These findings add to the mounting evidence that humans are biologically disposed to dislike inequality. That it is subjective self-interest rather than objective need that is traded-off against fairness is important.
Dr Nick Wright
Researchers from the Wellcome Trust Centre for Neuroimaging at University College London (UCL) have found that people reject offers of water, in spite severe thirst, if they perceive that offer to be unfair. The results of the study, funded by the Wellcome Trust, were reported last week in the open access journal Scientific Reports
Dr Nick Wright, a Wellcome Trust Clinical Research Training Fellow at UCL, gave ScienceOmega.com
further insight into the findings of the study and how we can further explore human attitudes to fairness. I began by asking him if the team had expected to find participants so unwilling to accept offers which could only be perceived as unfair.
"Not necessarily," Dr Wright said. "We thought that it might be the case that humans too would ignore unfairness or inequality when they were really thirsty; that is, we expected they would accept anything, however unfair the offer, as chimpanzees do."
Previous studies have demonstrated that chimpanzees – some of our closest relatives – will accept any offer that is made where food is involved, regardless of whether the offer is at all fair. The experiment conducted by Dr Wright and his colleagues therefore aimed to test whether humans would react similarly when faced with an unfair offer concerning a basic physiological need: water.
21 participants were recruited to take part in the study. Of these, 11 had thirstiness induced by the administration of a salty solution and the rest were drip-fed an isotonic solution which had little effect on their level of thirst. The participants’ objective need for water was measured by the salt concentration in their blood, while they rated their thirst subjectively using a simple scale.
The individuals were each told that they would play the part of ‘proposer’ or ‘responder’, but in reality each was a responder. The hypothetical proposer decided how a 500ml bottle of water should be split, and the subject then had to decide whether to accept or reject their decision. They were aware that if they said no, both parties would receive nothing and they would have to wait at least an hour for access to water.
Unlike chimpanzees, the participants in the experiment tended to reject the highly uneven offer of 62.5ml – an eighth of the bottle – even if they were extremely thirsty. Although the objective measure of thirst from the blood sample did not affect the result, their choices were shown to be influenced by how thirsty they described themselves as feeling.
"These findings add to the mounting evidence that humans are biologically disposed to dislike inequality," Dr Wright explained. "That it is subjective self-interest rather than objective need that is traded-off against fairness is important. It helps explain why considering just the objective aspects of bargaining situations will explain only part of the story."
In experiments using money as the bargaining chip, humans have consistently been seen to turn down unfair offers and let both parties walk away with nothing. I asked Dr Wright if our attitude towards fairness differs significantly when dealing with money in comparison to basic physiological needs like food and water.
"Our data show that they are quite similar," he replied. "The big advantage here is that we can examine an individual’s objective need for water using blood tests. The objective ‘need’ for money is clearly more difficult to measure."
The uniqueness of human attitudes to fairness has been a topic of hot debate for a long time, and the results of this study certainly shed some light on the subjective nature of human decision-making, even when it comes to basic resources like water and food. The researchers are optimistic that more detailed answers will be revealed with further study.
"It may be that responses to unfairness in this way are uniquely human," Dr Wright speculated. "We just don't know yet but we can find out, and that is why this field is so exciting! We need to conduct experiments with a range of different species and with a range of different tasks, which will help us delineate the different aspects of fairness that may be exhibited by those different species."