Laurie Taylor asks why so many Islamist extremists come from an engineering background. He talks to Steffen Hertog, Associate Professor of Comparative Politics at the London School of Economics, about a new study which finds that Islamist and right-wing extremism have more in common than either does with left-wing extremism, in which engineers are absent while social scientists and humanities students are prominent. Is there a mindset susceptible to certain types of extremism? They're joined by Raffaello Pantucci, Director of International Security Studies at the Royal United Services Institute.