James Katz at Rutgers fears that cyber-nomads are “hollowing them out”. It is becoming commonplace for a café to be full of people with headphones on, speaking on their mobile phones or laptops and hacking away at their keyboards, more engaged with their e-mail inbox than with the people touching their elbows. These places are “physically inhabited but psychologically evacuated”, says Mr Katz, which leaves people feeling “more isolated than they would be if the café were merely empty”. That is because the “physical presence of other human beings is psychologically and neurologically arousing” but now produces no reward. Quite simply, he says, we have not evolved biologically to be happy in these situations.