One of the faults I find in much social research is that ideologically motivated researchers assume what they wish to prove, and then confirm thier biases. This seems to be a good example.

Participants in laboratory games are often willing to alter others’ incomes at a cost to themselves, and this behaviour has the effect of promoting cooperation1–3. What motivates this action is unclear: punishment and reward aimed at promoting cooperation cannot be distinguished from attempts to produce equality4. To understand costly taking and costly giving, we create an experimental game that isolates egalitarian motives. The results show that subjects reduce and augment others’ incomes, at a personal cost, even when there is no cooperative behaviour to be reinforced. Furthermore, the size and frequency of income alterations are strongly influenced by inequality. Emotions towards top earners become increasingly negative as inequality increases, and those who express these emotions spend more to reduce above-average earners’ incomes and to increase below-average earners’ incomes. The results suggest that egalitarian motives affect income-altering behaviours, and may therefore be an important factor underlying the evolution of strong reciprocity5 and, hence, cooperation in humans.

So, they gathered 120 students from U.C. Davis - a group exceedingly likely to share the researchers' political biases - and demonstrated that they did seem to share those biases.

I find the work exceedingly unconvincing. It may be that the members of this experimental group cannot distinguish between true cooperation and egalitarian political motivations, but that says little if anything about humans in general. It's comparable to testing a group of US Marine corps gunnery sergeants for male aggression. Yes, they are aggressive. They would not be there if they were not aggressive, much like UC Davis students are selected for certain political views. Also, in both cases the selected characteristics are reinforced by training and indoctrination, which weeds out those not well suited to the local norms.

But that's just the beginning of the nonsensical experimental design.

Each player receives a sum of money randomly generated by a computer. Subjects are shown the payoffs of other group members for that round and are then provided an opportunity to give ‘negative’ or ‘positive’ tokens to other players. Each negative token reduces the purchaser’s payoff by one monetary unit (MU) and decreases the payoff of a targeted individual by three MUs; positive tokens decrease the purchaser’s payoff by one monetary unit (MU) and increase the targeted individual’s payoff by threeMUs. Groups are randomized after each round to prevent reputation from influencing decisions; interactions between players are strictly anonymous and subjects know this. Also, by allowing participants more than one behavioural alternative, the experiment eliminates possible experimenter demand effects12—if subjects were only permitted to punish, they might engage in this behaviour because they believe it is what the experimenters want. . .

The size of income alterations varied with the relative income of the recipient (Fig. 1). Individuals who earned considerably more than other members of their group were heavily penalized. Subjects who earned ten MUs more than the group average received a mean of 8.9 negative tokens compared to 1.6 for those who earned at least ten MUs less than the group. In contrast, individuals who earned considerably less than other group members received sizeable gifts. Subjects who earned ten MUs more than the group average received a mean of 4 positive tokens compared to 11.1 for those who earned at least ten MUs less than the group. Individual spending decisions also suggest that subjects were influenced by concerns for inequality.

So, a group of lottery winners and losers are given the power to loot one another. There is no concept of merit or effort to cloud the pure randomness of economic status. If you have plenty and I have little it is solely because you were luckier than I.

To elicit emotional reactions, we presented subjects hypothetical scenarios in which they encountered group members who obtained higher payoffs than they did (see Methods). Subjects were then asked to indicate on a seven-point scale whether they felt annoyed or angry (1, ‘not at all’; 7, ‘very’) by the other individual. In the ‘highinequality’ scenario, subjects were told they encountered an individual whose payoff was considerably greater than their own. This scenario generated much annoyance: 75% of the subjects claimed to be at least somewhat annoyed, whereas 41% indicated a high level (4 or more) of annoyance. Many subjects (52%) also indicated that they felt at least some anger towards the top earner. In the ‘low-inequality’ scenario, differences between subjects’ incomes was smaller, and there was significantly less anger (Wilcoxon signed rank test, P, 0.0001) and annoyance (P,0.0001). Only 46% indicated they were annoyed and 27% indicated they were angry. Individuals apparently feel negative emotions towards high earners and the intensity of these emotions increases with income inequality.

This seems to be the indignation of emotionally damaged inmates of unhappy institutions . . . like universities. See Business Envy and DWIM for discussion of the emotional problems of academics outraged by capitalism since it does not mete out status and rewards in accordance with their sense of superiority and entitlement.

I think that the researchers are confused. Their claim that "punishment and reward aimed at promoting cooperation cannot be distinguished from attempts to produce equality" is bunk. The earlier work of Fehr, Fischbacher, Gintis, Boyd and others that identified punishment of cheats, as well as those who fail to punish cheats, as the ratchet that enlarges the size of cooperative groups above that of the small band of primitves where such behaviors have adaptive advantages compared to groups that do not, is more compelling. There is no similarly strong egalitarian motivation except among those who have been schooled to believe so.

Humans do not object to high status individuals who earned their places. Indeed, they admire them. This seems to also be an evolved primate behavior. Chimps, IIRC, will trade food for an opportunity to just look at photos of high status troop members. There may be some ambitious or disgruntled troop members who would rather bite the high status chimp's fingers off, but they are the exception.