"Consumers are probably pretty unhappy to notice that their payroll taxes have gone up, " said David Sloan, an economist at New York-based researchers 4Cast.

BBC: US housing recovery gains steam

This is a view put forward originally by Charles Darwin, but revived in modern times by the biologists David Sloan Wilson, at Bimghamton University, and Edward O.

CNN: Why we love to lose ourselves in religion

David Sloan Wilson, of Binghamton University, in New York state, agrees with that point, but reckons the actual moral sense an individual acquires is not arbitrary, as a language is, but is functionally adapted to circumstances.

ECONOMIST: Human evolution