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The Origin Of Mistrust, Investigated In Twins

Is distrust the opposite of trust? No, say American researchers. Both feelings have their own origins, and only one is influenced by genes.

Everyone has heard it before — this inner voice that warns us about someone. We distrust a person without knowing them well. But where does this feeling come from? Is distrust perhaps a kind of innate sensor? After all, science has long suspected that trust is, at least in part, genetically determined. So it makes sense to assume this from mistrust as well. However, American scientists have now been able to show that the two feelings are far less closely related than one might think (1).

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For their study, researchers led by Martin Reimann from the University of Arizona examined more than 500 female twins, 324 monozygotic and 210 fraternal. While monozygotic twins are genetically almost identical, the genetic makeup of fraternal twins is only about 50 percent identical. Comparing these two groups helps scientists to understand three things: 1. the influence of genes, 2. the effects of experiences and events that both twins share, and 3. the role of individual experiences and life events.

For this study, the twins had to participate in a money game. In the first version, they had to decide how much of the money they had been given was to be given to another person, not their co-twin. In this way, the scientists wanted to find out how much the twins trusted another person. In a second variant of the game, the aim was to accept any amount of money from another participant as a measure of mistrust.

As to be expected, a comparison of the groups showed that identical twin pairs behaved much more similarly than fraternal pairs in a game of trust. In the variant of mistrust, however, the researchers could not find such an accumulation. The scientists concluded that genes do not play a role in mistrust. In contrast, they calculated the heredity for trust to be 30 percent, i.e., about 30 percent of the differences in trust observed in this study can be explained by genes.

The researchers also calculated ratios for other factors. Experiences and events made by both twins seemed to have an effect of 19 percent on the results of mistrust, but not on the degree of trust shown by the test subjects.

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However, the study shows that individual experience is by far the most important factor influencing both trust (70 percent) and distrust (81 percent). This also means that trust and mistrust are probably not only based on experiences from the first years of life but also develop later. This is because imprinting individual experiences are often only made during later years, when the twins no longer live together.

It remains to be seen whether the individual figures will be confirmed in further studies. The basic trend, however, seems clear: trust and mistrust seem to be two separate characteristics with a partly different history of origin. While both sensations are mainly influenced by experience, trust is also influenced by genes.

The researchers argue that it is now time to investigate which experiences decide whether a person is very suspicious of others. Negative experiences could, for example, be violence by parents, bullying at school, or disappointment among friends.

This is part 37 of a series covering twin health provided by Paul Enck from the Tübingen University Hospital and science writer Nicole Simon. Further studies in twin research can be found at the TwinHealth website. Translation was done with the assistance of DeepL translator.

Reference:

  1. Reimann M, Schilke O, Cook KS. Trust is heritable, whereas distrust is not. Proc Natl Acad Sci USA. 2017;114(27):7007-12.

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