We provide direct evidence that people with strong family ties have a lower level of trust in strangers than people with weak family ties, and argue that this association is causal. We also investigate the mechanisms that underlie this effect, and provide evidence that these revolve around the level of outward exposure: factors that limit exposure limit subjects’ experience as well as motivation to deal with strangers.
Society benefits from strong nuclear families as children need parents to raise them. But the benefit from strong extended families (extending out to cousins and beyond) is not clear.
Which groups have especially strong family ties? People who engage in consanguineous (cousin) marriage. You will see at that link that Middle Eastern cultures have weak and corrupt governments and, not coincidentally, high rates of consanguineous marriage. To the extent that immigration policies let in large numbers of Muslims who engage in the same practice in Western societies we will suffer from a lower trust society and more corruption. Actually, immigration reduces trust and social capital (and those of strong liberal faith are reluctant to let us know this) even without consanguineous marriage. Consanguineous marriage makes the problem much worse as it promotes divisions down to the scale of extended families.