children. Equitable distribution of rewards came naturally even to these young ones when they worked together.

In the first set of experiments, one child always ended up getting more rewards (toys), immaterial of the effort being collective or not. In the team effort experiment, both the children had to pull a board that contained two toys on either end. But the study was so designed that despite both children jointly pulling the board using a rope, one child would always end up getting only one toy and the other getting three toys.

The authors found that a child with three toys always gave the unlucky child one toy, thus achieving equity in the rewards. The toy was given “as if one of the possessions [of the unlucky child] was taken away [by the other],” note the authors.

In the second experiment, children were allowed to enter a room that already had the board pulled to the end stage and with the toys unequally distributed on the board (three on one side and one on the other end of the board). The result was on expected lines. The lucky child who got more toys gave away the extra toy to the other more often in the collaborative group than in the no-work group.

Robust study

To make the study more robust, the researchers eliminated the possibility of “initial sense of possession” by providing all the children of both age groups four toys each. They were then made to work collaboratively, in parallel or “no-work.” In the parallel work condition, each child worked in parallel to pull separate boards and gain access to the toys attached to the boards. The toys on the board were of unequal numbers (one and three toys respectively).

Even in this set of experiments, children of both age groups were more inclined to share the extra toy with the unfortunate ones only in the collaborative condition and not in the parallel or “no-work” conditions.

The final set of experiments involved multiple trials. The multiple trial experiment was designed to eliminate the fear factor — the supposition that the other child who ended up getting fewer toys would not co-operate in pulling the rope in the successive trials.

Even this study showed that equitable distribution of toys happened only when children worked as teams and not when they performed the task in parallel.

“These studies show that collaborative work encourages equal sharing in children much more than does working in parallel,” state the authors.

The highlight of the present study is the use of chimpanzees to compare and contrast the reward-sharing attitude. Chimpanzees by nature are not true collaborative foragers. Hence no difference should ideally be seen, be it collaborative or ‘no-work' condition.

Though the experimental setup was quite different compared with children, the principle was the same – the lucky ones ended up getting more rewards (in this case, food).

In all three conditions, the lucky apes were less likely to equitably share the rewards with others.

Unlike older children who can understand the connection between work and reward, two- and three-year-old children involved in the current study may not fully understand and appreciate the connection between the two. Yet, they consistently showed the tendency to share their unequal rewards with their unlucky partners in all cases involving team work.

Is there a bigger lesson to be learnt from this study?

This article was re-edited for clarity.

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