Saturday, April 01, 2006

The unnecessary hypothesis

Does prayer work? The New Testament is clear that it should: "Ask and it shall be given you" (Matthew 7:7). Other religions would concur. However, evidence for this prediction has been hard to come by. Francis Galton was perhaps the first to approach this problem scientifically. In his Statistical inquiries into the efficacy of prayer (1872) he wrote:
"The efficacy of prayer [...] is a perfectly appropriate and legitimate subject of scientific inquiry. Whether prayer is efficacious or not, in any given sense, is a matter of fact on which each man must form an opinion for himself. His decision will lie based upon data more or less justly handled, according to his education and habits. An unscientific reasoner will be guided by a confused recollection of crude experience. A scientific reasoner will scrutinise each separate experience before he admits it as evidence, and will compare all the cases he has selected on a methodical system."
Galton, one of the founders of modern statistics, was clear about how to proceed. He began by reducing the problem to "a simple statistical question -- are prayers answered, or are they not?" He then argued that one should "examine large classes of cases, and to be guided by broad averages". In a memorable case study, Galton considered the "longevity of persons whose lives are prayed for":
"The public prayer for the sovereign of every state, Protestant and Catholic, is and has been in the spirit of our own, "Grant her in health long to live." Now, as a simple matter of fact, has this prayer any efficacy? There is a memoir by Dr. Guy, in the (Vol. XXII. p.355), in which he compares the mean age of sovereigns with that of other classes of persons [...] The sovereigns are literally the shortest lived of all who have the advantage of affluence. The prayer has therefore no efficacy, unless the very questionable hypothesis be raised, that the conditions of royal life may naturally be yet more fatal, and that their influence is partly, though incompletely, neutralised by the effects of public prayers."
Many studies have since attempted to detect the effects of prayer in a variety of contexts, using a Galtonian approach.

The results of the largest study to date into the clinical effects of intercessory prayer were published in the American Heart Journal last week. Rhosgobel wrote an excellent summary of the research. Galton would have been proud. The study split over 1800 coronary bypass patients into three groups:
  1. Patients who were prayed for but were told that they "may or may not be prayed for"
  2. Patients who were not prayed for but were told that they "may or may not be prayed for"
  3. Patients who were prayed for and were told that they "will be prayed for"
Patients from the first two groups did not differ in the probability of developing complications within 30 days of the surgery. Patients from group 3 showed a small but statistically significant increase (!) in complications. The study cost approximately $2.4 million, mostly from the Templeton Foundation. "Unscientific reasoners" have already started to make up excuses, in much the same way as defenders of alternative medicine.

After reading Laplace's Mécanique céleste, Napoleon is said to have questioned the author on his failure to mention God. Laplace famously replied: "I have no need for such a hypothesis". I agree.