Social trust: which direction is the causal relationship with socio-economic status?

Social trust is important to the cohesiveness of a community. Empirically, people with high levels of social trust tend to be doing pretty well for themselves, which raises the question: does a lack of social trust keep people poor, or is it that being rich people helps people to trust others around them more? This is the question in the December 2015 article published in Political Psychology titled "Changes in Income Predict Change in Social Trust: A Longitudinal Analysis", by Mark Brandt, Geoffrey Wetherell, and P. J. Henry.

Some researchers think that people with low social status tend to adopt a more defensive mindset due to constant threats to their self-worth arising from their low social status. African Americans who expect to be rejected because of their race experience distrust other people more than African Americans without that expectation. Conversely, rich people have trustworthy social networks to rely on, obviously have had good social experiences in the past that led to their presently having a lot of money, and also have the financial resources to fall back on if they take some kind of social risk and fail.

On the other hand, although trusting is risky, in the long run in prisoners dilemmas games it’s a good strategy. Authors said that people with more social trust are more likely to build social capital, citing a study that suggested the exact reverse, that civic participation leads to interpersonal trust rather than the other way around (Brehm & Rahn, 1997). So maybe they have less prior evidence for the “higher trust causes higher status” hypothesis than they thought. The authors look at longitudinal data from the US and the UK to try to see lagged changes over time. They’re doing something strange with the data in calculating the average of two different measures that they say have different effects. 

They could have tested whether income at T1 is correlated with social trust at T2. Instead, they looked at whether the change in income from T1 to T2 predicted the the change in social trust from T2 to T3. In the US sample, they found an effect of an increase in income between 2000 to 2002 to on increase in social trust between 2002 or 2004. Seems there is a lot that could cause this kind of increase. In the British sample there was an effect, when covariates were not controlled for, but it wasn’t strong. However there was a consistent lack of any sign of a pathway from social trust to income, which makes for a nice contrast.

The effects don’t seem incredibly compelling and the authors could have dug down more with the covariates to see which if any mediated the social trust relationships. But if we overlooked this, it seems like their results show an effect of income on social trust, which is similar to the first of two hypotheses described and the only one for which they seem to have found prior research supporting.

The authors acknowledge that limitations of the design, though not the limitations of the effect size or level of significance.