title: Prices need no preferences: social trends determine decisions in experimental markets for pain relief.
abstract: OBJECTIVE
  A standard view in health economics is that, although there is no market that determines the "prices" for health states, people can nonetheless associate health states with monetary values (or other scales, such as quality adjusted life year [QALYs] and disability adjusted life year [DALYs]). Such valuations can be used to shape health policy, and a major research challenge is to elicit such values from people; creating experimental "markets" for health states is a theoretically attractive way to address this. We explore the possibility that this framework may be fundamentally flawed-because there may not be any stable values to be revealed. Instead, perhaps people construct ad hoc values, influenced by contextual factors, such as the observed decisions of others.
  
  
  METHODS
  The participants bid to buy relief from equally painful electrical shocks to the leg and arm in an experimental health market based on an interactive second-price auction. Thirty subjects were randomly assigned to two experimental conditions where the bids by "others" were manipulated to follow increasing or decreasing price trends for one, but not the other, pain. After the auction, a preference test asked the participants to choose which pain they prefer to experience for a longer duration.
  
  
  RESULTS
  Players remained indifferent between the two pain-types throughout the auction. However, their bids were differentially attracted toward what others bid for each pain, with overbidding during decreasing prices and underbidding during increasing prices.
  
  
  CONCLUSIONS
  Health preferences are dissociated from market prices, which are strongly referenced to others' choices. This suggests that the price of health care in a free-market has the capacity to become critically detached from people's underlying preferences.
authors.affiliation: Centre for Health Policy and Department of Surgery and Cancer, Imperial College London.
authors.forename: Ivo
authors.initials: I
authors.lastname: Vlaev
authors.affiliation: Department of Clinical Neurosciences, University of Cambridge, Addenbrookes Hospital.
authors.forename: Ben
authors.initials: B
authors.lastname: Seymour
authors.affiliation: Centre for Behavioural Sciences, Warwick Business School, University of Warwick.
authors.forename: Nick
authors.initials: N
authors.lastname: Chater
authors.affiliation: Centre for Neuroimaging, Institute of Neurology, University College London.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Winston
authors.affiliation: Centre for Neuroimaging, Institute of Neurology, University College London.
authors.forename: Wako
authors.initials: W
authors.lastname: Yoshida
authors.affiliation: Centre for Neuroimaging, Institute of Neurology, University College London.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wright
authors.affiliation: Centre for Neuroimaging, Institute of Neurology, University College London.
authors.forename: Mkael
authors.initials: M
authors.lastname: Symmonds
authors.affiliation: Centre for Neuroimaging, Institute of Neurology, University College London.
authors.forename: Ray
authors.initials: R
authors.lastname: Dolan
mesh_terms: D000328:Adult; D003132:Commerce / Q000706:statistics & numerical data*; D003258:Consumer Behavior; D003657:Decision Making; D005260:Female; D006291:Health Policy; D006801:Humans; D008297:Male; D008389:Marketing of Health Services; D010146:Pain / Q000517:prevention & control*; D012919:Social Behavior; D055815:Young Adult