Experimento social | Uma (in)certa antropologia

ScienceDaily (Aug. 23, 2012) — People will reject an offer of water, even when they are severely thirsty, if they perceive the offer to be unfair, according to a new study funded by the Wellcome Trust. The findings have important implications for understanding how humans make decisions that must balance fairness and self-interest.

It’s been known for some time that when humans bargain for money they have a tendency to reject unfair offers, preferring to let both parties walk away with nothing rather than accept a low offer in the knowledge that their counterpart is taking home more cash.

In contrast, when bargaining for food, our closes relatives chimpanzees will almost always accept an offer regardless of any subjective idea of ‘fairness’.

Researchers at the Wellcome Trust Centre for Neuroimaging at UCL wanted to see whether humans would similarly accept unfair offers if they were bargaining for a basic physiological need, such as food, water or sex.

The team recruited 21 healthy participants and made 11 of them thirsty by drip-feeding them a salty solution, whilst the remainder received an isotonic solution that had a much smaller effect on their level of thirst. To obtain an objective measure of each individual’s need for water, the team measured the salt concentration in their blood. The participants’ subjective perception of how thirsty they were was assessed using a simple rating scale.

The participants then separately took part in an ultimatum game. They were given instructions that two of them had been randomly selected to play a game to decide the split of a 500ml bottle of water that could be consumed immediately. One of them would play the part of ‘Proposer’ and decide how the bottle should be split. The other would be a ‘Responder’ who could either accept the split and so drink the water offered to them, or reject the split so that both parties would get nothing. The participants knew that they would have to wait a full hour after the end of the game before they would have access to water.

In reality, all of the participants played the part of the Responder. They were presented with two glasses of water with a highly unequal offer that they were told was from the Proposer: the glass offered to them contained 62.5ml, an eighth of the original bottle of water, and the other contained the remaining seven eighths that the Proposer wanted to keep for themselves. They had fifteen seconds to decide whether to accept or reject the offer.

The team found that, unlike chimpanzees, the human participants tended to reject the highly unequal offer, and here that was the case even if they were severely thirsty. The participants’ choices were not influenced by how thirsty they actually were, as measured objectively from the blood sample. However, they were more likely to accept the offer if they subjectively felt that they were thirsty.

Dr Nick Wright, who led the study, explains: “Whether or not fairness is a uniquely human motivation has been a source of controversy. These findings show that humans, unlike even our closest relatives chimpanzees, reject an unfair offer of a primary reward like food or water — and will do that even when severely thirsty. However, we also show this fairness motivation is traded-off against self-interest, and that this self-interest is not determined by how their objective need for water but instead by their subjective perception of thirst. These findings are interesting for understanding how subjective feelings of fairness and self-interested need impact on everyday decisions, for example in the labour market.”

Journal Reference:

Nicholas D. Wright, Karen Hodgson, Stephen M. Fleming, Mkael Symmonds, Marc Guitart-Masip, Raymond J. Dolan.Human responses to unfairness with primary rewards and their biological limits. Scientific Reports, 2012; 2 DOI: 10.1038/srep00593

ScienceDaily (Aug. 15, 2012) — Neighbourhood income deprivation has a strong negative effect on altruistic behaviour when measured by a ‘lost letter’ experiment, according to new UCL research published August 15 in PLoS One.

Researchers from UCL Anthropology used the lost letter technique to measure altruism across 20 London neighbourhoods by dropping 300 letters on the pavement and recording whether they arrived at their destination. The stamped letters were addressed by hand to a study author’s home address with a gender neutral name, and were dropped face-up and during rain free weekdays.

The results show a strong negative effect of neighbourhood income deprivation on altruistic behaviour, with an average of 87% of letters dropped in the wealthier neighbourhoods being returned compared to only an average 37% return rate in poorer neighbourhoods.

Co-author Jo Holland said: “This is the first large scale study investigating cooperation in an urban environment using the lost letter technique. This technique, first used in the 1960s by the American social psychologist Stanley Milgram, remains one of the best ways of measuring truly altruistic behaviour, as returning the letter doesn’t benefit that person and actually incurs the small hassle of taking the letter to a post box.

Co-author Professor Ruth Mace added: “Our study attempts to understand how the socio-economic characteristics of a neighbourhood affect the likelihood of people in a neighbourhood acting altruistically towards a stranger. The results show a clear trend, with letters dropped in the poorest neighbourhoods having 91% lower odds of being returned than letters dropped in the wealthiest neighbourhoods. This suggests that those living in poor neighbourhoods are less inclined to behave altruistically toward their neighbours.”

As well as measuring the number of letters returned, the researchers also looked at how other neighbourhood characteristics may help to explain the variation in altruistic behaviour — including ethnic composition and population density — but did not find them to be good predictors of lost letter return.

Corresponding author Antonio Silva said: “The fact that ethnic composition does not play a role on the likelihood of a letter being returned is particularly interesting, as other studies have suggested that ethnic mixing negatively affects social cohesion, but in our sampled London neighbourhoods this does not appear to be true.

“The level of altruism observed in a population is likely to vary according to its context. Our hypothesis that area level socio-economic characteristics could determine the levels of altruism found in individuals living in an area is confirmed by our results. Our overall findings replicate and expand on previous studies which use similar methodology.

“We show in this study that individuals living in poor neighbourhoods are less altruistic than individuals in wealthier neighbourhoods. However, the effect of income deprivation may be confounded by crime, as the poorer neighbourhoods tend to have higher rates crime which may lead to people in those neighbourhoods being generally more suspicious and therefore less likely to pick up a lost letter.

“Further research should focus on attempting to disentangle these two factors, possibly by comparing equally deprived neighbourhoods with different levels of crime. Although this study uses only one measure of altruism and therefore we should be careful in interpreting these findings, it does give us an interesting perspective on altruism in an urban context and provides a sound experimental model on which to base future studies.”