That all these people submit so willingly to his needle may have something to do with the fact that he is charm personified. A square-jawed, 50-year-old Californian with good hair, a sunny disposition and a media-friendly nickname ("Dr Love"), Zak gives every impression of having been constructed in a laboratory charged with creating the ideal deliverer of TED talks. "For further information, to request an interview, or even just a hug from Dr Love," reads the press release that accompanies his new book, The Moral Molecule, "please contact ..."