In the event, I escape our encounter unpunctured, but plenty of people don't: Zak's work, which he refers to as "vampire studies", has involved extracting blood from a bride and groom on their wedding day; from people who have just had massages, or been dancing; from Quakers, before and after their silent worship; and from tribal warriors in Papua New Guinea as they prepare to perform traditional rituals.
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 ..."