An insight from the work of behavioural economist/neuroscientist Paul Zak on levels of oxytocin in our blood stream: Reciprocity is more likely for those with high levels of oxytocin.  And most interesting finding: 5% of people will never reciprocate in trust experiments.  He calls those lacking in trust to their fellow humans bastards 🙂  I think this needs to be qualified.  And of course put into context of what trust is good for.

The implication of this claim for SNA could be that; a. some social actors are genetically predisposed to be isolates & b. that social interaction is not only determined by feelings of trust but driven by need & opportunity.  i.e the distribution of trust is not the only force driving social interaction.  And of course that personal social capital can be a reputational resource that can affect the probability of reciprocation, even if an actor is generally mistrusting of others and seeking to exploit the reciprocation of others.